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  • Do 7.2k SATA drives and a hardware raid controller always end with trouble?

    - by xelco52
    I'm reading the FreeNAS userguide and came across the statement: Note that hardware RAID configured as JBOD may still detach disks that do not respond in time; and as such may require TLER/CCTL/ERC-enabled disks to prevent drive dropouts. I'm using a '3Ware 9550SX-8LP RAID Controller' and see quite a few stories of people successfully running raid5 on 7.2k consumer SATA drives without issue. Are detached disks only a theoretical problem, or should I expect this to be a common occurrence?

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  • Maintainance backup in sql2005

    - by Visharth Asthana
    I changed my administrator and Sql password for server but when I try to create the backup in maintainance plan then I get this error message "Exception has been thrown by the target of invocation (MSCORLIB)" A sql statement was issued and failed. Please revert me because same thing I applied for another server it was worked properly. Regards Visharth

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  • Redirect command line into its own output?

    - by mfinni
    Windows CMD shell - any easy way of redirecting the command itself into the output? If I do net localgroup administrators %computername%-admins.txt, I'd like the output file to contain the net statement as well. No powershell available to me; pure CMD/COMMAND only. This is for an audit; the auditors want to see what command generated the output. I'm trying to avoid screenshots or enormous copy-paste from CMD windows.

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  • Getting template metaprogramming compile-time constants at runtime

    - by GMan - Save the Unicorns
    Background Consider the following: template <unsigned N> struct Fibonacci { enum { value = Fibonacci<N-1>::value + Fibonacci<N-2>::value }; }; template <> struct Fibonacci<1> { enum { value = 1 }; }; template <> struct Fibonacci<0> { enum { value = 0 }; }; This is a common example and we can get the value of a Fibonacci number as a compile-time constant: int main(void) { std::cout << "Fibonacci(15) = "; std::cout << Fibonacci<15>::value; std::cout << std::endl; } But you obviously cannot get the value at runtime: int main(void) { std::srand(static_cast<unsigned>(std::time(0))); // ensure the table exists up to a certain size // (even though the rest of the code won't work) static const unsigned fibbMax = 20; Fibonacci<fibbMax>::value; // get index into sequence unsigned fibb = std::rand() % fibbMax; std::cout << "Fibonacci(" << fibb << ") = "; std::cout << Fibonacci<fibb>::value; std::cout << std::endl; } Because fibb is not a compile-time constant. Question So my question is: What is the best way to peek into this table at run-time? The most obvious solution (and "solution" should be taken lightly), is to have a large switch statement: unsigned fibonacci(unsigned index) { switch (index) { case 0: return Fibonacci<0>::value; case 1: return Fibonacci<1>::value; case 2: return Fibonacci<2>::value; . . . case 20: return Fibonacci<20>::value; default: return fibonacci(index - 1) + fibonacci(index - 2); } } int main(void) { std::srand(static_cast<unsigned>(std::time(0))); static const unsigned fibbMax = 20; // get index into sequence unsigned fibb = std::rand() % fibbMax; std::cout << "Fibonacci(" << fibb << ") = "; std::cout << fibonacci(fibb); std::cout << std::endl; } But now the size of the table is very hard coded and it wouldn't be easy to expand it to say, 40. The only one I came up with that has a similiar method of query is this: template <int TableSize = 40> class FibonacciTable { public: enum { max = TableSize }; static unsigned get(unsigned index) { if (index == TableSize) { return Fibonacci<TableSize>::value; } else { // too far, pass downwards return FibonacciTable<TableSize - 1>::get(index); } } }; template <> class FibonacciTable<0> { public: enum { max = 0 }; static unsigned get(unsigned) { // doesn't matter, no where else to go. // must be 0, or the original value was // not in table return 0; } }; int main(void) { std::srand(static_cast<unsigned>(std::time(0))); // get index into sequence unsigned fibb = std::rand() % FibonacciTable<>::max; std::cout << "Fibonacci(" << fibb << ") = "; std::cout << FibonacciTable<>::get(fibb); std::cout << std::endl; } Which seems to work great. The only two problems I see are: Potentially large call stack, since calculating Fibonacci<2 requires we go through TableMax all the way to 2, and: If the value is outside of the table, it returns zero as opposed to calculating it. So is there something I am missing? It seems there should be a better way to pick out these values at runtime. A template metaprogramming version of a switch statement perhaps, that generates a switch statement up to a certain number? Thanks in advance.

