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• Oracle pl\sql question for my homework in oracle 11G class [migrated]

  - by Bjolds

  I am new to oracle 11G programming and i have run into a tough situation with pl\sql funtions and automation. I ame unsure how to create the function for the automation of Registration system for a College registration system. Here is what i want to do. I want to automate the registrations system so that it automaticly registers students. Then I want a procedure to automate the grading system. I have included the code that i am written to make most of this assignment work which it does but unsure how to incorporate Pl\SQL automated fuctions for the registrations system, and the grading system. So Any help or Ideas I would greatly appreciate please. set Linesize 250 set pagesize 150 drop table student; drop table faculty; drop table Course; drop table Section; drop table location; DROP TABLE courseInstructor; DROP TABLE Registration; DROP TABLE grade; create table student( studentid number(10), Lastname varchar2(20), Firstname Varchar2(20), MI Char(1), address Varchar2(20), city Varchar2(20), state Char(2), zip Varchar2(10), HomePhone Varchar2(10), Workphone Varchar2(10), DOB Date, Pin VARCHAR2(10), Status Char(1)); ALTER TABLE Student Add Constraint Student_StudentID_pk Primary Key (studentID); Insert into student values (1,'xxxxxxxx','xxxxxxxxxx','x','xxxxxxxxxxxxxxx','Columbus','oh','44159','xxx-xxx-xxxx','xxx-xxx-xxxx','06-Mar-1957','1211','c'); create table faculty( FacultyID Number(10), FirstName Varchar2(20), Lastname Varchar2(20), MI Char(1), workphone Varchar2(10), CellPhone Varchar2(10), Rank Varchar2(20), Experience Varchar2(10), Status Char(1)); ALTER TABLE Faculty ADD Constraint Faculty_facultyId_PK PRIMARY KEY (FacultyID); insert into faculty values (1,'xxx','xxxxxxxxxxxx',xxx-xxx-xxxx','xxx-xxx-xxxx','professor','20','f'); create table Course( CourseId number(10), CourseNumber Varchar2(20), CourseName Varchar(20), Description Varchar(20), CreditHours Number(4), Status Char(1)); ALTER TABLE Course ADD Constraint Course_CourseID_pk PRIMARY KEY(CourseID); insert into course values (1,'cit 100','computer concepts','introduction to PCs','3.0','o'); insert into course values (2,'cit 101','Database Program','Database Programming','4.0','o'); insert into course values (3,'Math 101','Algebra I','Algebra I Concepts','5.0','o'); insert into course values (4,'cit 102a','Pc applications','Aplications 1','3.0','o'); insert into course values (5,'cit 102b','pc applications','applications 2','3.0','o'); insert into course values (6,'cit 102c','pc applications','applications 3','3.0','o'); insert into course values (7,'cit 103','computer concepts','introduction systems','3.0','c'); insert into course values (8,'cit 110','Unified language','UML design','3.0','o'); insert into course values (9,'cit 165','cobol','cobol programming','3.0','o'); insert into course values (10,'cit 167','C++ Programming 1','c++ programming','4.0','o'); insert into course values (11,'cit 231','Expert Excel','spreadsheet apps','3.0','o'); insert into course values (12,'cit 233','expert Access','database devel.','3.0','o'); insert into course values (13,'cit 169','Java Programming I','Java Programming I','3.0','o'); insert into course values (14,'cit 263','Visual Basic','Visual Basic Prog','3.0','o'); insert into course values (15,'cit 275','system analysis 2','System Analysis 2','3.0','o'); create table Section( SectionID Number(10), CourseId Number(10), SectionNumber VarChar2(10), Days Varchar2(10), StartTime Date, EndTime Date, LocationID Number(10), SeatAvailable Number(3), Status Char(1)); ALTER TABLE Section ADD Constraint Section_SectionID_PK PRIMARY KEY(SectionID); insert into section values (1,1,'18977','r','21-Sep-2011','10-Dec-2011','1','89','o'); create table Location( LocationId Number(10), Building Varchar2(20), Room Varchar2(5), Capacity Number(5), Satus Char(1)); ALTER TABLE Location ADD Constraint Location_LocationID_pk PRIMARY KEY (LocationID); insert into Location values (1,'Clevleand Hall','cl209','35','o'); insert into Location values (2,'Toledo Circle','tc211','45','o'); insert into Location values (3,'Akron Square','as154','65','o'); insert into Location values (4,'Cincy Hall','ch100','45','o'); insert into Location values (5,'Springfield Dome','SD','35','o'); insert into Location values (6,'Dayton Dorm','dd225','25','o'); insert into Location values (7,'Columbus Hall','CB354','15','o'); insert into Location values (8,'Cleveland Hall','cl204','85','o'); insert into Location values (9,'Toledo Circle','tc103','75','o'); insert into Location values (10,'Akron Square','as201','46','o'); insert into Location values (11,'Cincy Hall','ch301','73','o'); insert into Location values (12,'Dayton Dorm','dd245','57','o'); insert into Location values (13,'Springfield Dome','SD','65','o'); insert into Location values (14,'Cleveland Hall','cl241','10','o'); insert into Location values (15,'Toledo Circle','tc211','27','o'); insert into Location values (16,'Akron Square','as311','28','o'); insert into Location values (17,'Cincy Hall','ch415','73','o'); insert into Location values (18,'Toledo Circle','tc111','67','o'); insert into Location values (19,'Springfield Dome','SD','69','o'); insert into Location values (20,'Dayton Dorm','dd211','45','o'); Alter Table Student Add Constraint student_Zip_CK Check(Rtrim (Zip,'1234567890-') is null); Alter Table Student ADD Constraint Student_Status_CK Check(Status In('c','t')); Alter Table Student ADD Constraint Student_MI_CK2 Check(RTRIM(MI,'abcdefghijklmnopqrstuvwxyz')is Null); Alter Table Student Modify pin not Null; Alter table Faculty Add Constraint Faculty_Status_CK Check(Status In('f','a','i')); Alter table Faculty ADD Constraint Faculty_Rank_CK Check(Rank In ('professor','doctor','instructor','assistant','tenure')); Alter table Faculty ADD Constraint Faculty_MI_CK2 Check(RTRIM(MI,'abcdefghijklmnopqrstuvwxyz')is Null); Update Section Set Starttime = To_date('09-21-2011 6:00 PM', 'mm-dd-yyyy hh:mi pm'); Update Section Set Endtime = To_date('12-10-2011 9:50 PM', 'mm-dd-yyyy hh:mi pm'); alter table Section Add Constraint StartTime_Status_CK Check (starttime < Endtime); Alter Table Section Add Constraint Section_StartTime_ck check (StartTime < EndTime); Alter Table Section ADD Constraint Section_CourseId_FK FOREIGN KEY (CourseID) References Course(CourseId); Alter Table Section ADD Constraint Section_LocationID_FK FOREIGN KEY (LocationID) References Location (LocationId); Alter Table Section ADD Constraint Section_Days_CK Check(RTRIM(Days,'mtwrfsu')IS Null); update section set seatavailable = '99'; Alter Table Section ADD Constraint Section_SeatsAvailable_CK Check (SeatAvailable < 100); Alter Table Course Add Constraint Course_CreditHours_ck check(CreditHours < = 6.0); update location set capacity = '99'; Alter Table Location Add Constraint Location_Capacity_CK Check(Capacity < 100); Create Table Registration ( StudentID Number(10), SectionID Number(10), Constraint Registration_pk Primary key (studentId, Sectionid)); Insert into registration values (1, 2); Insert into Registration values (2, 3); Insert into registration values (3, 4); Insert into registration values (4, 5); Insert into registration values (5, 6); Insert into registration values (6, 7); Insert into registration values (7, 8); Insert into registration values (8, 9); insert into registration values (9, 10); insert into registration values (10, 11); insert into registration values (9, 12); insert into registration values (8, 13); insert into registration values (7, 14); insert into registration values (6, 15); insert into registration values (5, 17); insert into registration values (4, 18); insert into registration values (3, 19); insert into registration values (2, 20); insert into registration values (1, 21); insert into registration values (2, 22); insert into registration values (3, 23); insert into registration values (4, 24); insert into registration values (5, 25); Insert into registration values (6, 24); insert into registration values (7, 23); insert into registration values (8, 22); insert into registration values (9, 21); insert into registration values (10, 20); insert into registration values (9, 19); insert into registration values (8, 17); Create Table courseInstructor( FacultyID Number(10), SectionID Number(10), Constraint CourseInstructor_pk Primary key (FacultyId, SectionID)); insert into courseInstructor values (1, 1); insert into courseInstructor values (2, 2); insert into courseInstructor values (3, 3); insert into courseInstructor values (4, 4); insert into courseInstructor values (5, 5); insert into courseInstructor values (5, 6); insert into courseInstructor values (4, 7); insert into courseInstructor values (3, 8); insert into courseInstructor values (2, 9); insert into courseInstructor values (1, 10); insert into courseInstructor values (5, 11); insert into courseInstructor values (4, 12); insert into courseInstructor values (3, 13); insert into courseInstructor values (2, 14); insert into courseInstructor values (1, 15); Create table grade( StudentID Number(10), SectionID Number(10), Grade Varchar2(1), Constraint grade_pk Primary key (StudentID, SectionID)); CREATE OR REPLACE TRIGGER TR_CreateGrade AFTER INSERT ON Registration FOR EACH ROW BEGIN INSERT INTO grade (SectionID,StudentID,Grade) VALUES(:New.SectionID,:New.StudentID,NULL); END TR_createGrade; / CREATE OR REPLACE FORCE VIEW V_reg_student_course AS SELECT Registration.StudentID, student.LastName, student.FirstName, course.CourseName, Registration.SectionID, course.CreditHours, section.Days, TO_CHAR(StartTime, 'MM/DD/YYYY') AS StartDate, TO_CHAR(StartTime, 'HH:MI PM') AS StartTime, TO_CHAR(EndTime, 'MM/DD/YYYY') AS EndDate, TO_CHAR(EndTime, 'HH:MI PM') AS EndTime, location.Building, location.Room FROM registration, student, section, course, location WHERE registration.StudentID = student.StudentID AND registration.SectionID = section.SectionID AND section.LocationID = location.LocationID AND section.CourseID = course.CourseID; CREATE OR REPLACE FORCE VIEW V_teacher_to_course AS SELECT courseInstructor.FacultyID, faculty.FirstName, faculty.LastName, courseInstructor.SectionID, section.Days, TO_CHAR(StartTime, 'MM/DD/YYYY') AS StartDate, TO_CHAR(StartTime, 'HH:MI PM') AS StartTime, TO_CHAR(EndTime, 'MM/DD/YYYY') AS EndDate, TO_CHAR(EndTime, 'HH:MI PM') AS EndTime, location.Building, location.Room FROM courseInstructor, faculty, section, course, location WHERE courseInstructor.FacultyID = faculty.FacultyID AND courseInstructor.SectionID = section.SectionID AND section.LocationID = location.LocationID AND section.CourseID = course.CourseID; SELECT * FROM V_reg_student_course; SELECT * FROM V_teacher_to_course;

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• C string question

  - by user208454

  I am writing a simple c program which reverses a string, taking the string from argv[1]. Here is the code: #include <stdio.h> #include <stdlib.h> #include <string.h> char* flip_string(char *string){ int i = strlen(string); int j = 0; // Doesn't really matter all I wanted was the same size string for temp. char* temp = string; puts("This is the original string"); puts(string); puts("This is the \"temp\" string"); puts(temp); for(i; i>=0; i--){ temp[j] = string[i] if (j <= strlen(string)) { j++; } } return(temp); } int main(int argc, char *argv[]){ puts(flip_string(argv[1])); printf("This is the end of the program\n"); } That's basically it, the program compiles and everything but does not return the temp string in the end (just blank space). In the beginning it prints temp fine when its equal to string. Furthermore if I do a character by character printf of temp in the for loop the correct temp string in printed i.e. string - reversed. just when I try to print it to standard out (after the for loop/ or in the main) nothing happens only blank space is printed.

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• alot questings since i wanted to make a new SSB game or mario game(that use 3d models) [closed]