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  • strange output in ubuntu terminal when running a lex program

    - by Max
    Hi. I'm running a lexical analyzer using lex, and I've got it mostly correct, but my terminal gives strange output once I take out an ECHO statement I was using to help debug the code. With that statement, my output looks like this: max@Max-Ubuntu:~/Desktop/Compiler Project/project2$ ./a.out <../cmmFiles/expression.cmm VOIDID(){ INTID,ID,ID; BOOLID,ID,ID; ID(ID); ID(ID); ID(ID); ID(ID); ID=-ID-NUM+ID/NUM*(-NUM+ID*IDNUM); ID(ID); ID=ID>ID||ID>=ID; IF(ID)ID(NUM);ELSEID(NUM); ID=ID<ID&&ID<=ID; IF(ID==TRUE)ID(NUM);ELSEID(NUM); ID=ID&&!ID||!ID&&ID; IF(ID!=FALSE)ID(NUM);ELSEID(NUM); } While hard to read, that output is correct. Once I take out the ECHO statement, I instead get this: max@Max-Ubuntu:~/Desktop/Compiler Project/project2$ ./a.out <../cmmFiles/expression.cmm }F(ID!=FALSE)ID(NUM);ELSEID(NUM);; It looks like it's only outputting the final line, except with an extraneous } near the beginning, what looks like half an IF token immediately after, and an extraneous ; at the end. Is this some quirk of my terminal, or does removing that ECHO cause my lexer to screw up that badly? I'm hesitant to keep working until I know for sure what's going on here. Thanks for any answers. Here's my lexer: %{ /* definitions of manifest constants -reserved words- BOOL, ELSE, IF, TRUE, WHILE, DO, FALSE, INT, VOID -Punctuation and operators- LPAREN, RPAREN, LBRACK, RBRACK, LBRACE, RBRACE, SEMI, COMMA, PLUS, MINUS, TIMES, DIV, MOD, AND, OR, NOT, IS, ADDR, EQ, NE, LT, GT, LE, GE -Other tokens- NUMBER, ID, PUNCT, OP */ #include <stdio.h> #include <stdlib.h> //#include "y.tab.h" //int line = 1, numAttr; //char *strAttr; %} /* regular definitions */ delim [ \t] ws {delim}+ start "/*" one [^*] two "*" three [^*/] end "/" comment {start}({one}*{two}+{three})*{one}*{two}+{end} letter [A-Za-z] digit [0-9] id ({letter}|_)({letter}|{digit}|_)* number {digit}+ %% {ws} { /*no action and no return */} {comment} { /*no action and no return */} [\n] {ECHO; /*no action */} // <-- this is the ECHO in question. bool { printf("BOOL");} else { printf("ELSE");} if { printf("IF");} true { printf("TRUE");} while { printf("WHILE");} do { printf("DO");} false { printf("FALSE");} int { printf("INT");} void { printf("VOID");} {id} { printf("ID");} {number} { printf("NUM");} "(" { printf("(");} ")" { printf(")");} "[" { printf("[");} "]" { printf("]");} "{" { printf("{");} "}" { printf("}");} ";" { printf(";");} "," { printf(",");} "+" { printf("+");} "-" { printf("-");} "*" { printf("*");} "/" { printf("/");} "%" { printf("%");} "&" { printf("&");} "&&" { printf("&&");} "||" { printf("||");} "!" { printf("!");} "!=" { printf("!=");} "=" { printf("=");} "==" { printf("==");} "<" { printf("<");} "<=" { printf("<=");} ">" { printf(">");} ">=" { printf(">=");} %% int main() { yylex(); printf("\n"); } int yywrap(void) { return 1; } here's the file it's analyzing: /* this program * illustrates evaluation of * arithmetic and boolean * expressions */ void main( ) { int m,n,p; bool a,b,c; scan(m); print(m); scan(n); print(n); p=-m-3+n/2*(-5+m*n%4); print(p); a=m>n || n>=p; if (a) print(1); else print(0); b=m<n && n<=p; if (b==true) print(1); else print(0); c=a && !b || !a && b; if (c!=false) print(1); else print(0); }

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  • What does Ruby have that Python doesn't, and vice versa?