  - by user20465

  i have just started to study programming and i know already ppl will say why make a so big project like as a SSB game for a noob game development? cuz i always wanted a SSB engine like as Mugen is a fighter game engine but is not like as SSB´s gameplay + is not using 3d models too so i will call it SSBmugen(until i find a better title for it i got afew ideas for titles) also i wanted to make this game so it can use SSBbrawl files(models+animations mainly) the moveset+Stage coding files i wanted to redo cuz so anything can be possible like make a teleporter or a pipe teleporter(like as Super mario bros game) on a stag e or make some stuff there is impossible in SSBbrawl for moveset coding but is not in SSBmugen like make so a char. summon a Clone and the clone will do a attack and then is gone or some attacks/moves also i will make a moveset/stage Coding editor so it will be really easy to make moveset/stages coding for yours 3d models/animations moveset+stage Coding i mean: hitboxes/hurtboxes/moving Stuff/moving bones like cape or hair bones that is moving by wind effects or falling or other stuff like that/other stuff that needed to be coded i have planed to make a editor(for moveset/char. coding) or add the editor in brawlbox for my game so other ppl can easy make moveset/stages Coding to they´s models/animations so it will be easy so even kids can make a custom movesets/stages why using SSBbrawl files?: cuz ppl have made alot of models or textures/custom movesets/custom stages like goku/other anime/not brawl stuff for super smash bros brawl hacking(a.k.a modding) so ppl dont have to redo anything if they wanted to have the custom models or textures/custom movesets/custom stages from SSBbrawl to SSBmugen +there is the program named brawlbox that can open brawl files like model/animations and can edit models or animations and import models from 3ds max to be the right model format for SSBbrawl and i also wanted it so easy to add(a.k.a installer) Recolours or alt. models(like as oneslot doctor mario model over mario´s boneset) or textures/Movesets/new char. slots/new stages so easy so you only needing to download themplace them in right foldername them the right nameStart the gameRecolours or alt. models or textures/Movesets/new char. slots/new stages works an loading right so you wont needing to edit any files for add something so kids/not so smart ppl can easy use the mods other ppl is making/uploading for this game here is the file format i wanted to know if they can be readed/opened if making a game that use these files: .mld0(brawl model file) .chr0(model animation for moving/scale/rota the bones) .srt0(animations for texture like moving eyes or blinking) .vis0(Animations for get polygons to hide/show with visibilitybones on the model there is also some polygons there ) .brres(a file format where stuff like model files or textures or animations is inside) .pac(a file format where the .brres is inside to keep model+textures+model for the shadow in 1 file) .wav (for SoundFX effects or voices to char. or stages) i am sure that one is possible the .wav files is inside a other file format for brawl but that file can´t you add more .wav files inside only replace so i wanted the .wav files outside so its easy to add/replace/remove SoundFX effects or voices to char. or stages .brstm(brawl music file so the music is looped perfect so it loop in middel of the music and not start over again then the music is done) afew more file formats (mainly for the Graphics effects like fire/aura/hit effects if not needing to redo them)so only coding in the editor i will make is needed to be done for port a SSBB hack(a.k.a mod)(moveset/stage coding) to this game wanted the game to be able to load these files and load them right like if loading wait1.chr0(idle animation) it will also load at same time wait1.srt0/wait1.vis0 and all kinda of animations is inside the same .brres file i am needing since it to be able to load the file format i wanted cuz: -the animations can´t be converted to any other animation file format and i dont think ppl want to redo these animations(inc. me for Goku to SSBbrawl) -models can be converted but then they lose all the shader/materials stuff like a shine effect or lighting on the model -.brstm can be converted to .wav but then there will be no loop so i prefer it can load this file format too for the music to stage/menu -brawlbox is really easy to use for make animation for the char. and import models from 3ds max so even around "not too stupid" 10 year kids can make SSBB mods(not try to be rude but to say how easy it is) also i wanted the folder setup for characters/stages/moveset/other stuff to be like this: https://www.dropbox.com/s/2oolm5z5ri234tz/SSBmugen%20Folder%20setup.txt just uploaded a txt file since it is a wall of text and this post is already a wall of test so it easy to place stuff (if not i do a program for to that so it auto place the stuff on right place) not 100% sure what to use of game engine to make this possible but i got a dll file from that brawlbox program that can open/read/edit these file formats if that helps i also got open source of brawlbox i have kinda learned programming(since its kinda the same thing but still not 100% same) from Super smash bros modding/hacking like coding a moveset for the new animations/models + have readed alittle about it but i am soon starting for real to study it for ppl who is alittle confuse for what i am asking for here is the list: -what game engine should i use to make a SSB clone? but at same time to make all this stuff i just said possible so ppl can make they own mods and share them and use the already made mods from SSBbrawl? and easy to use aswell so noob programmors can use it? -where to learning programming on internet to be even more ready to make a game like this? and dont wanted to start in the small like making small boring 2d games that no one care about anyway ps. i am also planing a other project like as SSBmugen but it will be Super mario bros open (again tittle unsure but open means open source) i will make a Mario game engine that also use 3d models and can have 2d or 3d gameplay with any mario powerups/gameplay(from any mario platform games) there is ever made multiplayer like as in New super mario bros wii maybe multiplay over lan or online but for now over 1 PC also alittle planed for that to my SSBmugen a Level/world map editor for it too(easy to use so even kids can use it and make levels for it) so it just place the objects/enemies and options for them enemies since they are not 100% same AI in all mario game like to choose a goomba have AI from SM64 the Editor will be able to change the gameplay on a level while have a other gameplay on a other level like this: 1 level have Super mario bros 3 gameplay (then it will be a 3d model remake) a other level have super mario galaxy gameplay but in a Super mario 3d land level yet a other level have super mario 64 gameplay but with powerups from a other mario game like powerups from mario 3d land or can ride on Yoshi so you can easy remake your fav. level from a old mario game in this mario engine/editor or just make a custom one with yours fav. mario gameplay/powerups so it will be like turn off/on: walljump/triple jump/other kinda or jumps/2x punch and 1 kick+Air kick/SMG spin attack/Fludd/other stuff like that so you can make the gameplay from the first mario game to the newest or make custom gameplay on a level also the star(from 64/sunshine/galaxy) will be replaced with the flag from new super mario bros/mario 3d land since the game is not so much about getting stars its more about making/download the levels you wanted and share them to other ppl and play these level so after have killed like the boss from SM64 bomb omb field(if one have made that) you will get the flag instead of star since i wanted it to be simple to make levels in the editor to make the bosses/new enemies/new powerups/custom char. idk what to do to make that simple yet also thinking the mario game will use brawl files since it almost already got all needed animations/models for this since i dont wanted to redo animations/models and if needing more animations i can just make them easy in brawlbox since thats the program i am most used to make animations but that will be after my SSBmugen project if not this game will be easyer then SSBmugen to make since i am planing then 1 of them is done i use the that game as base to make the other (since both is kinda platfrom games and possible using same file format for both) also wanted to ask what is best to start with out of these 2 games? also will maybe make a DLC site(or ingame) for both of these games if they get done so it wont end up like as Mugen where you needing to look all over the internet to find the stuff you wanted but for my game all the mods for my game is on same place not sure about online mode for SSBmugen or super mario bros open but i can always add that then i get better at programming both games also need to have options on controls/if using joystick also that i have planed these game for a long time and got even more ideas for them but first i wanted to get them to work so i can add the other stuff later(like DLC or online mode or some other stuff later) right now i know 0,0001% to programming(in my option) maybe i know more then that since i have been study it alittle but i learning while making stuff like this that was also my plan for make these game learn while making them and get better to programming so again i say it i kinda dont want to hear dont do these projects cuz i already know it will be hard so dont wanted so much to heard stuff like: you can´t do it since you just started learning programming or this project will fail since somewhere i needing to get started with programming and this is where i want to start to make my dream games(possible other´s dream games too) and i dont think this project will fail if i work hard on it (as i possible will) and ppl will maybe help i think this was all my questing/ideas for now (sorry for it sounds more like ideas then questings) but i needing to say my ideas so you ppl can see what i needing to use for make this possible

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• Dynamic libraries are not allowed on iOS but what about this?

  - by tapirath

  I'm currently using LuaJIT and its FFI interface to call C functions from LUA scripts. What FFI does is to look at dynamic libraries' exported symbols and let the developer use it directly form LUA. Kind of like Python ctypes. Obviously using dynamic libraries is not permitted in iOS for security reasons. So in order to come up with a solution I found the following snippet. /* (c) 2012 +++ Filip Stoklas, aka FipS, http://www.4FipS.com +++ THIS CODE IS FREE - LICENSED UNDER THE MIT LICENSE ARTICLE URL: http://forums.4fips.com/viewtopic.php?f=3&t=589 */ extern "C" { #include <lua.h> #include <lualib.h> #include <lauxlib.h> } // extern "C" #include <cassert> // Please note that despite the fact that we build this code as a regular // executable (exe), we still use __declspec(dllexport) to export // symbols. Without doing that FFI wouldn't be able to locate them! extern "C" __declspec(dllexport) void __cdecl hello_from_lua(const char *msg) { printf("A message from LUA: %s\n", msg); } const char *lua_code = "local ffi = require('ffi') \n" "ffi.cdef[[ \n" "const char * hello_from_lua(const char *); \n" // matches the C prototype "]] \n" "ffi.C.hello_from_lua('Hello from LUA!') \n" // do actual C call ; int main() { lua_State *lua = luaL_newstate(); assert(lua); luaL_openlibs(lua); const int status = luaL_dostring(lua, lua_code); if(status) printf("Couldn't execute LUA code: %s\n", lua_tostring(lua, -1)); lua_close(lua); return 0; } // output: // A message from LUA: Hello from LUA! Basically, instead of using a dynamic library, the symbols are exported directly inside the executable file. The question is: is this permitted by Apple? Thanks.

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• In MMO game, how to handle user characters, who are offline?

  - by Deele

  In my medieval MMO game, players have their own character, that represents themselves inside game. Like a King. Players could have cities and armies, but King acts as main driving force. Then it comes to player, going offline/vacation/disconnect. How to deal with "offline King", to keep some sort of reality in game, without ruining everything for player. I have never liked unrealistic stuff in games, like appearing/dissapearing from thin air, like in WoW or other MMO RPG's, when it comes to connect/disconnect, like in Matrix movie, when you are disconnected, your "avatar" inside the system just vaninshes. Ok, if player char stays where it was left, other players who are online could kick his ass like offline player char was frozen? I see only one solution - give player char, while offline, some sort of AI, that controls char. Is there any other solutions? May be, some sort of legend/story, could make users only as inner-voice, leaving King just passively controlled by user, or other stuff... Please, help! I hope you understand my question.

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• Problem inserting pre-ordered values to quadtree

  - by Lucas Corrêa Feijó

  There's this string containing B, W and G (standing for black, white and gray). It defines the pre-ordered path of the quadtree I want to build. I wrote this method for filling the QuadTree class I also wrote but it doesn't work, it inserts correctly until it reaches a point in the algorithm it needs to "return". I use math quadrants convention order for insertion, such as northeast, northwest, southwest and southeast. A quadtree has all it's leafs black or white and all the other nodes gray The node used in the tree is called Node4T and has a char as data and 4 references to other nodes like itself, called, respectively NE, NW, SW, SE. public void insert(char val) { if(root==null) { root = new Node4T(val); } else { insert(root, val); } } public void insert(Node4T n, char c) { if(n.data=='G') // possible to insert { if(n.NE==null) { n.NE = new Node4T(c); return; } else { insert(n.NE,c); } if(n.NW==null) { n.NW = new Node4T(c); return; } else { insert(n.NW,c); } if(n.SW==null) { n.SW = new Node4T(c); return; } else { insert(n.SW,c); } if(n.SE==null) { n.SE = new Node4T(c); return; } else { insert(n.SE,c); } } else // impossible to insert { } } The input "GWGGWBWBGBWBWGWBWBWGGWBWBWGWBWBGBWBWGWWWB" is given a char at a time to the insert method and then the print method is called, pre-ordered, and the result is "GWGGWBWBWBWGWBWBW". How do I make it import the string correctly? Ignore the string reading process, suppose the method is called and it has to do it's job.

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• strlen returns incorrect value when called in gdb

  - by alesplin

  So I'm noticing some severely incorrect behavior from calls to standard library functions inside GDB. I have the following program to illustrate: #include <stdio.h> #include <stdlib.h> #include <string.h> int main(int argc, char *argv[]) { char *s1 = "test"; char *s2 = calloc(strlen("test")+1,sizeof(char)); snprintf(s2,strlen("test")+1,"test"); printf("string constant: %lu\n", strlen(s1)); printf("allocated string: %lu\n", strlen(s2)); free(s2); return 0; } When run from the command-line, this program outputs just what you'd expect: string constant: 4 allocated string: 4 However, in GDB, I get the following, incorrect output from calls to strlen(): (gdb) p strlen(s1) $1 = -938856896 (gdb) p strlen(s2) $2 = -938856896 I'm pretty sure this is a problem with glibc shipped with Ubuntu (I'm using 10.10), but this is a serious problem for those of us who spend lots of time in GDB. Is anyone else experiencing this kind of error? What's the best way to fix it? Build glibc from source? (I'm already running a version of GDB built from source)

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• Convert Decimal to ASCII

  - by Dan Snyder

  I'm having difficulty using reinterpret_cast. Before I show you my code I'll let you know what I'm trying to do. I'm trying to get a filename from a vector full of data being used by a MIPS I processor I designed. Basically what I do is compile a binary from a test program for my processor, dump all the hex's from the binary into a vector in my c++ program, convert all of those hex's to decimal integers and store them in a DataMemory vector which is the data memory unit for my processor. I also have instruction memory. So When my processor runs a SYSCALL instruction such as "Open File" my C++ operating system emulator receives a pointer to the beginning of the filename in my data memory. So keep in mind that data memory is full of ints, strings, globals, locals, all sorts of stuff. When I'm told where the filename starts I do the following: Convert the whole decimal integer element that is being pointed to to its ASCII character representation, and then search from left to right to see if the string terminates, if not then just load each character consecutively into a "filename" string. Do this until termination of the string in memory and then store filename in a table. My difficulty is generating filename from my memory. Here is an example of what I'm trying to do: C++ Syntax (Toggle Plain Text) 1.Index Vector NewVector ASCII filename 2.0 240faef0 128123792 'abc7' 'a' 3.0 240faef0 128123792 'abc7' 'ab' 4.0 240faef0 128123792 'abc7' 'abc' 5.0 240faef0 128123792 'abc7' 'abc7' 6.1 1234567a 243225 'k2s0' 'abc7k' 7.1 1234567a 243225 'k2s0' 'abc7k2' 8.1 1234567a 243225 'k2s0' 'abc7k2s' 9. //EXIT LOOP// 10.1 1234567a 243225 'k2s0' 'abc7k2s' Index Vector NewVector ASCII filename 0 240faef0 128123792 'abc7' 'a' 0 240faef0 128123792 'abc7' 'ab' 0 240faef0 128123792 'abc7' 'abc' 0 240faef0 128123792 'abc7' 'abc7' 1 1234567a 243225 'k2s0' 'abc7k' 1 1234567a 243225 'k2s0' 'abc7k2' 1 1234567a 243225 'k2s0' 'abc7k2s' //EXIT LOOP// 1 1234567a 243225 'k2s0' 'abc7k2s' Here is the code that I've written so far to get filename (I'm just applying this to element 1000 of my DataMemory vector to test functionality. 1000 is arbitrary.): C++ Syntax (Toggle Plain Text) 1.int i = 0; 2.int step = 1000;//top->a0; 3.string filename; 4.char *temp = reinterpret_cast<char*>( DataMemory[1000] );//convert to char 5.cout << "a0:" << top->a0 << endl;//pointer supplied 6.cout << "Data:" << DataMemory[top->a0] << endl;//my vector at pointed to location 7.cout << "Data(1000):" << DataMemory[1000] << endl;//the element I'm testing 8.cout << "Characters:" << &temp << endl;//my temporary char array 9. 10.while(&temp[i]!=0) 11.{ 12. filename+=temp[i];//add most recent non-terminated character to string 13. i++; 14. if(i==4)//when 4 chatacters have been added.. 15. { 16. i=0; 17. step+=1;//restart loop at the next element in DataMemory 18. temp = reinterpret_cast<char*>( DataMemory[step] ); 19. } 20. } 21. cout << "Filename:" << filename << endl; int i = 0; int step = 1000;//top-a0; string filename; char *temp = reinterpret_cast( DataMemory[1000] );//convert to char cout << "a0:" << top-a0 << endl;//pointer supplied cout << "Data:" << DataMemory[top-a0] << endl;//my vector at pointed to location cout << "Data(1000):" << DataMemory[1000] << endl;//the element I'm testing cout << "Characters:" << &temp << endl;//my temporary char array while(&temp[i]!=0) { filename+=temp[i];//add most recent non-terminated character to string i++; if(i==3)//when 4 chatacters have been added.. { i=0; step+=1;//restart loop at the next element in DataMemory temp = reinterpret_cast( DataMemory[step] ); } } cout << "Filename:" << filename << endl; So the issue is that when I do the conversion of my decimal element to a char array I assume that 8 hex #'s will give me 4 characters. Why isn't this this case? Here is my output: C++ Syntax (Toggle Plain Text) 1.a0:0 2.Data:0 3.Data(1000):4428576 4.Characters:0x7fff5fbff128 5.Segmentation fault

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• C++: Simplifying my program to convert numbers to from one base to another.

  - by Spin City

  Hello, I'm taking a beginner C++ course. I received an assignment telling me to write a program that converts an arbitrary number from any base between binary and hex to another base between binary and hex. I was asked to use separate functions to convert to and from base 10. It was to help us get used to using arrays. (We already covered passing by reference previously in class.) I already turned this in, but I'm pretty sure this wasn't how I was meant to do it: #include <iostream> #include <conio.h> #include <cstring> #include <cmath> using std::cout; using std::cin; using std::endl; int to_dec(char value[], int starting_base); char* from_dec(int value, int ending_base); int main() { char value[30]; int starting_base; int ending_base; cout << "This program converts from one base to another, so long as the bases are" << endl << "between 2 and 16." << endl << endl; input_numbers: cout << "Enter the number, then starting base, then ending base:" << endl; cin >> value >> starting_base >> ending_base; if (starting_base < 2 || starting_base > 16 || ending_base < 2 || ending_base > 16) { cout << "Invalid base(s). "; goto input_numbers; } for (int i=0; value[i]; i++) value[i] = toupper(value[i]); cout << "Base " << ending_base << ": " << from_dec(to_dec(value, starting_base), ending_base) << endl << "Press any key to exit."; getch(); return 0; } int to_dec(char value[], int starting_base) { char hex[16] = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'}; long int return_value = 0; unsigned short int digit = 0; for (short int pos = strlen(value)-1; pos > -1; pos--) { for (int i=0; i<starting_base; i++) { if (hex[i] == value[pos]) { return_value+=i*pow((float)starting_base, digit++); break; } } } return return_value; } char* from_dec(int value, int ending_base) { char hex[16] = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'}; char *return_value = (char *)malloc(30); unsigned short int digit = (int)ceil(log10((double)(value+1))/log10((double)ending_base)); return_value[digit] = 0; for (; value != 0; value/=ending_base) return_value[--digit] = hex[value%ending_base]; return return_value; } I'm pretty sure this is more advanced than it was meant to be. How do you think I was supposed to do it? I'm essentially looking for two kinds of answers: Examples of what a simple solution like the one my teacher probably expected would be. Suggestions on how to improve the code.

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• Linked lists in Java - Help with writing methods

  - by user368241

  Representation of a string in linked lists In every intersection in the list there will be 3 fields : The letter itself. The number of times it appears consecutively. A pointer to the next intersection in the list. The following class CharNode represents a intersection in the list : public class CharNode { private char _data; private int _value; private charNode _next; public CharNode (char c, int val, charNode n) { _data = c; _value = val; _next = n; } public charNode getNext() { return _next; } public void setNext (charNode node) { _next = node; } public int getValue() { return _value; } public void setValue (int v) { value = v; } public char getData() { return _data; } public void setData (char c) { _data = c; } } The class StringList represents the whole list : public class StringList { private charNode _head; public StringList() { _head = null; } public StringList (CharNode node) { _head = node; } } Add methods to the class StringList according to the details : (I will add methods gradually according to my specific questions) (Pay attention, these are methods from the class String and we want to fulfill them by the representation of a string by a list as explained above) Pay attention to all the possible error cases. Write what is the time complexity and space complexity of every method that you wrote. Make sure the methods you wrote are effective. It is NOT allowed to use ready classes of Java. It is NOT allowed to move to string and use string operations. 1) public int indexOf (int ch) - returns the index in the string it is operated on of the first appeareance of the char "ch". If the char "ch" doesn't appear in the string, returns -1. If the value of fromIndex isn't in the range, returns -1. Here is my try : public int indexOf (int ch) { int count = 0; charNode pos = _head; if (pos == null ) { return -1; } for (pos = _head; pos!=null && pos.getData()!=ch; pos = pos.getNext()) { count = count + pos.getValue(); } if (pos==null) return -1; return count; } Time complexity = O(N) Space complexity = O(1) EDIT : I have a problem. I tested it in BlueJ and if the char ch doesn't appear it returns -1 but if it does, it always returns 0 and I don't understand why... I am confused. How can the compiler know that the value is the number of times the letter appears consecutively? Can I assume this because its given on the question or what? If it's true and I can assume this, then my code should be correct right? Ok I just spoke with my instructor and she said it isn't required to write it in the exercise but in order for me to test that it indeed works, I need to open a new class and write a code for making a list so that the the value of every node is the number of times the letter appears consecutively. Can someone please assist me? So I will copy+paste to BlueJ and this way I will be able to test all the methods. Meanwhile I am moving on to the next methods. 2) public int indexOf (int ch, int fromIndex) - returns the index in the string it is operated on of the first appeareance of the char "ch", as the search begins in the index "fromIndex". If the char "ch" doesn't appear in the string, returns -1. If the value of fromIndex doesn't appear in the range, returns -1. Here is my try: public int indexOf (int ch, int fromIndex) { int count = 0, len=0, i; charNode pos = _head; CharNode cur = _head; for (pos = _head; pos!=null; pos = pos.getNext()) { len = len+1; } if (fromIndex<0 || fromIndex>=len) return -1; for (i=0; i<fromIndex; i++) { cur = cur.getNext(); } if (cur == null ) { return -1; } for (cur = _head; cur!=null && cur.getData()!=ch; cur = cur.getNext()) { count = count + cur.getValue(); } if (cur==null) return -1; return count; } Time complexity = O(N) ? Space complexity = O(1) 3) public StringList concat (String str) - returns a string that consists of the string that it is operated on and in its end the string "str" is concatenated. Here is my try : public StringList concat (String str) { String str = ""; charNode pos = _head; if (str == null) return -1; for (pos = _head; pos!=null; pos = pos.getNext()) { str = str + pos.getData(); } str = str + "str"; return str; } Time complexity = O(N) Space complexity = O(1)

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• MySQL Syslog Audit Plugin

  - by jonathonc

  This post shows the construction process of the Syslog Audit plugin that was presented at MySQL Connect 2012. It is based on an environment that has the appropriate development tools enabled including gcc,g++ and cmake. It also assumes you have downloaded the MySQL source code (5.5.16 or higher) and have compiled and installed the system into the /usr/local/mysql directory ready for use.  The information provided below is designed to show the different components that make up a plugin, and specifically an audit type plugin, and how it comes together to be used within the MySQL service. The MySQL Reference Manual contains information regarding the plugin API and how it can be used, so please refer there for more detailed information. The code in this post is designed to give the simplest information necessary, so handling every return code, managing race conditions etc is not part of this example code. Let's start by looking at the most basic implementation of our plugin code as seen below: /*    Copyright (c) 2012, Oracle and/or its affiliates. All rights reserved.    Author:  Jonathon Coombes    Licence: GPL    Description: An auditing plugin that logs to syslog and                 can adjust the loglevel via the system variables. */ #include <stdio.h> #include <string.h> #include <mysql/plugin_audit.h> #include <syslog.h> There is a commented header detailing copyright/licencing and meta-data information and then the include headers. The two important include statements for our plugin are the syslog.h plugin, which gives us the structures for syslog, and the plugin_audit.h include which has details regarding the audit specific plugin api. Note that we do not need to include the general plugin header plugin.h, as this is done within the plugin_audit.h file already. To implement our plugin within the current implementation we need to add it into our source code and compile. > cd /usr/local/src/mysql-5.5.28/plugin > mkdir audit_syslog > cd audit_syslog A simple CMakeLists.txt file is created to manage the plugin compilation: MYSQL_ADD_PLUGIN(audit_syslog audit_syslog.cc MODULE_ONLY) Run the cmake  command at the top level of the source and then you can compile the plugin using the 'make' command. This results in a compiled audit_syslog.so library, but currently it is not much use to MySQL as there is no level of api defined to communicate with the MySQL service. Now we need to define the general plugin structure that enables MySQL to recognise the library as a plugin and be able to install/uninstall it and have it show up in the system. The structure is defined in the plugin.h file in the MySQL source code.  /*   Plugin library descriptor */ mysql_declare_plugin(audit_syslog) {   MYSQL_AUDIT_PLUGIN,           /* plugin type                    */   &audit_syslog_descriptor,     /* descriptor handle               */   "audit_syslog",               /* plugin name                     */   "Author Name",                /* author                          */   "Simple Syslog Audit",        /* description                     */   PLUGIN_LICENSE_GPL,           /* licence                         */   audit_syslog_init,            /* init function     */   audit_syslog_deinit,          /* deinit function */   0x0001,                       /* plugin version                  */   NULL,                         /* status variables        */   NULL,                         /* system variables                */   NULL,                         /* no reserves                     */   0,                            /* no flags                        */ } mysql_declare_plugin_end; The general plugin descriptor above is standard for all plugin types in MySQL. The plugin type is defined along with the init/deinit functions and interface methods into the system for sharing information, and various other metadata information. The descriptors have an internally recognised version number so that plugins can be matched against the api on the running server. The other details are usually related to the type-specific methods and structures to implement the plugin. Each plugin has a type-specific descriptor as well which details how the plugin is implemented for the specific purpose of that plugin type. /*   Plugin type-specific descriptor */ static struct st_mysql_audit audit_syslog_descriptor= {   MYSQL_AUDIT_INTERFACE_VERSION,                        /* interface version    */   NULL,                                                 /* release_thd function */   audit_syslog_notify,                                  /* notify function      */   { (unsigned long) MYSQL_AUDIT_GENERAL_CLASSMASK |                     MYSQL_AUDIT_CONNECTION_CLASSMASK }  /* class mask           */ }; In this particular case, the release_thd function has not been defined as it is not required. The important method for auditing is the notify function which is activated when an event occurs on the system. The notify function is designed to activate on an event and the implementation will determine how it is handled. For the audit_syslog plugin, the use of the syslog feature sends all events to the syslog for recording. The class mask allows us to determine what type of events are being seen by the notify function. There are currently two major types of event: 1. General Events: This includes general logging, errors, status and result type events. This is the main one for tracking the queries and operations on the database. 2. Connection Events: This group is based around user logins. It monitors connections and disconnections, but also if somebody changes user while connected. With most audit plugins, the principle behind the plugin is to track changes to the system over time and counters can be an important part of this process. The next step is to define and initialise the counters that are used to track the events in the service. There are 3 counters defined in total for our plugin - the # of general events, the # of connection events and the total number of events.  static volatile int total_number_of_calls; /* Count MYSQL_AUDIT_GENERAL_CLASS event instances */ static volatile int number_of_calls_general; /* Count MYSQL_AUDIT_CONNECTION_CLASS event instances */ static volatile int number_of_calls_connection; The init and deinit functions for the plugin are there to be called when the plugin is activated and when it is terminated. These offer the best option to initialise the counters for our plugin: /*  Initialize the plugin at server start or plugin installation. */ static int audit_syslog_init(void *arg __attribute__((unused))) {     openlog("mysql_audit:",LOG_PID|LOG_PERROR|LOG_CONS,LOG_USER);     total_number_of_calls= 0;     number_of_calls_general= 0;     number_of_calls_connection= 0;     return(0); } The init function does a call to openlog to initialise the syslog functionality. The parameters are the service to log under ("mysql_audit" in this case), the syslog flags and the facility for the logging. Then each of the counters are initialised to zero and a success is returned. If the init function is not defined, it will return success by default. /*  Terminate the plugin at server shutdown or plugin deinstallation. */ static int audit_syslog_deinit(void *arg __attribute__((unused))) {     closelog();     return(0); } The deinit function will simply close our syslog connection and return success. Note that the syslog functionality is part of the glibc libraries and does not require any external factors.  The function names are what we define in the general plugin structure, so these have to match otherwise there will be errors. The next step is to implement the event notifier function that was defined in the type specific descriptor (audit_syslog_descriptor) which is audit_syslog_notify. /* Event notifier function */ static void audit_syslog_notify(MYSQL_THD thd __attribute__((unused)), unsigned int event_class, const void *event) { total_number_of_calls++; if (event_class == MYSQL_AUDIT_GENERAL_CLASS) { const struct mysql_event_general *event_general= (const struct mysql_event_general *) event; number_of_calls_general++; syslog(audit_loglevel,"%lu: User: %s Command: %s Query: %s\n", event_general->general_thread_id, event_general->general_user, event_general->general_command, event_general->general_query ); } else if (event_class == MYSQL_AUDIT_CONNECTION_CLASS) { const struct mysql_event_connection *event_connection= (const struct mysql_event_connection *) event; number_of_calls_connection++; syslog(audit_loglevel,"%lu: User: %s@%s[%s] Event: %d Status: %d\n", event_connection->thread_id, event_connection->user, event_connection->host, event_connection->ip, event_connection->event_subclass, event_connection->status ); } }   In the case of an event, the notifier function is called. The first step is to increment the total number of events that have occurred in our database.The event argument is then cast into the appropriate event structure depending on the class type, of general event or connection event. The event type counters are incremented and details are sent via the syslog() function out to the system log. There are going to be different line formats and information returned since the general events have different data compared to the connection events, even though some of the details overlap, for example, user, thread id, host etc. On compiling the code now, there should be no errors and the resulting audit_syslog.so can be loaded into the server and ready to use. Log into the server and type: mysql> INSTALL PLUGIN audit_syslog SONAME 'audit_syslog.so'; This will install the plugin and will start updating the syslog immediately. Note that the audit plugin attaches to the immediate thread and cannot be uninstalled while that thread is active. This means that you cannot run the UNISTALL command until you log into a different connection (thread) on the server. Once the plugin is loaded, the system log will show output such as the following: Oct  8 15:33:21 machine mysql_audit:[8337]: 87: User: root[root] @ localhost []  Command: (null)  Query: INSTALL PLUGIN audit_syslog SONAME 'audit_syslog.so' Oct  8 15:33:21 machine mysql_audit:[8337]: 87: User: root[root] @ localhost []  Command: Query  Query: INSTALL PLUGIN audit_syslog SONAME 'audit_syslog.so' Oct  8 15:33:40 machine mysql_audit:[8337]: 87: User: root[root] @ localhost []  Command: (null)  Query: show tables Oct  8 15:33:40 machine mysql_audit:[8337]: 87: User: root[root] @ localhost []  Command: Query  Query: show tables Oct  8 15:33:43 machine mysql_audit:[8337]: 87: User: root[root] @ localhost []  Command: (null)  Query: select * from t1 Oct  8 15:33:43 machine mysql_audit:[8337]: 87: User: root[root] @ localhost []  Command: Query  Query: select * from t1 It appears that two of each event is being shown, but in actuality, these are two separate event types - the result event and the status event. This could be refined further by changing the audit_syslog_notify function to handle the different event sub-types in a different manner.  So far, it seems that the logging is working with events showing up in the syslog output. The issue now is that the counters created earlier to track the number of events by type are not accessible when the plugin is being run. Instead there needs to be a way to expose the plugin specific information to the service and vice versa. This could be done via the information_schema plugin api, but for something as simple as counters, the obvious choice is the system status variables. This is done using the standard structure and the declaration: /*  Plugin status variables for SHOW STATUS */ static struct st_mysql_show_var audit_syslog_status[]= {   { "Audit_syslog_total_calls",     (char *) &total_number_of_calls,     SHOW_INT },   { "Audit_syslog_general_events",     (char *) &number_of_calls_general,     SHOW_INT },   { "Audit_syslog_connection_events",     (char *) &number_of_calls_connection,     SHOW_INT },   { 0, 0, SHOW_INT } };   The structure is simply the name that will be displaying in the mysql service, the address of the associated variables, and the data type being used for the counter. It is finished with a blank structure to show that there are no more variables. Remember that status variables may have the same name for variables from other plugin, so it is considered appropriate to add the plugin name at the start of the status variable name to avoid confusion. Looking at the status variables in the mysql client shows something like the following: mysql> show global status like "audit%"; +--------------------------------+-------+ | Variable_name                  | Value | +--------------------------------+-------+ | Audit_syslog_connection_events | 1     | | Audit_syslog_general_events    | 2     | | Audit_syslog_total_calls       | 3     | +--------------------------------+-------+ 3 rows in set (0.00 sec) The final connectivity piece for the plugin is to allow the interactive change of the logging level between the plugin and the system. This requires the ability to send changes via the mysql service through to the plugin. This is done using the system variables interface and defining a single variable to keep track of the active logging level for the facility. /* Plugin system variables for SHOW VARIABLES */ static MYSQL_SYSVAR_STR(loglevel, audit_loglevel,                         PLUGIN_VAR_RQCMDARG,                         "User can specify the log level for auditing",                         audit_loglevel_check, audit_loglevel_update, "LOG_NOTICE"); static struct st_mysql_sys_var* audit_syslog_sysvars[] = {     MYSQL_SYSVAR(loglevel),     NULL }; So now the system variable 'loglevel' is defined for the plugin and associated to the global variable 'audit_loglevel'. The check or validation function is defined to make sure that no garbage values are attempted in the update of the variable. The update function is used to save the new value to the variable. Note that the audit_syslog_sysvars structure is defined in the general plugin descriptor to associate the link between the plugin and the system and how much they interact. Next comes the implementation of the validation function and the update function for the system variable. It is worth noting that if you have a simple numeric such as integers for the variable types, the validate function is often not required as MySQL will handle the automatic check and validation of simple types. /* longest valid value */ #define MAX_LOGLEVEL_SIZE 100 /* hold the valid values */ static const char *possible_modes[]= { "LOG_ERROR", "LOG_WARNING", "LOG_NOTICE", NULL };  static int audit_loglevel_check(     THD*                        thd,    /*!< in: thread handle */     struct st_mysql_sys_var*    var,    /*!< in: pointer to system                                         variable */     void*                       save,   /*!< out: immediate result                                         for update function */     struct st_mysql_value*      value)  /*!< in: incoming string */ {     char buff[MAX_LOGLEVEL_SIZE];     const char *str;     const char **found;     int length;     length= sizeof(buff);     if (!(str= value->val_str(value, buff, &length)))         return 1;     /*         We need to return a pointer to a locally allocated value in "save".         Here we pick to search for the supplied value in an global array of         constant strings and return a pointer to one of them.         The other possiblity is to use the thd_alloc() function to allocate         a thread local buffer instead of the global constants.     */     for (found= possible_modes; *found; found++)     {         if (!strcmp(*found, str))         {             *(const char**)save= *found;             return 0;         }     }     return 1; } The validation function is simply to take the value being passed in via the SET GLOBAL VARIABLE command and check if it is one of the pre-defined values allowed  in our possible_values array. If it is found to be valid, then the value is assigned to the save variable ready for passing through to the update function. static void audit_loglevel_update(     THD*                        thd,        /*!< in: thread handle */     struct st_mysql_sys_var*    var,        /*!< in: system variable                                             being altered */     void*                       var_ptr,    /*!< out: pointer to                                             dynamic variable */     const void*                 save)       /*!< in: pointer to                                             temporary storage */ {     /* assign the new value so that the server can read it */     *(char **) var_ptr= *(char **) save;     /* assign the new value to the internal variable */     audit_loglevel= *(char **) save; } Since all the validation has been done already, the update function is quite simple for this plugin. The first part is to update the system variable pointer so that the server can read the value. The second part is to update our own global plugin variable for tracking the value. Notice that the save variable is passed in as a void type to allow handling of various data types, so it must be cast to the appropriate data type when assigning it to the variables. Looking at how the latest changes affect the usage of the plugin and the interaction within the server shows: mysql> show global variables like "audit%"; +-----------------------+------------+ | Variable_name         | Value      | +-----------------------+------------+ | audit_syslog_loglevel | LOG_NOTICE | +-----------------------+------------+ 1 row in set (0.00 sec) mysql> set global audit_syslog_loglevel="LOG_ERROR"; Query OK, 0 rows affected (0.00 sec) mysql> show global status like "audit%"; +--------------------------------+-------+ | Variable_name                  | Value | +--------------------------------+-------+ | Audit_syslog_connection_events | 1     | | Audit_syslog_general_events    | 11    | | Audit_syslog_total_calls       | 12    | +--------------------------------+-------+ 3 rows in set (0.00 sec) mysql> show global variables like "audit%"; +-----------------------+-----------+ | Variable_name         | Value     | +-----------------------+-----------+ | audit_syslog_loglevel | LOG_ERROR | +-----------------------+-----------+ 1 row in set (0.00 sec)   So now we have a plugin that will audit the events on the system and log the details to the system log. It allows for interaction to see the number of different events within the server details and provides a mechanism to change the logging level interactively via the standard system methods of the SET command. A more complex auditing plugin may have more detailed code, but each of the above areas is what will be involved and simply expanded on to add more functionality. With the above skeleton code, it is now possible to create your own audit plugins to implement your own auditing requirements. If, however, you are not of the coding persuasion, then you could always consider the option of the MySQL Enterprise Audit plugin that is available to purchase.