    - by Lennart Regebro
    There is a lot of discussions of Python vs Ruby, and I all find them completely unhelpful, because they all turn around why feature X sucks in language Y, or that claim language Y doesn't have X, although in fact it does. I also know exactly why I prefer Python, but that's also subjective, and wouldn't help anybody choosing, as they might not have the same tastes in development as I do. It would therefore be interesting to list the differences, objectively. So no "Python's lambdas sucks". Instead explain what Ruby's lambdas can do that Python's can't. No subjectivity. Example code is good! Don't have several differences in one answer, please. And vote up the ones you know are correct, and down those you know are incorrect (or are subjective). Also, differences in syntax is not interesting. We know Python does with indentation what Ruby does with brackets and ends, and that @ is called self in Python. UPDATE: This is now a community wiki, so we can add the big differences here. Ruby has a class reference in the class body In Ruby you have a reference to the class (self) already in the class body. In Python you don't have a reference to the class until after the class construction is finished. An example: class Kaka puts self end self in this case is the class, and this code would print out "Kaka". There is no way to print out the class name or in other ways access the class from the class definition body in Python. All classes are mutable in Ruby This lets you develop extensions to core classes. Here's an example of a rails extension: class String def starts_with?(other) head = self[0, other.length] head == other end end Ruby has Perl-like scripting features Ruby has first class regexps, $-variables, the awk/perl line by line input loop and other features that make it more suited to writing small shell scripts that munge text files or act as glue code for other programs. Ruby has first class continuations Thanks to the callcc statement. In Python you can create continuations by various techniques, but there is no support built in to the language. Ruby has blocks With the "do" statement you can create a multi-line anonymous function in Ruby, which will be passed in as an argument into the method in front of do, and called from there. In Python you would instead do this either by passing a method or with generators. Ruby: amethod { |here| many=lines+of+code goes(here) } Python: def function(here): many=lines+of+code goes(here) amethod(function) Interestingly, the convenience statement in Ruby for calling a block is called "yield", which in Python will create a generator. Ruby: def themethod yield 5 end themethod do |foo| puts foo end Python: def themethod(): yield 5 for foo in themethod: print foo Although the principles are different, the result is strikingly similar. Python has built-in generators (which are used like Ruby blocks, as noted above) Python has support for generators in the language. In Ruby you could use the generator module that uses continuations to create a generator from a block. Or, you could just use a block/proc/lambda! Moreover, in Ruby 1.9 Fibers are, and can be used as, generators. docs.python.org has this generator example: def reverse(data): for index in range(len(data)-1, -1, -1): yield data[index] Contrast this with the above block examples. Python has flexible name space handling In Ruby, when you import a file with require, all the things defined in that file will end up in your global namespace. This causes namespace pollution. The solution to that is Rubys modules. But if you create a namespace with a module, then you have to use that namespace to access the contained classes. In Python, the file is a module, and you can import its contained names with from themodule import *, thereby polluting the namespace if you want. But you can also import just selected names with from themodule import aname, another or you can simply import themodule and then access the names with themodule.aname. If you want more levels in your namespace you can have packages, which are directories with modules and an __init__.py file. Python has docstrings Docstrings are strings that are attached to modules, functions and methods and can be introspected at runtime. This helps for creating such things as the help command and automatic documentation. def frobnicate(bar): """frobnicate takes a bar and frobnicates it >>> bar = Bar() >>> bar.is_frobnicated() False >>> frobnicate(bar) >>> bar.is_frobnicated() True """ Python has more libraries Python has a vast amount of available modules and bindings for libraries. Python has multiple inheritance Ruby does not ("on purpose" -- see Ruby's website, see here how it's done in Ruby). It does reuse the module concept as a sort of abstract classes. Python has list/dict comprehensions Python: res = [x*x for x in range(1, 10)] Ruby: res = (0..9).map { |x| x * x } Python: >>> (x*x for x in range(10)) <generator object <genexpr> at 0xb7c1ccd4> >>> list(_) [0, 1, 4, 9, 16, 25, 36, 49, 64, 81] Ruby: p = proc { |x| x * x } (0..9).map(&p) Python: >>> {x:str(y*y) for x,y in {1:2, 3:4}.items()} {1: '4', 3: '16'} Ruby: >> Hash[{1=>2, 3=>4}.map{|x,y| [x,(y*y).to_s]}] => {1=>"4", 3=>"16"} Python has decorators Things similar to decorators can be created in Ruby, and it can also be argued that they aren't as necessary as in Python.