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• Java: Cannot find a method's symbol even though that method is declared later in the class. The remaining code is looking for a class.

  - by Midimistro

  This is an assignment that we use strings in Java to analyze a phone number. The error I am having is anything below tester=invalidCharacters(c); does not compile because every line past tester=invalidCharacters(c); is looking for a symbol or the class. In get invalidResults, all I am trying to do is evaluate a given string for non-alphabetical characters such as *,(,^,&,%,@,#,), and so on. What to answer: Why is it producing an error, what will work, and is there an easier method WITHOUT using regex. Here is the link to the assignment: http://cis.csuohio.edu/~hwang/teaching/cis260/assignments/assignment9.html public class PhoneNumber { private int areacode; private int number; private int ext; /////Constructors///// //Third Constructor (given one string arg) "xxx-xxxxxxx" where first three are numbers and the remaining (7) are numbers or letters public PhoneNumber(String newNumber){ //Note: Set default ext to 0 ext=0; ////Declare Temporary Storage and other variables//// //for the first three numbers String areaCodeString; //for the remaining seven characters String newNumberString; //For use in testing the second half of the string boolean containsLetters; boolean containsInvalid; /////Separate the two parts of string///// //Get the area code part of the string areaCodeString=newNumber.substring(0,2); //Convert the string and set it to the area code areacode=Integer.parseInt(areaCodeString); //Skip the "-" and Get the remaining part of the string newNumberString=newNumber.substring(4); //Create an array of characters from newNumberString to reuse in later methods for int length=newNumberString.length(); char [] myCharacters= new char [length]; int i; for (i=0;i<length;i++){ myCharacters [i]=newNumberString.charAt(i); } //Test if newNumberString contains letters & converting them into numbers String reNewNumber=""; //Test for invalid characters containsInvalid=getInvalidResults(newNumberString,length); if (containsInvalid==false){ containsLetters=getCharResults(newNumberString,length); if (containsLetters==true){ for (i=0;i<length;i++){ myCharacters [i]=(char)convertLetNum((myCharacters [i])); reNewNumber=reNewNumber+myCharacters[i]; } } } if (containsInvalid==false){ number=Integer.parseInt(reNewNumber); } else{ System.out.println("Error!"+"\t"+newNumber+" contains illegal characters. This number will be ignored and skipped."); } } //////Primary Methods/Behaviors/////// //Compare this phone number with the one passed by the caller public boolean equals(PhoneNumber pn){ boolean equal; String concat=(areacode+"-"+number); String pN=pn.toString(); if (concat==pN){ equal=true; } else{ equal=false; } return equal; } //Convert the stored number to a certain string depending on extension public String toString(){ String returned; if(ext==0){ returned=(areacode+"-"+number); } else{ returned=(areacode+"-"+number+" ext "+ext); } return returned; } //////Secondary Methods/////// //Method for testing if the second part of the string contains any letters public static boolean getCharResults(String newNumString,int getLength){ //Recreate a character array int i; char [] myCharacters= new char [getLength]; for (i=0;i<getLength;i++){ myCharacters [i]=newNumString.charAt(i); } boolean doesContainLetter=false; int j; for (j=0;j<getLength;j++){ if ((Character.isDigit(myCharacters[j])==true)){ doesContainLetter=false; } else{ doesContainLetter=true; return doesContainLetter; } } return doesContainLetter; } //Method for testing if the second part of the string contains any letters public static boolean getInvalidResults(String newNumString,int getLength){ boolean doesContainInvalid=false; int i; char c; boolean tester; char [] invalidCharacters= new char [getLength]; for (i=0;i<getLength;i++){ invalidCharacters [i]=newNumString.charAt(i); c=invalidCharacters [i]; tester=invalidCharacters(c); if(tester==true)){ doesContainInvalid=false; } else{ doesContainInvalid=true; return doesContainInvalid; } } return doesContainInvalid; } //Method for evaluating string for invalid characters public boolean invalidCharacters(char letter){ boolean returnNum=false; switch (letter){ case 'A': return returnNum; case 'B': return returnNum; case 'C': return returnNum; case 'D': return returnNum; case 'E': return returnNum; case 'F': return returnNum; case 'G': return returnNum; case 'H': return returnNum; case 'I': return returnNum; case 'J': return returnNum; case 'K': return returnNum; case 'L': return returnNum; case 'M': return returnNum; case 'N': return returnNum; case 'O': return returnNum; case 'P': return returnNum; case 'Q': return returnNum; case 'R': return returnNum; case 'S': return returnNum; case 'T': return returnNum; case 'U': return returnNum; case 'V': return returnNum; case 'W': return returnNum; case 'X': return returnNum; case 'Y': return returnNum; case 'Z': return returnNum; default: return true; } } //Method for converting letters to numbers public int convertLetNum(char letter){ int returnNum; switch (letter){ case 'A': returnNum=2;return returnNum; case 'B': returnNum=2;return returnNum; case 'C': returnNum=2;return returnNum; case 'D': returnNum=3;return returnNum; case 'E': returnNum=3;return returnNum; case 'F': returnNum=3;return returnNum; case 'G': returnNum=4;return returnNum; case 'H': returnNum=4;return returnNum; case 'I': returnNum=4;return returnNum; case 'J': returnNum=5;return returnNum; case 'K': returnNum=5;return returnNum; case 'L': returnNum=5;return returnNum; case 'M': returnNum=6;return returnNum; case 'N': returnNum=6;return returnNum; case 'O': returnNum=6;return returnNum; case 'P': returnNum=7;return returnNum; case 'Q': returnNum=7;return returnNum; case 'R': returnNum=7;return returnNum; case 'S': returnNum=7;return returnNum; case 'T': returnNum=8;return returnNum; case 'U': returnNum=8;return returnNum; case 'V': returnNum=8;return returnNum; case 'W': returnNum=9;return returnNum; case 'X': returnNum=9;return returnNum; case 'Y': returnNum=9;return returnNum; case 'Z': returnNum=9;return returnNum; default: return 0; } } } Note: Please Do not use this program to cheat in your own class. To ensure of this, I will take this question down if it has not been answered by the end of 2013, if I no longer need an explanation for it, or if the term for the class has ended.

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• MySQL keeps crashing due to bug

  - by mike

  So about a week ago, I finally figured out what was causing my server to continually crash. After reviewing my mysqld.log I keep seeing this same error, 101210 5:04:32 [Warning] option 'max_join_size': unsigned value 18446744073709551615 adjusted to 4294967295 Here is a link to the bug report, http://bugs.mysql.com/bug.php?id=35346 someone recommend that you set the max_join_size vaule in my.cnf to 4M, and I did. I assumed this fixed the issue, and it was working for about a week with no issues until today... I checked MySQL and the same error is now back, 101216 06:35:25 mysqld restarted 101216 6:38:15 [Warning] option 'max_join_size': unsigned value 18446744073709551615 adjusted to 4294967295 101216 6:38:15 [Warning] option 'max_join_size': unsigned value 18446744073709551615 adjusted to 4294967295 101216 06:40:42 mysqld ended Anyone know how I can really fix this issue? I can't keep having mysql crash like this. EDIT: I forgot to mention every time this happens I get an email from linode staying I have a high disk io rate Your Linode, has exceeded the notification threshold (1000) for disk io rate by averaging 2483.68 for the last 2 hours.

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• AT91SAM7X512's SPI peripheral gets disabled on write to SPI_TDR

  - by Dor

  My AT91SAM7X512's SPI peripheral gets disabled on the X time (X varies) that I write to SPI_TDR. As a result, the processor hangs on the while loop that checks the TDRE flag in SPI_SR. This while loop is located in the function SPI_Write() that belongs to the software package/library provided by ATMEL. The problem occurs arbitrarily - sometimes everything works OK and sometimes it fails on repeated attempts (attemp = downloading the same binary to the MCU and running the program). Configurations are (defined in the order of writing): SPI_MR: MSTR = 1 PS = 0 PCSDEC = 0 PCS = 0111 DLYBCS = 0 SPI_CSR[3]: CPOL = 0 NCPHA = 1 CSAAT = 0 BITS = 0000 SCBR = 20 DLYBS = 0 DLYBCT = 0 SPI_CR: SPIEN = 1 After setting the configurations, the code verifies that the SPI is enabled, by checking the SPIENS flag. I perform a transmission of bytes as follows: const short int dataSize = 5; // Filling array with random data unsigned char data[dataSize] = {0xA5, 0x34, 0x12, 0x00, 0xFF}; short int i = 0; volatile unsigned short dummyRead; SetCS3(); // NPCS3 == PIOA15 while(i-- < dataSize) { mySPI_Write(data[i]); while((AT91C_BASE_SPI0->SPI_SR & AT91C_SPI_TXEMPTY) == 0); dummyRead = SPI_Read(); // SPI_Read() from Atmel's library } ClearCS3(); /**********************************/ void mySPI_Write(unsigned char data) { while ((AT91C_BASE_SPI0->SPI_SR & AT91C_SPI_TXEMPTY) == 0); AT91C_BASE_SPI0->SPI_TDR = data; while ((AT91C_BASE_SPI0->SPI_SR & AT91C_SPI_TDRE) == 0); // <-- This is where // the processor hangs, because that the SPI peripheral is disabled // (SPIENS equals 0), which makes TDRE equal to 0 forever. } Questions: What's causing the SPI peripheral to become disabled on the write to SPI_TDR? Should I un-comment the line in SPI_Write() that reads the SPI_RDR register? Means, the 4th line in the following code: (The 4th line is originally marked as a comment) void SPI_Write(AT91S_SPI *spi, unsigned int npcs, unsigned short data) { // Discard contents of RDR register //volatile unsigned int discard = spi->SPI_RDR; /* Send data */ while ((spi->SPI_SR & AT91C_SPI_TXEMPTY) == 0); spi->SPI_TDR = data | SPI_PCS(npcs); while ((spi->SPI_SR & AT91C_SPI_TDRE) == 0); } Is there something wrong with the code above that transmits 5 bytes of data? Please note: The NPCS line num. 3 is a GPIO line (means, in PIO mode), and is not controlled by the SPI controller. I'm controlling this line by myself in the code, by de/asserting the ChipSelect#3 (NPCS3) pin when needed. The reason that I'm doing so is because that problems occurred while trying to let the SPI controller to control this pin. I didn't reset the SPI peripheral twice, because that the errata tells to reset it twice only if I perform a reset - which I don't do. Quoting the errata: If a software reset (SWRST in the SPI Control Register) is performed, the SPI may not work properly (the clock is enabled before the chip select.) Problem Fix/Workaround The SPI Control Register field, SWRST (Software Reset) needs to be written twice to be cor- rectly set. I noticed that sometimes, if I put a delay before the write to the SPI_TDR register (in SPI_Write()), then the code works perfectly and the communications succeeds. Useful links: AT91SAM7X Series Preliminary.pdf ATMEL software package/library spi.c from Atmel's library spi.h from Atmel's library An example of initializing the SPI and performing a transfer of 5 bytes is highly appreciated and helpful.

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• Weird order when painting triangle outlines using GL_LINE_STRIP

  - by RayDeeA

  I'm developing an app for iOS-Plaftorms using OpenGL. Currently I'm having a weird issue when painting a plane (terrain) which consists of multiple subplanes, where each subplane consists of 2 triangles forming a rect. I'm painting this terrain as a wireframe by using a call to glDrawElements and provide the parameters GL_Line_Strip and the precalculated indices. The problem is that the triangles get painted in the wrong order or are rather vertically mirrored. They do not get painted in the order how I specified the indices, which is confusing. This is the simplified code to generate the vertices: for(NSInteger y = - gridSegmentsY / 2; y < gridSegmentsY / 2; y ++) { for(NSInteger x = - gridSegmentsX / 2; x < gridSegmentsX / 2; x ++) { vertices[pos++] = x * 5; vertices[pos++] = y * 5; vertices[pos++] = 0; } } This is how I generate the indices including degenerated ones (To use as IBO). pos = 0; for(int y = 0; y < gridSegmentsY - 1; y ++) { if (y > 0) { // Degenerate begin: repeat first vertex indices[pos++] = (unsigned short)(y * gridSegmentsY); } for(int x = 0; x < gridSegmentsX; x++) { // One part of the strip indices[pos++] = (unsigned short)((y * gridSegmentsY) + x); indices[pos++] = (unsigned short)(((y + 1) * gridSegmentsY) + x); } if (y < gridSegmentsY - 2) { // Degenerate end: repeat last vertex indices[pos++] = (unsigned short)(((y + 1) * gridSegmentsY) + (gridSegmentsX - 1)); } } So in this part... indices[pos++] = (unsigned short)((y * gridSegmentsY) + x); indices[pos++] = (unsigned short)(((y + 1) * gridSegmentsY) + x); ...I'm setting the first index in the indices array to point to the current (x,y) and the next index to (x,y+1). I'm doin' this for all x's in the current strip, then I'm handling degenerated triangles and repeat this procedure for the next strip (y+1). This method is taken from http://www.learnopengles.com/android-lesson-eight-an-introduction-to-index-buffer-objects-ibos/ So I expect the resulting mesh to get painted like: a----b----c | /| /| | / | / | | / | / | |/ |/ | d----e----f | /| /| | / | / | | / | / | |/ |/ | g----h----i by painting it as described using: glDrawElements(GL_LINE_STRIP, indexCount, GL_UNSIGNED_SHORT, 0); ...since I expect GL_Line_Strip to paint first a line from (a-d), then from (d-b), then (b, e)... and so on (as specified in the indices calculation) But what actually gets painted is: *----*----* |\ |\ | | \ | \ | | \ | \ | | \| \| *----*----* |\ |\ | | \ | \ | | \ | \ | | \| \| *----*----* So the triangles are somehow painted in the wrong order and I need to know why? ;). Does somebody know? Does the problem lie in using GL_Line_Strip or is there a bug in my code? My eye is at (0.0f, 0.0f, 20.0f) and looks at (0,0,0). The mesh is painted along the x-axis & y-axis from left to right with z = 0, so the mesh should not be flipped or anything.

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• java inserting special characters with preparedstatement fails

  - by phill

  I am using an HTML form which sends <input type=hidden name=longdesc value='SMARTNET%^" 8X5XNBD'> this is done by the following javascript code: function masinsert(id) { var currentTime=new Date(); var button = document.getElementById("m"+id); button.onclick=""; button.value="Inserting"; var itemdescription = document.getElementById("itemdescription"+id).value; function handleHttpResponse() { if (http.readyState == 4) { button.value="Item Added"; } } var http = getHTTPObject(); // We create the HTTP Object var tempUrl = "\AInsert"; tempUrl += "itemdescription="+itemdescription+"&"+"itemshortdescription="+itemdescription.substring(0,37)+; alert(tempUrl); http.open("GET", tempUrl, true); http.onreadystatechange = handleHttpResponse; http.send(null); } to a java servlet. AInsert.java in the AInsert.java file, I do a String itemdescription = request.getParameter("longdesc"); which then sends the value to a preparedstatement to run an insert query. In the query, there are sometimes special characters which throw it off. For example, when I run the following insert into itemdescription (longdesc) values ('SMARTNET%^" 8X5XNBD') here is the actual snippet: PreparedStatement ps = conn.prepareStatement("INSERT INTO itemdescription (longdesc) values(?)"); ps.setString(1, itemdescription); ps.executeUpdate(); It will produce an error saying : Cannot insert the value NULL into column 'LongDesc', table 'App.dbo.itemdescription'; column does not allow nulls. Insert fails I have tried urlencode/urldecode String encodedString = URLEncoder.encode(longdesc, "UTF-8"); String decitemdescription = URLDecoder.decode(itemdescription, "UTF-8"); and i've also tried these functions //BEGIN URL Encoder final static String[] hex = { "%00", "%01", "%02", "%03", "%04", "%05", "%06", "%07", "%08", "%09", "%0a", "%0b", "%0c", "%0d", "%0e", "%0f", "%10", "%11", "%12", "%13", "%14", "%15", "%16", "%17", "%18", "%19", "%1a", "%1b", "%1c", "%1d", "%1e", "%1f", "%20", "%21", "%22", "%23", "%24", "%25", "%26", "%27", "%28", "%29", "%2a", "%2b", "%2c", "%2d", "%2e", "%2f", "%30", "%31", "%32", "%33", "%34", "%35", "%36", "%37", "%38", "%39", "%3a", "%3b", "%3c", "%3d", "%3e", "%3f", "%40", "%41", "%42", "%43", "%44", "%45", "%46", "%47", "%48", "%49", "%4a", "%4b", "%4c", "%4d", "%4e", "%4f", "%50", "%51", "%52", "%53", "%54", "%55", "%56", "%57", "%58", "%59", "%5a", "%5b", "%5c", "%5d", "%5e", "%5f", "%60", "%61", "%62", "%63", "%64", "%65", "%66", "%67", "%68", "%69", "%6a", "%6b", "%6c", "%6d", "%6e", "%6f", "%70", "%71", "%72", "%73", "%74", "%75", "%76", "%77", "%78", "%79", "%7a", "%7b", "%7c", "%7d", "%7e", "%7f", "%80", "%81", "%82", "%83", "%84", "%85", "%86", "%87", "%88", "%89", "%8a", "%8b", "%8c", "%8d", "%8e", "%8f", "%90", "%91", "%92", "%93", "%94", "%95", "%96", "%97", "%98", "%99", "%9a", "%9b", "%9c", "%9d", "%9e", "%9f", "%a0", "%a1", "%a2", "%a3", "%a4", "%a5", "%a6", "%a7", "%a8", "%a9", "%aa", "%ab", "%ac", "%ad", "%ae", "%af", "%b0", "%b1", "%b2", "%b3", "%b4", "%b5", "%b6", "%b7", "%b8", "%b9", "%ba", "%bb", "%bc", "%bd", "%be", "%bf", "%c0", "%c1", "%c2", "%c3", "%c4", "%c5", "%c6", "%c7", "%c8", "%c9", "%ca", "%cb", "%cc", "%cd", "%ce", "%cf", "%d0", "%d1", "%d2", "%d3", "%d4", "%d5", "%d6", "%d7", "%d8", "%d9", "%da", "%db", "%dc", "%dd", "%de", "%df", "%e0", "%e1", "%e2", "%e3", "%e4", "%e5", "%e6", "%e7", "%e8", "%e9", "%ea", "%eb", "%ec", "%ed", "%ee", "%ef", "%f0", "%f1", "%f2", "%f3", "%f4", "%f5", "%f6", "%f7", "%f8", "%f9", "%fa", "%fb", "%fc", "%fd", "%fe", "%ff" }; /** * Encode a string to the "x-www-form-urlencoded" form, enhanced * with the UTF-8-in-URL proposal. This is what happens: * * <ul> * <li><p>The ASCII characters 'a' through 'z', 'A' through 'Z', * and '0' through '9' remain the same. * * <li><p>The unreserved characters - _ . ! ~ * ' ( ) remain the same. * * <li><p>The space character ' ' is converted into a plus sign '+'. * * <li><p>All other ASCII characters are converted into the * 3-character string "%xy", where xy is * the two-digit hexadecimal representation of the character * code * * <li><p>All non-ASCII characters are encoded in two steps: first * to a sequence of 2 or 3 bytes, using the UTF-8 algorithm; * secondly each of these bytes is encoded as "%xx". * </ul> * * @param s The string to be encoded * @return The encoded string */ public static String encode(String s) { StringBuffer sbuf = new StringBuffer(); int len = s.length(); for (int i = 0; i < len; i++) { int ch = s.charAt(i); if ('A' <= ch && ch <= 'Z') { // 'A'..'Z' sbuf.append((char)ch); } else if ('a' <= ch && ch <= 'z') { // 'a'..'z' sbuf.append((char)ch); } else if ('0' <= ch && ch <= '9') { // '0'..'9' sbuf.append((char)ch); } else if (ch == ' ') { // space sbuf.append('+'); } else if (ch == '-' || ch == '_' // unreserved || ch == '.' || ch == '!' || ch == '~' || ch == '*' || ch == '\'' || ch == '(' || ch == ')') { sbuf.append((char)ch); } else if (ch <= 0x007f) { // other ASCII sbuf.append(hex[ch]); } else if (ch <= 0x07FF) { // non-ASCII <= 0x7FF sbuf.append(hex[0xc0 | (ch >> 6)]); sbuf.append(hex[0x80 | (ch & 0x3F)]); } else { // 0x7FF < ch <= 0xFFFF sbuf.append(hex[0xe0 | (ch >> 12)]); sbuf.append(hex[0x80 | ((ch >> 6) & 0x3F)]); sbuf.append(hex[0x80 | (ch & 0x3F)]); } } return sbuf.toString(); } //end encode and //decode url private static String unescape(String s) { StringBuffer sbuf = new StringBuffer () ; int l = s.length() ; int ch = -1 ; int b, sumb = 0; for (int i = 0, more = -1 ; i < l ; i++) { /* Get next byte b from URL segment s */ switch (ch = s.charAt(i)) { case '%': ch = s.charAt (++i) ; int hb = (Character.isDigit ((char) ch) ? ch - '0' : 10+Character.toLowerCase((char) ch) - 'a') & 0xF ; ch = s.charAt (++i) ; int lb = (Character.isDigit ((char) ch) ? ch - '0' : 10+Character.toLowerCase ((char) ch)-'a') & 0xF ; b = (hb << 4) | lb ; break ; case '+': b = ' ' ; break ; default: b = ch ; } /* Decode byte b as UTF-8, sumb collects incomplete chars */ if ((b & 0xc0) == 0x80) { // 10xxxxxx (continuation byte) sumb = (sumb << 6) | (b & 0x3f) ; // Add 6 bits to sumb if (--more == 0) sbuf.append((char) sumb) ; // Add char to sbuf } else if ((b & 0x80) == 0x00) { // 0xxxxxxx (yields 7 bits) sbuf.append((char) b) ; // Store in sbuf } else if ((b & 0xe0) == 0xc0) { // 110xxxxx (yields 5 bits) sumb = b & 0x1f; more = 1; // Expect 1 more byte } else if ((b & 0xf0) == 0xe0) { // 1110xxxx (yields 4 bits) sumb = b & 0x0f; more = 2; // Expect 2 more bytes } else if ((b & 0xf8) == 0xf0) { // 11110xxx (yields 3 bits) sumb = b & 0x07; more = 3; // Expect 3 more bytes } else if ((b & 0xfc) == 0xf8) { // 111110xx (yields 2 bits) sumb = b & 0x03; more = 4; // Expect 4 more bytes } else /*if ((b & 0xfe) == 0xfc)*/ { // 1111110x (yields 1 bit) sumb = b & 0x01; more = 5; // Expect 5 more bytes } /* We don't test if the UTF-8 encoding is well-formed */ } return sbuf.toString() ; } but the decoding doesn't change it back to the original special characters. Any ideas? thanks in advance UPDATE: I tried adding these two statements to grab the request String itemdescription = URLDecoder.decode(request.getParameter("itemdescription"), "UTF-8"); String itemshortdescription = URLDecoder.decode(request.getParameter("itemshortdescription"), "UTF-8"); System.out.println("processRequest | short descrip "); and this is failing as well if that helps. UPDATE2: I created an html form and did a direct insert with the encoded itemdescription such as and the insertion works correctly with the special charaters and everything. I guess there is something going on with my javascript submit. Any ideas on this?

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• Overloading stream insertion without violating information hiding?

  - by Chris

  I'm using yaml-cpp for a project. I want to overload the << and >> operators for some classes, but I'm having an issue grappling with how to "properly" do this. Take the Note class, for example. It's fairly boring: class Note { public: // constructors Note( void ); ~Note( void ); // public accessor methods void number( const unsigned long& number ) { _number = number; } unsigned long number( void ) const { return _number; } void author( const unsigned long& author ) { _author = author; } unsigned long author( void ) const { return _author; } void subject( const std::string& subject ) { _subject = subject; } std::string subject( void ) const { return _subject; } void body( const std::string& body ) { _body = body; } std::string body( void ) const { return _body; } private: unsigned long _number; unsigned long _author; std::string _subject; std::string _body; }; The << operator is easy sauce. In the .h: YAML::Emitter& operator << ( YAML::Emitter& out, const Note& v ); And in the .cpp: YAML::Emitter& operator << ( YAML::Emitter& out, const Note& v ) { out << v.number() << v.author() << v.subject() << v.body(); return out; } No sweat. Then I go to declare the >> operator. In the .h: void operator >> ( const YAML::Node& node, Note& note ); But in the .cpp I get: void operator >> ( const YAML::Node& node, Note& note ) { node[0] >> ? node[1] >> ? node[2] >> ? node[3] >> ? return; } If I write things like node[0] >> v._number; then I would need to change the CV-qualifier to make all of the Note fields public (which defeats everything I was taught (by professors, books, and experience))) about data hiding. I feel like doing node[0] >> temp0; v.number( temp0 ); all over the place is not only tedious, error-prone, and ugly, but rather wasteful (what with the extra copies). Then I got wise: I attempted to move these two operators into the Note class itself, and declare them as friends, but the compiler (GCC 4.4) didn't like that: src/note.h:44: error: ‘YAML::Emitter& Note::operator<<(YAML::Emitter&, const Note&)’ must take exactly one argument src/note.h:45: error: ‘void Note::operator(const YAML::Node&, Note&)’ must take exactly one argument Question: How do I "properly" overload the >> operator for a class Without violating the information hiding principle? Without excessive copying?

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• Insert a transformed integer_sequence into a variadic template argument?

  - by coderforlife

  How do you insert a transformed integer_sequence (or similar since I am targeting C++11) into a variadic template argument? For example I have a class that represents a set of bit-wise flags (shown below). It is made using a nested-class because you cannot have two variadic template arguments for the same class. It would be used like typedef Flags<unsigned char, FLAG_A, FLAG_B, FLAG_C>::WithValues<0x01, 0x02, 0x04> MyFlags. Typically, they will be used with the values that are powers of two (although not always, in some cases certain combinations would be made, for example one could imagine a set of flags like Read=0x1, Write=0x2, and ReadWrite=0x3=0x1|0x2). I would like to provide a way to do typedef Flags<unsigned char, FLAG_A, FLAG_B, FLAG_C>::WithDefaultValues MyFlags. template<class _B, template <class,class,_B> class... _Fs> class Flags { public: template<_B... _Vs> class WithValues : public _Fs<_B, Flags<_B,_Fs...>::WithValues<_Vs...>, _Vs>... { // ... }; }; I have tried the following without success (placed inside the Flags class, outside the WithValues class): private: struct _F { // dummy class which can be given to a flag-name template template <_B _V> inline constexpr explicit _F(std::integral_constant<_B, _V>) { } }; // we count the flags, but only in a dummy way static constexpr unsigned _count = sizeof...(_Fs<_B, _F, 1>); static inline constexpr _B pow2(unsigned exp, _B base = 2, _B result = 1) { return exp < 1 ? result : pow2(exp/2, base*base, (exp % 2) ? result*base : result); } template <_B... _Is> struct indices { using next = indices<_Is..., sizeof...(_Is)>; using WithPow2Values = WithValues<pow2(_Is)...>; }; template <unsigned N> struct build_indices { using type = typename build_indices<N-1>::type::next; }; template <> struct build_indices<0> { using type = indices<>; }; //// Another attempt //template < _B... _Is> struct indices { // using WithPow2Values = WithValues<pow2(_Is)...>; //}; //template <unsigned N, _B... _Is> struct build_indices // : build_indices<N-1, N-1, _Is...> { }; //template < _B... _Is> struct build_indices<0, _Is...> // : indices<_Is...> { }; public: using WithDefaultValues = typename build_indices<_count>::type::WithPow2Values; Of course, I would be willing to have any other alternatives to the whole situation (supporting both flag names and values in the same template set, etc). I have included a "working" example at ideone: http://ideone.com/NYtUrg - by "working" I mean compiles fine without using default values but fails with default values (there is a #define to switch between them). Thanks!