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  • Ignoring focusLost(), SWT.Verify, or other SWT listeners in Java code.

    - by Zoot
    Outside of the actual SWT listener, is there any way to ignore a listener via code? For example, I have a java program that implements SWT Text Widgets, and the widgets have: SWT.Verify listeners to filter out unwanted text input. ModifyListeners to wait for the correct number of valid input characters and automatically set focus (using setFocus())to the next valid field, skipping the other text widgets in the tab order. focusLost(FocusEvent) FocusListeners that wait for the loss of focus from the text widget to perform additional input verification and execute an SQL query based on the user input. The issue I run into is clearing the text widgets. One of the widgets has the format "####-##" (Four Numbers, a hyphen, then two numbers) and I have implemented this listener, which is a modified version of SWT Snippet Snippet179. The initial text for this text widget is " - " to provide visual feedback to the user as to the expected format. Only numbers are acceptable input, and the program automatically skips past the hyphen at the appropriate point. /* * This listener was adapted from the "verify input in a template (YYYY/MM/DD)" SWT Code * Snippet (also known as Snippet179), from the Snippets page of the SWT Project. * SWT Code Snippets can be found at: * http://www.eclipse.org/swt/snippets/ */ textBox.addListener(SWT.Verify, new Listener() { boolean ignore; public void handleEvent(Event e) { if (ignore) return; e.doit = false; StringBuffer buffer = new StringBuffer(e.text); char[] chars = new char[buffer.length()]; buffer.getChars(0, chars.length, chars, 0); if (e.character == '\b') { for (int i = e.start; i < e.end; i++) { switch (i) { case 0: /* [x]xxx-xx */ case 1: /* x[x]xx-xx */ case 2: /* xx[x]x-xx */ case 3: /* xxx[x]-xx */ case 5: /* xxxx-[x]x */ case 6: /* xxxx-x[x] */ { buffer.append(' '); break; } case 4: /* xxxx[-]xx */ { buffer.append('-'); break; } default: return; } } textBox.setSelection(e.start, e.start + buffer.length()); ignore = true; textBox.insert(buffer.toString()); ignore = false; textBox.setSelection(e.start, e.start); return; } int start = e.start; if (start > 6) return; int index = 0; for (int i = 0; i < chars.length; i++) { if (start + index == 4) { if (chars[i] == '-') { index++; continue; } buffer.insert(index++, '-'); } if (chars[i] < '0' || '9' < chars[i]) return; index++; } String newText = buffer.toString(); int length = newText.length(); textBox.setSelection(e.start, e.start + length); ignore = true; textBox.insert(newText); ignore = false; /* * After a valid key press, verifying if the input is completed * and passing the cursor to the next text box. */ if (7 == textBox.getCaretPosition()) { /* * Attempting to change the text after receiving a known valid input that has no results (0000-00). */ if ("0000-00".equals(textBox.getText())) { // "0000-00" is the special "Erase Me" code for these text boxes. ignore = true; textBox.setText(" - "); ignore = false; } // Changing focus to a different textBox by using "setFocus()" method. differentTextBox.setFocus(); } } } ); As you can see, the only method I've figured out to clear this text widget from a different point in the code is by assigning "0000-00" textBox.setText("000000") and checking for that input in the listener. When that input is received, the listener changes the text back to " - " (four spaces, a hyphen, then two spaces). There is also a focusLost Listener that parses this text widget for spaces, then in order to avoid unnecessary SQL queries, it clears/resets all fields if the input is invalid (i.e contains spaces). // Adding focus listener to textBox to wait for loss of focus to perform SQL statement. textBox.addFocusListener(new FocusAdapter() { @Override public void focusLost(FocusEvent evt) { // Get the contents of otherTextBox and textBox. (otherTextBox must be <= textBox) String boxFour = otherTextBox.getText(); String boxFive = textBox.getText(); // If either text box has spaces in it, don't perform the search. if (boxFour.contains(" ") || boxFive.contains(" ")) { // Don't perform SQL statements. Debug statement. System.out.println("Tray Position input contains spaces. Ignoring."); //Make all previous results invisible, if any. labels.setVisible(false); differentTextBox.setText(""); labelResults.setVisible(false); } else { //... Perform SQL statement ... } } } ); OK. Often, I use SWT MessageBox widgets in this code to communicate to the user, or wish to change the text widgets back to an empty state after verifying the input. The problem is that messageboxes seem to create a focusLost event, and using the .setText(string) method is subject to SWT.Verify listeners that are present on the text widget. Any suggestions as to selectively ignoring these listeners in code, but keeping them present for all other user input? Thank you in advance for your assistance.