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• Strange mesh import problem with Assimp and OpenGL

  - by Morgan

  Using the assimp library for importing 3D data into an OpenGL application. I get some strange problems regarding indexing of the vertices: If I use the following code for importing vertex indices: for (unsigned int t = 0; t < mesh->mNumFaces; ++t) { const struct aiFace * face = &mesh->mFaces[t]; if (face->mNumIndices == 3) { indices->push_back(face->mIndices[0]); indices->push_back(face->mIndices[1]); indices->push_back(face->mIndices[2]); } } I get the following result: Instead, if I use the following code: for(int k = 0; k < 2 ; k++) { for (unsigned int t = 0; t < mesh->mNumFaces; ++t) { const struct aiFace * face = &mesh->mFaces[t]; if (face->mNumIndices == 3) { indices->push_back(face->mIndices[0]); indices->push_back(face->mIndices[1]); indices->push_back(face->mIndices[2]); } } } I get the correct result: Hence adding the indices twice, renders the correct result? The OpenGL buffer is populated, like so: glBufferData(GL_ELEMENT_ARRAY_BUFFER, indices->size() * sizeof(unsigned int), indices->data(), GL_STATIC_DRAW); And rendered as follows: glDrawElements(GL_TRIANGLES, vertexCount*3, GL_UNSIGNED_INT, indices->data());

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• Steering evaluate fitness

  - by Vodemki

  I've made a simple game with a steering model that manage a crowd of agents. I use an genetic algorithm to find the best parameters to use in my system but I need to determine a fitness for each simulation. I know it's something like that: number of collisions * time to reach goal * effort But I don't know how to calculate the effort, is there a special way to do that ? Here is what I've done so far: // Evaluate the distance from agents to goal Real totalDistance(0.0); for (unsigned i=0; i<_agents.size(); i++) { totalDistance += _agents[i]->position().distance(_agents[i]->_goal->position()); } Real totalWallsCollision(0.0); for (unsigned i=0; i<_agents.size(); i++) { for (unsigned j=0; j<walls.size(); j++) { if ( walls[j]->inside(_agents[i]->position()) ) { totalCollision += 1.0; } } } return totalDistance + totalWallsCollision; Thanks for your help.

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• Hook IDispatch v-table in C++

  - by monoceres

  I'm trying to modify the behavior of an IDispatch interface already present in the system. To do this my plan was to hook into the objects v-table during runtime and modify the pointers so it points to a custom hook method instead. If I can get this to work I can add new methods and properties to already existing objects. Nice. First I tried hooking into the v-table for IUnknown (from which IDispatch inherits from) and that worked fine. However trying to change entires in IDispatch doesn't work at all. Nothing happens at all, the code works just as it did without the hook. Here's the code, it's very simple so it shouldn't be any problems to understand #include <iostream> #include <windows.h> #include <Objbase.h> #pragma comment (lib,"Ole32.lib") using namespace std; HRESULT __stdcall typecount(IDispatch *self,UINT*u) { cout << "hook" << endl; *u=1; return S_OK; } int main() { CoInitialize(NULL); // Get clsid from name CLSID clsid; CLSIDFromProgID(L"shell.application",&clsid); // Create instance IDispatch *obj=NULL; CoCreateInstance(clsid,NULL,CLSCTX_INPROC_SERVER,__uuidof(IDispatch),(void**)&obj); // Get vtable and offset in vtable for idispatch void* iunknown_vtable= (void*)*((unsigned int*)obj); // There are three entries in IUnknown, therefore add 12 to go to IDispatch void* idispatch_vtable = (void*)(((unsigned int)iunknown_vtable)+12); // Get pointer of first emtry in IDispatch vtable (GetTypeInfoCount) unsigned int* v1 = (unsigned int*)iunknown_vtable; // Change memory permissions so address can be overwritten DWORD old; VirtualProtect(v1,4,PAGE_EXECUTE_READWRITE,&old); // Override v-table pointer *v1 = (unsigned int) typecount; // Try calling GetTypeInfo count, should now be hooked. But isn't works as usual UINT num=0; obj->GetTypeInfoCount(&num); /* HRESULT hresult; OLECHAR FAR* szMember = (OLECHAR*)L"MinimizeAll"; DISPID dispid; DISPPARAMS dispparamsNoArgs = {NULL, NULL, 0, 0}; hresult = obj->GetIDsOfNames(IID_NULL, &szMember, 1, LOCALE_SYSTEM_DEFAULT, &dispid) ; hresult = obj->Invoke(dispid,IID_NULL,LOCALE_SYSTEM_DEFAULT,DISPATCH_METHOD,&dispparamsNoArgs, NULL, NULL, NULL); */ } Thanks in advance!

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• Advanced TSQL Tuning: Why Internals Knowledge Matters