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  • How do you control what your C compiler Optimizes?

    - by Jordan S
    I am writing the firmware for an embedded device in C using the Silicon Labs IDE and the SDCC compiler. The device architecture is based on the 8051 family. The function in question is shown below. The function is used to set the ports on my MCU to drive a stepper motor. It gets called in by an interrupt handler. The big switch statement just sets the ports to the proper value for the next motor step. The bottom part of the function looks at an input from a hall effect sensor and a number of steps moved in order to detect if the motor has stalled. The problem is, for some reason the second IF statement that looks like this if (StallDetector > (GapSize + 20)) { HandleStallEvent(); } always seems to get optimized out. If I try to put a breakpoint at the HandleStallEvent() call the IDE gives me a message saying "No Address Correlation to this line number". I am not really good enough at reading assembly to tell what it is doing but I have pasted a snippet from the asm output below. Any help would be much appreciated. void OperateStepper(void) { //static bit LastHomeMagState = HomeSensor; static bit LastPosMagState = PosSensor; if(PulseMotor) { if(MoveDirection == 1) // Go clockwise { switch(STEPPER_POSITION) { case 'A': STEPPER_POSITION = 'B'; P1 = 0xFD; break; case 'B': STEPPER_POSITION = 'C'; P1 = 0xFF; break; case 'C': STEPPER_POSITION = 'D'; P1 = 0xFE; break; case 'D': STEPPER_POSITION = 'A'; P1 = 0xFC; break; default: STEPPER_POSITION = 'A'; P1 = 0xFC; } //end switch } else // Go CounterClockwise { switch(STEPPER_POSITION) { case 'A': STEPPER_POSITION = 'D'; P1 = 0xFE; break; case 'B': STEPPER_POSITION = 'A'; P1 = 0xFC; break; case 'C': STEPPER_POSITION = 'B'; P1 = 0xFD; break; case 'D': STEPPER_POSITION = 'C'; P1 = 0xFF; break; default: STEPPER_POSITION = 'A'; P1 = 0xFE; } //end switch } //end else MotorSteps++; StallDetector++; if(PosSensor != LastPosMagState) { StallDetector = 0; LastPosMagState = PosSensor; } else { if (PosSensor == ON) { if (StallDetector > (MagnetSize + 20)) { HandleStallEvent(); } } else if (PosSensor == OFF) { if (StallDetector > (GapSize + 20)) { HandleStallEvent(); } } } } //end if PulseMotor } ... and the asm output for the the bottom part of this function... ; C:\SiLabs\Optec Programs\HSFW_HID_SDCC_2\MotionControl.c:653: if(PosSensor != LastPosMagState) mov c,_P1_4 jb _OperateStepper_LastPosMagState_1_1,00158$ cpl c 00158$: jc 00126$ C$MotionControl.c$655$3$7 ==. ; C:\SiLabs\Optec Programs\HSFW_HID_SDCC_2\MotionControl.c:655: StallDetector = 0; clr a mov _StallDetector,a mov (_StallDetector + 1),a C$MotionControl.c$657$3$7 ==. ; C:\SiLabs\Optec Programs\HSFW_HID_SDCC_2\MotionControl.c:657: LastPosMagState = PosSensor; mov c,_P1_4 mov _OperateStepper_LastPosMagState_1_1,c ret 00126$: C$MotionControl.c$661$2$8 ==. ; C:\SiLabs\Optec Programs\HSFW_HID_SDCC_2\MotionControl.c:661: if (PosSensor == ON) jb _P1_4,00123$ C$MotionControl.c$663$4$9 ==. ; C:\SiLabs\Optec Programs\HSFW_HID_SDCC_2\MotionControl.c:663: if (StallDetector > (MagnetSize + 20)) mov a,_MagnetSize mov r2,a rlc a subb a,acc mov r3,a mov a,#0x14 add a,r2 mov r2,a clr a addc a,r3 mov r3,a clr c mov a,r2 subb a,_StallDetector mov a,r3 subb a,(_StallDetector + 1) jnc 00130$ C$MotionControl.c$665$5$10 ==. ; C:\SiLabs\Optec Programs\HSFW_HID_SDCC_2\MotionControl.c:665: HandleStallEvent(); ljmp _HandleStallEvent 00123$: C$MotionControl.c$668$2$8 ==. ; C:\SiLabs\Optec Programs\HSFW_HID_SDCC_2\MotionControl.c:668: else if (PosSensor == OFF) jnb _P1_4,00130$ C$MotionControl.c$670$4$11 ==. ; C:\SiLabs\Optec Programs\HSFW_HID_SDCC_2\MotionControl.c:670: if (StallDetector > (GapSize + 20)) mov a,#0x14 add a,_GapSize mov r2,a clr a addc a,(_GapSize + 1) mov r3,a clr c mov a,r2 subb a,_StallDetector mov a,r3 subb a,(_StallDetector + 1) jnc 00130$ C$MotionControl.c$672$5$12 ==. ; C:\SiLabs\Optec Programs\HSFW_HID_SDCC_2\MotionControl.c:672: HandleStallEvent(); C$MotionControl.c$678$2$1 ==. XG$OperateStepper$0$0 ==. ljmp _HandleStallEvent 00130$: ret It looks to me like the compiler is NOT optimizing out this second if statement from the looks of the asm but if that is the case why does the IDE not allow me so set a breakpoint there? Maybe it's just a dumb IDE!