  - by Paul White

  There is much more to query tuning than reducing logical reads and adding covering nonclustered indexes.  Query tuning is not complete as soon as the query returns results quickly in the development or test environments.  In production, your query will compete for memory, CPU, locks, I/O and other resources on the server.  Today’s entry looks at some tuning considerations that are often overlooked, and shows how deep internals knowledge can help you write better TSQL. As always, we’ll need some example data.  In fact, we are going to use three tables today, each of which is structured like this: Each table has 50,000 rows made up of an INTEGER id column and a padding column containing 3,999 characters in every row.  The only difference between the three tables is in the type of the padding column: the first table uses CHAR(3999), the second uses VARCHAR(MAX), and the third uses the deprecated TEXT type.  A script to create a database with the three tables and load the sample data follows: USE master; GO IF DB_ID('SortTest') IS NOT NULL DROP DATABASE SortTest; GO CREATE DATABASE SortTest COLLATE LATIN1_GENERAL_BIN; GO ALTER DATABASE SortTest MODIFY FILE ( NAME = 'SortTest', SIZE = 3GB, MAXSIZE = 3GB ); GO ALTER DATABASE SortTest MODIFY FILE ( NAME = 'SortTest_log', SIZE = 256MB, MAXSIZE = 1GB, FILEGROWTH = 128MB ); GO ALTER DATABASE SortTest SET ALLOW_SNAPSHOT_ISOLATION OFF ; ALTER DATABASE SortTest SET AUTO_CLOSE OFF ; ALTER DATABASE SortTest SET AUTO_CREATE_STATISTICS ON ; ALTER DATABASE SortTest SET AUTO_SHRINK OFF ; ALTER DATABASE SortTest SET AUTO_UPDATE_STATISTICS ON ; ALTER DATABASE SortTest SET AUTO_UPDATE_STATISTICS_ASYNC ON ; ALTER DATABASE SortTest SET PARAMETERIZATION SIMPLE ; ALTER DATABASE SortTest SET READ_COMMITTED_SNAPSHOT OFF ; ALTER DATABASE SortTest SET MULTI_USER ; ALTER DATABASE SortTest SET RECOVERY SIMPLE ; USE SortTest; GO CREATE TABLE dbo.TestCHAR ( id INTEGER IDENTITY (1,1) NOT NULL, padding CHAR(3999) NOT NULL,   CONSTRAINT [PK dbo.TestCHAR (id)] PRIMARY KEY CLUSTERED (id), ) ; CREATE TABLE dbo.TestMAX ( id INTEGER IDENTITY (1,1) NOT NULL, padding VARCHAR(MAX) NOT NULL,   CONSTRAINT [PK dbo.TestMAX (id)] PRIMARY KEY CLUSTERED (id), ) ; CREATE TABLE dbo.TestTEXT ( id INTEGER IDENTITY (1,1) NOT NULL, padding TEXT NOT NULL,   CONSTRAINT [PK dbo.TestTEXT (id)] PRIMARY KEY CLUSTERED (id), ) ; -- ============= -- Load TestCHAR (about 3s) -- ============= INSERT INTO dbo.TestCHAR WITH (TABLOCKX) ( padding ) SELECT padding = REPLICATE(CHAR(65 + (Data.n % 26)), 3999) FROM ( SELECT TOP (50000) n = ROW_NUMBER() OVER (ORDER BY (SELECT 0)) - 1 FROM master.sys.columns C1, master.sys.columns C2, master.sys.columns C3 ORDER BY n ASC ) AS Data ORDER BY Data.n ASC ; -- ============ -- Load TestMAX (about 3s) -- ============ INSERT INTO dbo.TestMAX WITH (TABLOCKX) ( padding ) SELECT CONVERT(VARCHAR(MAX), padding) FROM dbo.TestCHAR ORDER BY id ; -- ============= -- Load TestTEXT (about 5s) -- ============= INSERT INTO dbo.TestTEXT WITH (TABLOCKX) ( padding ) SELECT CONVERT(TEXT, padding) FROM dbo.TestCHAR ORDER BY id ; -- ========== -- Space used -- ========== -- EXECUTE sys.sp_spaceused @objname = 'dbo.TestCHAR'; EXECUTE sys.sp_spaceused @objname = 'dbo.TestMAX'; EXECUTE sys.sp_spaceused @objname = 'dbo.TestTEXT'; ; CHECKPOINT ; That takes around 15 seconds to run, and shows the space allocated to each table in its output: To illustrate the points I want to make today, the example task we are going to set ourselves is to return a random set of 150 rows from each table.  The basic shape of the test query is the same for each of the three test tables: SELECT TOP (150) T.id, T.padding FROM dbo.Test AS T ORDER BY NEWID() OPTION (MAXDOP 1) ; Test 1 – CHAR(3999) Running the template query shown above using the TestCHAR table as the target, we find that the query takes around 5 seconds to return its results.  This seems slow, considering that the table only has 50,000 rows.  Working on the assumption that generating a GUID for each row is a CPU-intensive operation, we might try enabling parallelism to see if that speeds up the response time.  Running the query again (but without the MAXDOP 1 hint) on a machine with eight logical processors, the query now takes 10 seconds to execute – twice as long as when run serially. Rather than attempting further guesses at the cause of the slowness, let’s go back to serial execution and add some monitoring.  The script below monitors STATISTICS IO output and the amount of tempdb used by the test query.  We will also run a Profiler trace to capture any warnings generated during query execution. DECLARE @read BIGINT, @write BIGINT ; SELECT @read = SUM(num_of_bytes_read), @write = SUM(num_of_bytes_written) FROM tempdb.sys.database_files AS DBF JOIN sys.dm_io_virtual_file_stats(2, NULL) AS FS ON FS.file_id = DBF.file_id WHERE DBF.type_desc = 'ROWS' ; SET STATISTICS IO ON ; SELECT TOP (150) TC.id, TC.padding FROM dbo.TestCHAR AS TC ORDER BY NEWID() OPTION (MAXDOP 1) ; SET STATISTICS IO OFF ; SELECT tempdb_read_MB = (SUM(num_of_bytes_read) - @read) / 1024. / 1024., tempdb_write_MB = (SUM(num_of_bytes_written) - @write) / 1024. / 1024., internal_use_MB = ( SELECT internal_objects_alloc_page_count / 128.0 FROM sys.dm_db_task_space_usage WHERE session_id = @@SPID ) FROM tempdb.sys.database_files AS DBF JOIN sys.dm_io_virtual_file_stats(2, NULL) AS FS ON FS.file_id = DBF.file_id WHERE DBF.type_desc = 'ROWS' ; Let’s take a closer look at the statistics and query plan generated from this: Following the flow of the data from right to left, we see the expected 50,000 rows emerging from the Clustered Index Scan, with a total estimated size of around 191MB.  The Compute Scalar adds a column containing a random GUID (generated from the NEWID() function call) for each row.  With this extra column in place, the size of the data arriving at the Sort operator is estimated to be 192MB. Sort is a blocking operator – it has to examine all of the rows on its input before it can produce its first row of output (the last row received might sort first).  This characteristic means that Sort requires a memory grant – memory allocated for the query’s use by SQL Server just before execution starts.  In this case, the Sort is the only memory-consuming operator in the plan, so it has access to the full 243MB (248,696KB) of memory reserved by SQL Server for this query execution. Notice that the memory grant is significantly larger than the expected size of the data to be sorted.  SQL Server uses a number of techniques to speed up sorting, some of which sacrifice size for comparison speed.  Sorts typically require a very large number of comparisons, so this is usually a very effective optimization.  One of the drawbacks is that it is not possible to exactly predict the sort space needed, as it depends on the data itself.  SQL Server takes an educated guess based on data types, sizes, and the number of rows expected, but the algorithm is not perfect. In spite of the large memory grant, the Profiler trace shows a Sort Warning event (indicating that the sort ran out of memory), and the tempdb usage monitor shows that 195MB of tempdb space was used – all of that for system use.  The 195MB represents physical write activity on tempdb, because SQL Server strictly enforces memory grants – a query cannot ‘cheat’ and effectively gain extra memory by spilling to tempdb pages that reside in memory.  Anyway, the key point here is that it takes a while to write 195MB to disk, and this is the main reason that the query takes 5 seconds overall. If you are wondering why using parallelism made the problem worse, consider that eight threads of execution result in eight concurrent partial sorts, each receiving one eighth of the memory grant.  The eight sorts all spilled to tempdb, resulting in inefficiencies as the spilled sorts competed for disk resources.  More importantly, there are specific problems at the point where the eight partial results are combined, but I’ll cover that in a future post. CHAR(3999) Performance Summary: 5 seconds elapsed time 243MB memory grant 195MB tempdb usage 192MB estimated sort set 25,043 logical reads Sort Warning Test 2 – VARCHAR(MAX) We’ll now run exactly the same test (with the additional monitoring) on the table using a VARCHAR(MAX) padding column: DECLARE @read BIGINT, @write BIGINT ; SELECT @read = SUM(num_of_bytes_read), @write = SUM(num_of_bytes_written) FROM tempdb.sys.database_files AS DBF JOIN sys.dm_io_virtual_file_stats(2, NULL) AS FS ON FS.file_id = DBF.file_id WHERE DBF.type_desc = 'ROWS' ; SET STATISTICS IO ON ; SELECT TOP (150) TM.id, TM.padding FROM dbo.TestMAX AS TM ORDER BY NEWID() OPTION (MAXDOP 1) ; SET STATISTICS IO OFF ; SELECT tempdb_read_MB = (SUM(num_of_bytes_read) - @read) / 1024. / 1024., tempdb_write_MB = (SUM(num_of_bytes_written) - @write) / 1024. / 1024., internal_use_MB = ( SELECT internal_objects_alloc_page_count / 128.0 FROM sys.dm_db_task_space_usage WHERE session_id = @@SPID ) FROM tempdb.sys.database_files AS DBF JOIN sys.dm_io_virtual_file_stats(2, NULL) AS FS ON FS.file_id = DBF.file_id WHERE DBF.type_desc = 'ROWS' ; This time the query takes around 8 seconds to complete (3 seconds longer than Test 1).  Notice that the estimated row and data sizes are very slightly larger, and the overall memory grant has also increased very slightly to 245MB.  The most marked difference is in the amount of tempdb space used – this query wrote almost 391MB of sort run data to the physical tempdb file.  Don’t draw any general conclusions about VARCHAR(MAX) versus CHAR from this – I chose the length of the data specifically to expose this edge case.  In most cases, VARCHAR(MAX) performs very similarly to CHAR – I just wanted to make test 2 a bit more exciting. MAX Performance Summary: 8 seconds elapsed time 245MB memory grant 391MB tempdb usage 193MB estimated sort set 25,043 logical reads Sort warning Test 3 – TEXT The same test again, but using the deprecated TEXT data type for the padding column: DECLARE @read BIGINT, @write BIGINT ; SELECT @read = SUM(num_of_bytes_read), @write = SUM(num_of_bytes_written) FROM tempdb.sys.database_files AS DBF JOIN sys.dm_io_virtual_file_stats(2, NULL) AS FS ON FS.file_id = DBF.file_id WHERE DBF.type_desc = 'ROWS' ; SET STATISTICS IO ON ; SELECT TOP (150) TT.id, TT.padding FROM dbo.TestTEXT AS TT ORDER BY NEWID() OPTION (MAXDOP 1, RECOMPILE) ; SET STATISTICS IO OFF ; SELECT tempdb_read_MB = (SUM(num_of_bytes_read) - @read) / 1024. / 1024., tempdb_write_MB = (SUM(num_of_bytes_written) - @write) / 1024. / 1024., internal_use_MB = ( SELECT internal_objects_alloc_page_count / 128.0 FROM sys.dm_db_task_space_usage WHERE session_id = @@SPID ) FROM tempdb.sys.database_files AS DBF JOIN sys.dm_io_virtual_file_stats(2, NULL) AS FS ON FS.file_id = DBF.file_id WHERE DBF.type_desc = 'ROWS' ; This time the query runs in 500ms.  If you look at the metrics we have been checking so far, it’s not hard to understand why: TEXT Performance Summary: 0.5 seconds elapsed time 9MB memory grant 5MB tempdb usage 5MB estimated sort set 207 logical reads 596 LOB logical reads Sort warning SQL Server’s memory grant algorithm still underestimates the memory needed to perform the sorting operation, but the size of the data to sort is so much smaller (5MB versus 193MB previously) that the spilled sort doesn’t matter very much.  Why is the data size so much smaller?  The query still produces the correct results – including the large amount of data held in the padding column – so what magic is being performed here? TEXT versus MAX Storage The answer lies in how columns of the TEXT data type are stored.  By default, TEXT data is stored off-row in separate LOB pages – which explains why this is the first query we have seen that records LOB logical reads in its STATISTICS IO output.  You may recall from my last post that LOB data leaves an in-row pointer to the separate storage structure holding the LOB data. SQL Server can see that the full LOB value is not required by the query plan until results are returned, so instead of passing the full LOB value down the plan from the Clustered Index Scan, it passes the small in-row structure instead.  SQL Server estimates that each row coming from the scan will be 79 bytes long – 11 bytes for row overhead, 4 bytes for the integer id column, and 64 bytes for the LOB pointer (in fact the pointer is rather smaller – usually 16 bytes – but the details of that don’t really matter right now). OK, so this query is much more efficient because it is sorting a very much smaller data set – SQL Server delays retrieving the LOB data itself until after the Sort starts producing its 150 rows.  The question that normally arises at this point is: Why doesn’t SQL Server use the same trick when the padding column is defined as VARCHAR(MAX)? The answer is connected with the fact that if the actual size of the VARCHAR(MAX) data is 8000 bytes or less, it is usually stored in-row in exactly the same way as for a VARCHAR(8000) column – MAX data only moves off-row into LOB storage when it exceeds 8000 bytes.  The default behaviour of the TEXT type is to be stored off-row by default, unless the ‘text in row’ table option is set suitably and there is room on the page.  There is an analogous (but opposite) setting to control the storage of MAX data – the ‘large value types out of row’ table option.  By enabling this option for a table, MAX data will be stored off-row (in a LOB structure) instead of in-row.  SQL Server Books Online has good coverage of both options in the topic In Row Data. The MAXOOR Table The essential difference, then, is that MAX defaults to in-row storage, and TEXT defaults to off-row (LOB) storage.  You might be thinking that we could get the same benefits seen for the TEXT data type by storing the VARCHAR(MAX) values off row – so let’s look at that option now.  This script creates a fourth table, with the VARCHAR(MAX) data stored off-row in LOB pages: CREATE TABLE dbo.TestMAXOOR ( id INTEGER IDENTITY (1,1) NOT NULL, padding VARCHAR(MAX) NOT NULL,   CONSTRAINT [PK dbo.TestMAXOOR (id)] PRIMARY KEY CLUSTERED (id), ) ; EXECUTE sys.sp_tableoption @TableNamePattern = N'dbo.TestMAXOOR', @OptionName = 'large value types out of row', @OptionValue = 'true' ; SELECT large_value_types_out_of_row FROM sys.tables WHERE [schema_id] = SCHEMA_ID(N'dbo') AND name = N'TestMAXOOR' ; INSERT INTO dbo.TestMAXOOR WITH (TABLOCKX) ( padding ) SELECT SPACE(0) FROM dbo.TestCHAR ORDER BY id ; UPDATE TM WITH (TABLOCK) SET padding.WRITE (TC.padding, NULL, NULL) FROM dbo.TestMAXOOR AS TM JOIN dbo.TestCHAR AS TC ON TC.id = TM.id ; EXECUTE sys.sp_spaceused @objname = 'dbo.TestMAXOOR' ; CHECKPOINT ; Test 4 – MAXOOR We can now re-run our test on the MAXOOR (MAX out of row) table: DECLARE @read BIGINT, @write BIGINT ; SELECT @read = SUM(num_of_bytes_read), @write = SUM(num_of_bytes_written) FROM tempdb.sys.database_files AS DBF JOIN sys.dm_io_virtual_file_stats(2, NULL) AS FS ON FS.file_id = DBF.file_id WHERE DBF.type_desc = 'ROWS' ; SET STATISTICS IO ON ; SELECT TOP (150) MO.id, MO.padding FROM dbo.TestMAXOOR AS MO ORDER BY NEWID() OPTION (MAXDOP 1, RECOMPILE) ; SET STATISTICS IO OFF ; SELECT tempdb_read_MB = (SUM(num_of_bytes_read) - @read) / 1024. / 1024., tempdb_write_MB = (SUM(num_of_bytes_written) - @write) / 1024. / 1024., internal_use_MB = ( SELECT internal_objects_alloc_page_count / 128.0 FROM sys.dm_db_task_space_usage WHERE session_id = @@SPID ) FROM tempdb.sys.database_files AS DBF JOIN sys.dm_io_virtual_file_stats(2, NULL) AS FS ON FS.file_id = DBF.file_id WHERE DBF.type_desc = 'ROWS' ; TEXT Performance Summary: 0.3 seconds elapsed time 245MB memory grant 0MB tempdb usage 193MB estimated sort set 207 logical reads 446 LOB logical reads No sort warning The query runs very quickly – slightly faster than Test 3, and without spilling the sort to tempdb (there is no sort warning in the trace, and the monitoring query shows zero tempdb usage by this query).  SQL Server is passing the in-row pointer structure down the plan and only looking up the LOB value on the output side of the sort. The Hidden Problem There is still a huge problem with this query though – it requires a 245MB memory grant.  No wonder the sort doesn’t spill to tempdb now – 245MB is about 20 times more memory than this query actually requires to sort 50,000 records containing LOB data pointers.  Notice that the estimated row and data sizes in the plan are the same as in test 2 (where the MAX data was stored in-row). The optimizer assumes that MAX data is stored in-row, regardless of the sp_tableoption setting ‘large value types out of row’.  Why?  Because this option is dynamic – changing it does not immediately force all MAX data in the table in-row or off-row, only when data is added or actually changed.  SQL Server does not keep statistics to show how much MAX or TEXT data is currently in-row, and how much is stored in LOB pages.  This is an annoying limitation, and one which I hope will be addressed in a future version of the product. So why should we worry about this?  Excessive memory grants reduce concurrency and may result in queries waiting on the RESOURCE_SEMAPHORE wait type while they wait for memory they do not need.  245MB is an awful lot of memory, especially on 32-bit versions where memory grants cannot use AWE-mapped memory.  Even on a 64-bit server with plenty of memory, do you really want a single query to consume 0.25GB of memory unnecessarily?  That’s 32,000 8KB pages that might be put to much better use. The Solution The answer is not to use the TEXT data type for the padding column.  That solution happens to have better performance characteristics for this specific query, but it still results in a spilled sort, and it is hard to recommend the use of a data type which is scheduled for removal.  I hope it is clear to you that the fundamental problem here is that SQL Server sorts the whole set arriving at a Sort operator.  Clearly, it is not efficient to sort the whole table in memory just to return 150 rows in a random order. The TEXT example was more efficient because it dramatically reduced the size of the set that needed to be sorted.  We can do the same thing by selecting 150 unique keys from the table at random (sorting by NEWID() for example) and only then retrieving the large padding column values for just the 150 rows we need.  The following script implements that idea for all four tables: SET STATISTICS IO ON ; WITH TestTable AS ( SELECT * FROM dbo.TestCHAR ), TopKeys AS ( SELECT TOP (150) id FROM TestTable ORDER BY NEWID() ) SELECT T1.id, T1.padding FROM TestTable AS T1 WHERE T1.id = ANY (SELECT id FROM TopKeys) OPTION (MAXDOP 1) ; WITH TestTable AS ( SELECT * FROM dbo.TestMAX ), TopKeys AS ( SELECT TOP (150) id FROM TestTable ORDER BY NEWID() ) SELECT T1.id, T1.padding FROM TestTable AS T1 WHERE T1.id IN (SELECT id FROM TopKeys) OPTION (MAXDOP 1) ; WITH TestTable AS ( SELECT * FROM dbo.TestTEXT ), TopKeys AS ( SELECT TOP (150) id FROM TestTable ORDER BY NEWID() ) SELECT T1.id, T1.padding FROM TestTable AS T1 WHERE T1.id IN (SELECT id FROM TopKeys) OPTION (MAXDOP 1) ; WITH TestTable AS ( SELECT * FROM dbo.TestMAXOOR ), TopKeys AS ( SELECT TOP (150) id FROM TestTable ORDER BY NEWID() ) SELECT T1.id, T1.padding FROM TestTable AS T1 WHERE T1.id IN (SELECT id FROM TopKeys) OPTION (MAXDOP 1) ; SET STATISTICS IO OFF ; All four queries now return results in much less than a second, with memory grants between 6 and 12MB, and without spilling to tempdb.  The small remaining inefficiency is in reading the id column values from the clustered primary key index.  As a clustered index, it contains all the in-row data at its leaf.  The CHAR and VARCHAR(MAX) tables store the padding column in-row, so id values are separated by a 3999-character column, plus row overhead.  The TEXT and MAXOOR tables store the padding values off-row, so id values in the clustered index leaf are separated by the much-smaller off-row pointer structure.  This difference is reflected in the number of logical page reads performed by the four queries: Table 'TestCHAR' logical reads 25511 lob logical reads 000 Table 'TestMAX'. logical reads 25511 lob logical reads 000 Table 'TestTEXT' logical reads 00412 lob logical reads 597 Table 'TestMAXOOR' logical reads 00413 lob logical reads 446 We can increase the density of the id values by creating a separate nonclustered index on the id column only.  This is the same key as the clustered index, of course, but the nonclustered index will not include the rest of the in-row column data. CREATE UNIQUE NONCLUSTERED INDEX uq1 ON dbo.TestCHAR (id); CREATE UNIQUE NONCLUSTERED INDEX uq1 ON dbo.TestMAX (id); CREATE UNIQUE NONCLUSTERED INDEX uq1 ON dbo.TestTEXT (id); CREATE UNIQUE NONCLUSTERED INDEX uq1 ON dbo.TestMAXOOR (id); The four queries can now use the very dense nonclustered index to quickly scan the id values, sort them by NEWID(), select the 150 ids we want, and then look up the padding data.  The logical reads with the new indexes in place are: Table 'TestCHAR' logical reads 835 lob logical reads 0 Table 'TestMAX' logical reads 835 lob logical reads 0 Table 'TestTEXT' logical reads 686 lob logical reads 597 Table 'TestMAXOOR' logical reads 686 lob logical reads 448 With the new index, all four queries use the same query plan (click to enlarge): Performance Summary: 0.3 seconds elapsed time 6MB memory grant 0MB tempdb usage 1MB sort set 835 logical reads (CHAR, MAX) 686 logical reads (TEXT, MAXOOR) 597 LOB logical reads (TEXT) 448 LOB logical reads (MAXOOR) No sort warning I’ll leave it as an exercise for the reader to work out why trying to eliminate the Key Lookup by adding the padding column to the new nonclustered indexes would be a daft idea Conclusion This post is not about tuning queries that access columns containing big strings.  It isn’t about the internal differences between TEXT and MAX data types either.  It isn’t even about the cool use of UPDATE .WRITE used in the MAXOOR table load.  No, this post is about something else: Many developers might not have tuned our starting example query at all – 5 seconds isn’t that bad, and the original query plan looks reasonable at first glance.  Perhaps the NEWID() function would have been blamed for ‘just being slow’ – who knows.  5 seconds isn’t awful – unless your users expect sub-second responses – but using 250MB of memory and writing 200MB to tempdb certainly is!  If ten sessions ran that query at the same time in production that’s 2.5GB of memory usage and 2GB hitting tempdb.  Of course, not all queries can be rewritten to avoid large memory grants and sort spills using the key-lookup technique in this post, but that’s not the point either. The point of this post is that a basic understanding of execution plans is not enough.  Tuning for logical reads and adding covering indexes is not enough.  If you want to produce high-quality, scalable TSQL that won’t get you paged as soon as it hits production, you need a deep understanding of execution plans, and as much accurate, deep knowledge about SQL Server as you can lay your hands on.  The advanced database developer has a wide range of tools to use in writing queries that perform well in a range of circumstances. By the way, the examples in this post were written for SQL Server 2008.  They will run on 2005 and demonstrate the same principles, but you won’t get the same figures I did because 2005 had a rather nasty bug in the Top N Sort operator.  Fair warning: if you do decide to run the scripts on a 2005 instance (particularly the parallel query) do it before you head out for lunch… This post is dedicated to the people of Christchurch, New Zealand. © 2011 Paul White email: @[email protected] twitter: @SQL_Kiwi

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• Sniffing out SQL Code Smells: Inconsistent use of Symbolic names and Datatypes

  - by Phil Factor

  It is an awkward feeling. You’ve just delivered a database application that seems to be working fine in production, and you just run a few checks on it. You discover that there is a potential bug that, out of sheer good chance, hasn’t kicked in to produce an error; but it lurks, like a smoking bomb. Worse, maybe you find that the bug has started its evil work of corrupting the data, but in ways that nobody has, so far detected. You investigate, and find the damage. You are somehow going to have to repair it. Yes, it still very occasionally happens to me. It is not a nice feeling, and I do anything I can to prevent it happening. That’s why I’m interested in SQL code smells. SQL Code Smells aren’t necessarily bad practices, but just show you where to focus your attention when checking an application. Sometimes with databases the bugs can be subtle. SQL is rather like HTML: the language does its best to try to carry out your wishes, rather than to be picky about your bugs. Most of the time, this is a great benefit, but not always. One particular place where this can be detrimental is where you have implicit conversion between different data types. Most of the time it is completely harmless but we’re  concerned about the occasional time it isn’t. Let’s give an example: String truncation. Let’s give another even more frightening one, rounding errors on assignment to a number of different precision. Each requires a blog-post to explain in detail and I’m not now going to try. Just remember that it is not always a good idea to assign data to variables, parameters or even columns when they aren’t the same datatype, especially if you are relying on implicit conversion to work its magic.For details of the problem and the consequences, see here:  SR0014: Data loss might occur when casting from {Type1} to {Type2} . For any experienced Database Developer, this is a more frightening read than a Vampire Story. This is why one of the SQL Code Smells that makes me edgy, in my own or other peoples’ code, is to see parameters, variables and columns that have the same names and different datatypes. Whereas quite a lot of this is perfectly normal and natural, you need to check in case one of two things have gone wrong. Either sloppy naming, or mixed datatypes. Sure it is hard to remember whether you decided that the length of a log entry was 80 or 100 characters long, or the precision of a number. That is why a little check like this I’m going to show you is excellent for tidying up your code before you check it back into source Control! 1/ Checking Parameters only If you were just going to check parameters, you might just do this. It simply groups all the parameters, either input or output, of all the routines (e.g. stored procedures or functions) by their name and checks to see, in the HAVING clause, whether their data types are all the same. If not, it lists all the examples and their origin (the routine) Even this little check can occasionally be scarily revealing. ;WITH userParameter AS  ( SELECT   c.NAME AS ParameterName,  OBJECT_SCHEMA_NAME(c.object_ID) + '.' + OBJECT_NAME(c.object_ID) AS ObjectName,  t.name + ' '     + CASE     --we may have to put in the length            WHEN t.name IN ('char', 'varchar', 'nchar', 'nvarchar')             THEN '('               + CASE WHEN c.max_length = -1 THEN 'MAX'                ELSE CONVERT(VARCHAR(4),                    CASE WHEN t.name IN ('nchar', 'nvarchar')                      THEN c.max_length / 2 ELSE c.max_length                    END)                END + ')'         WHEN t.name IN ('decimal', 'numeric')             THEN '(' + CONVERT(VARCHAR(4), c.precision)                   + ',' + CONVERT(VARCHAR(4), c.Scale) + ')'         ELSE ''      END  --we've done with putting in the length      + CASE WHEN XML_collection_ID <> 0         THEN --deal with object schema names             '(' + CASE WHEN is_XML_Document = 1                    THEN 'DOCUMENT '                    ELSE 'CONTENT '                   END              + COALESCE(               (SELECT QUOTENAME(ss.name) + '.' + QUOTENAME(sc.name)                FROM sys.xml_schema_collections sc                INNER JOIN Sys.Schemas ss ON sc.schema_ID = ss.schema_ID                WHERE sc.xml_collection_ID = c.XML_collection_ID),'NULL') + ')'          ELSE ''         END        AS [DataType]  FROM sys.parameters c  INNER JOIN sys.types t ON c.user_Type_ID = t.user_Type_ID  WHERE OBJECT_SCHEMA_NAME(c.object_ID) <> 'sys'   AND parameter_id>0)SELECT CONVERT(CHAR(80),objectName+'.'+ParameterName),DataType FROM UserParameterWHERE ParameterName IN   (SELECT ParameterName FROM UserParameter    GROUP BY ParameterName    HAVING MIN(Datatype)<>MAX(DataType))ORDER BY ParameterName   so, in a very small example here, we have a @ClosingDelimiter variable that is only CHAR(1) when, by the looks of it, it should be up to ten characters long, or even worse, a function that should be a char(1) and seems to let in a string of ten characters. Worth investigating. Then we have a @Comment variable that can't decide whether it is a VARCHAR(2000) or a VARCHAR(MAX) 2/ Columns and Parameters Actually, once we’ve cleared up the mess we’ve made of our parameter-naming in the database we’re inspecting, we’re going to be more interested in listing both columns and parameters. We can do this by modifying the routine to list columns as well as parameters. Because of the slight complexity of creating the string version of the datatypes, we will create a fake table of both columns and parameters so that they can both be processed the same way. After all, we want the datatypes to match Unfortunately, parameters do not expose all the attributes we are interested in, such as whether they are nullable (oh yes, subtle bugs happen if this isn’t consistent for a datatype). We’ll have to leave them out for this check. Voila! A slight modification of the first routine ;WITH userObject AS  ( SELECT   Name AS DataName,--the actual name of the parameter or column ('@' removed)  --and the qualified object name of the routine  OBJECT_SCHEMA_NAME(ObjectID) + '.' + OBJECT_NAME(ObjectID) AS ObjectName,  --now the harder bit: the definition of the datatype.  TypeName + ' '     + CASE     --we may have to put in the length. e.g. CHAR (10)           WHEN TypeName IN ('char', 'varchar', 'nchar', 'nvarchar')             THEN '('               + CASE WHEN MaxLength = -1 THEN 'MAX'                ELSE CONVERT(VARCHAR(4),                    CASE WHEN TypeName IN ('nchar', 'nvarchar')                      THEN MaxLength / 2 ELSE MaxLength                    END)                END + ')'         WHEN TypeName IN ('decimal', 'numeric')--a BCD number!             THEN '(' + CONVERT(VARCHAR(4), Precision)                   + ',' + CONVERT(VARCHAR(4), Scale) + ')'         ELSE ''      END  --we've done with putting in the length      + CASE WHEN XML_collection_ID <> 0 --tush tush. XML         THEN --deal with object schema names             '(' + CASE WHEN is_XML_Document = 1                    THEN 'DOCUMENT '                    ELSE 'CONTENT '                   END              + COALESCE(               (SELECT TOP 1 QUOTENAME(ss.name) + '.' + QUOTENAME(sc.Name)                FROM sys.xml_schema_collections sc                INNER JOIN Sys.Schemas ss ON sc.schema_ID = ss.schema_ID                WHERE sc.xml_collection_ID = XML_collection_ID),'NULL') + ')'          ELSE ''         END        AS [DataType],       DataObjectType  FROM   (Select t.name AS TypeName, REPLACE(c.name,'@','') AS Name,          c.max_length AS MaxLength, c.precision AS [Precision],           c.scale AS [Scale], c.[Object_id] AS ObjectID, XML_collection_ID,          is_XML_Document,'P' AS DataobjectType  FROM sys.parameters c  INNER JOIN sys.types t ON c.user_Type_ID = t.user_Type_ID  AND parameter_id>0  UNION all  Select t.name AS TypeName, c.name AS Name, c.max_length AS MaxLength,          c.precision AS [Precision], c.scale AS [Scale],          c.[Object_id] AS ObjectID, XML_collection_ID,is_XML_Document,          'C' AS DataobjectType            FROM sys.columns c  INNER JOIN sys.types t ON c.user_Type_ID = t.user_Type_ID   WHERE OBJECT_SCHEMA_NAME(c.object_ID) <> 'sys'  )f)SELECT CONVERT(CHAR(80),objectName+'.'   + CASE WHEN DataobjectType ='P' THEN '@' ELSE '' END + DataName),DataType FROM UserObjectWHERE DataName IN   (SELECT DataName FROM UserObject   GROUP BY DataName    HAVING MIN(Datatype)<>MAX(DataType))ORDER BY DataName     Hmm. I can tell you I found quite a few minor issues with the various tabases I tested this on, and found some potential bugs that really leap out at you from the results. Here is the start of the result for AdventureWorks. Yes, AccountNumber is, for some reason, a Varchar(10) in the Customer table. Hmm. odd. Why is a city fifty characters long in that view?  The idea of the description of a colour being 256 characters long seems over-ambitious. Go down the list and you'll spot other mistakes. There are no bugs, but just mess. We started out with a listing to examine parameters, then we mixed parameters and columns. Our last listing is for a slightly more in-depth look at table columns. You’ll notice that we’ve delibarately removed the indication of whether a column is persisted, or is an identity column because that gives us false positives for our code smells. If you just want to browse your metadata for other reasons (and it can quite help in some circumstances) then uncomment them! ;WITH userColumns AS  ( SELECT   c.NAME AS columnName,  OBJECT_SCHEMA_NAME(c.object_ID) + '.' + OBJECT_NAME(c.object_ID) AS ObjectName,  REPLACE(t.name + ' '   + CASE WHEN is_computed = 1 THEN ' AS ' + --do DDL for a computed column          (SELECT definition FROM sys.computed_columns cc           WHERE cc.object_id = c.object_id AND cc.column_ID = c.column_ID)     --we may have to put in the length            WHEN t.Name IN ('char', 'varchar', 'nchar', 'nvarchar')             THEN '('               + CASE WHEN c.Max_Length = -1 THEN 'MAX'                ELSE CONVERT(VARCHAR(4),                    CASE WHEN t.Name IN ('nchar', 'nvarchar')                      THEN c.Max_Length / 2 ELSE c.Max_Length                    END)                END + ')'       WHEN t.name IN ('decimal', 'numeric')       THEN '(' + CONVERT(VARCHAR(4), c.precision) + ',' + CONVERT(VARCHAR(4), c.Scale) + ')'       ELSE ''      END + CASE WHEN c.is_rowguidcol = 1          THEN ' ROWGUIDCOL'          ELSE ''         END + CASE WHEN XML_collection_ID <> 0            THEN --deal with object schema names             '(' + CASE WHEN is_XML_Document = 1                THEN 'DOCUMENT '                ELSE 'CONTENT '               END + COALESCE((SELECT                QUOTENAME(ss.name) + '.' + QUOTENAME(sc.name)                FROM                sys.xml_schema_collections sc                INNER JOIN Sys.Schemas ss ON sc.schema_ID = ss.schema_ID                WHERE                sc.xml_collection_ID = c.XML_collection_ID),                'NULL') + ')'            ELSE ''           END + CASE WHEN is_identity = 1             THEN CASE WHEN OBJECTPROPERTY(object_id,                'IsUserTable') = 1 AND COLUMNPROPERTY(object_id,                c.name,                'IsIDNotForRepl') = 0 AND OBJECTPROPERTY(object_id,                'IsMSShipped') = 0                THEN ''                ELSE ' NOT FOR REPLICATION '               END             ELSE ''            END + CASE WHEN c.is_nullable = 0               THEN ' NOT NULL'               ELSE ' NULL'              END + CASE                WHEN c.default_object_id <> 0                THEN ' DEFAULT ' + object_Definition(c.default_object_id)                ELSE ''               END + CASE                WHEN c.collation_name IS NULL                THEN ''                WHEN c.collation_name <> (SELECT                collation_name                FROM                sys.databases                WHERE                name = DB_NAME()) COLLATE Latin1_General_CI_AS                THEN COALESCE(' COLLATE ' + c.collation_name,                '')                ELSE ''                END,'  ',' ') AS [DataType]FROM sys.columns c  INNER JOIN sys.types t ON c.user_Type_ID = t.user_Type_ID  WHERE OBJECT_SCHEMA_NAME(c.object_ID) <> 'sys')SELECT CONVERT(CHAR(80),objectName+'.'+columnName),DataType FROM UserColumnsWHERE columnName IN (SELECT columnName FROM UserColumns  GROUP BY columnName  HAVING MIN(Datatype)<>MAX(DataType))ORDER BY columnName If you take a look down the results against Adventureworks, you'll see once again that there are things to investigate, mostly, in the illustration, discrepancies between null and non-null datatypes So I here you ask, what about temporary variables within routines? If ever there was a source of elusive bugs, you'll find it there. Sadly, these temporary variables are not stored in the metadata so we'll have to find a more subtle way of flushing these out, and that will, I'm afraid, have to wait!

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• How to optimize this mysql query - explain output included

  - by Sandeepan Nath

  This is the query (a search query basically, based on tags):- select SUM(DISTINCT(ttagrels.id_tag in (2105,2120,2151,2026,2046) )) as key_1_total_matches, td.*, u.* from Tutors_Tag_Relations AS ttagrels Join Tutor_Details AS td ON td.id_tutor = ttagrels.id_tutor JOIN Users as u on u.id_user = td.id_user where (ttagrels.id_tag in (2105,2120,2151,2026,2046)) group by td.id_tutor HAVING key_1_total_matches = 1 And following is the database dump needed to execute this query:- CREATE TABLE IF NOT EXISTS `Users` ( `id_user` int(10) unsigned NOT NULL auto_increment, `id_group` int(11) NOT NULL default '0', PRIMARY KEY (`id_user`), KEY `Users_FKIndex1` (`id_group`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 AUTO_INCREMENT=730 ; INSERT INTO `Users` (`id_user`, `id_group`) VALUES (303, 1); CREATE TABLE IF NOT EXISTS `Tutor_Details` ( `id_tutor` int(10) unsigned NOT NULL auto_increment, `id_user` int(10) NOT NULL default '0', PRIMARY KEY (`id_tutor`), KEY `Users_FKIndex1` (`id_user`), KEY `id_user` (`id_user`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=58 ; INSERT INTO `Tutor_Details` (`id_tutor`, `id_user`) VALUES (26, 303); CREATE TABLE IF NOT EXISTS `Tags` ( `id_tag` int(10) unsigned NOT NULL auto_increment, `tag` varchar(255) default NULL, PRIMARY KEY (`id_tag`), UNIQUE KEY `tag` (`tag`), KEY `id_tag` (`id_tag`), KEY `tag_2` (`tag`), KEY `tag_3` (`tag`), KEY `tag_4` (`tag`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=2957 ; INSERT INTO `Tags` (`id_tag`, `tag`) VALUES (2026, 'Brendan.\nIn'), (2046, 'Brendan.'), (2105, 'Brendan'), (2120, 'Brendan''s'), (2151, 'Brendan)'); CREATE TABLE IF NOT EXISTS `Tutors_Tag_Relations` ( `id_tag` int(10) unsigned NOT NULL default '0', `id_tutor` int(10) unsigned default NULL, `tutor_field` varchar(255) default NULL, `cdate` timestamp NOT NULL default CURRENT_TIMESTAMP, `udate` timestamp NULL default NULL, KEY `Tutors_Tag_Relations` (`id_tag`), KEY `id_tutor` (`id_tutor`), KEY `id_tag` (`id_tag`), KEY `id_tutor_2` (`id_tutor`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1; INSERT INTO `Tutors_Tag_Relations` (`id_tag`, `id_tutor`, `tutor_field`, `cdate`, `udate`) VALUES (2105, 26, 'firstname', '2010-06-17 17:08:45', NULL); ALTER TABLE `Tutors_Tag_Relations` ADD CONSTRAINT `Tutors_Tag_Relations_ibfk_2` FOREIGN KEY (`id_tutor`) REFERENCES `Tutor_Details` (`id_tutor`) ON DELETE NO ACTION ON UPDATE NO ACTION, ADD CONSTRAINT `Tutors_Tag_Relations_ibfk_1` FOREIGN KEY (`id_tag`) REFERENCES `Tags` (`id_tag`) ON DELETE NO ACTION ON UPDATE NO ACTION; What the query does? This query actually searches tutors which contain "Brendan"(as their name or biography or something). The id_tags 2105,2120,2151,2026,2046 are nothing but the tags which are LIKE "%Brendan%". My question is :- 1.In the explain of this query, the reference column shows NULL for ttagrels, but there are possible keys (Tutors_Tag_Relations,id_tutor,id_tag,id_tutor_2). So, why is no key being taken. How to make the query take references. Is it possible at all? 2. The other two tables td and u are using references. Any indexing needed in those? I think not. Check the explain query output here http://www.test.examvillage.com/explain.png

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• The Excel Column Name assigment problem

  - by Peter Larsson

  Here is a generic algorithm to get the Excel column name according to it's position. By changing the @Base parameter, you can do this for any sequence according to same style as Excel. DECLARE @Value INT = 8839,         @Base TINYINT = 26   ;WITH cteSequence(Value, Delta, Quote, Base, Chr) AS (     SELECT  CAST(@Value AS INT) AS Value,             CAST(1 AS INT) AS Delta,             CAST(@Base AS INT) AS Quote,             CAST(@Base AS INT) AS Base,             CHAR(65 +(@Value - 1) % @Base) AS Chr       UNION ALL       SELECT  Value AS Value,             Quote AS Delta,             26 * Quote AS Quote,             Base AS Base,             CHAR(65 +((Value - Delta)/ Quote - 1) % Base) AS Chr     FROM    cteSequence     WHERE   CHAR(65 +((Value - Delta)/ Quote - 1) % Base) <> '@' ) SELECT  CAST(Msg AS VARCHAR(MAX)) FROM    (             SELECT        '' + Chr             FROM        cteSequence             ORDER BY    Delta DESC             FOR XML        PATH('')         ) AS x(Msg)

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