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  • Embedding generic sql queries into c# program

    - by Pooja Balkundi
    Okay referring to my first question code in the main, I want the user to enter employee name at runtime and then i take this name which user has entered and compare it with the e_name of my emp table , if it exists i want to display all information of that employee , how can I achieve this ? using System; using System.Collections.Generic; using System.Linq; using System.Windows.Forms; using MySql.Data.MySqlClient; namespace ConnectCsharppToMySQL { public class DBConnect { private MySqlConnection connection; private string server; private string database; private string uid; private string password; string name; //Constructor public DBConnect() { Initialize(); } //Initialize values private void Initialize() { server = "localhost"; database = "test"; uid = "root"; password = ""; string connectionString; connectionString = "SERVER=" + server + ";" + "DATABASE=" + database + ";" + "UID=" + uid + ";" + "PASSWORD=" + password + ";"; connection = new MySqlConnection(connectionString); } //open connection to database private bool OpenConnection() { try { connection.Open(); return true; } catch (MySqlException ex) { //When handling errors, you can your application's response based //on the error number. //The two most common error numbers when connecting are as follows: //0: Cannot connect to server. //1045: Invalid user name and/or password. switch (ex.Number) { case 0: MessageBox.Show("Cannot connect to server. Contact administrator"); break; case 1045: MessageBox.Show("Invalid username/password, please try again"); break; } return false; } } //Close connection private bool CloseConnection() { try { connection.Close(); return true; } catch (MySqlException ex) { MessageBox.Show(ex.Message); return false; } } //Insert statement public void Insert() { string query = "INSERT INTO emp (e_name, age) VALUES('Pooja R', '21')"; //open connection if (this.OpenConnection() == true) { //create command and assign the query and connection from the constructor MySqlCommand cmd = new MySqlCommand(query, connection); //Execute command cmd.ExecuteNonQuery(); //close connection this.CloseConnection(); } } //Update statement public void Update() { string query = "UPDATE emp SET e_name='Peachy', age='22' WHERE e_name='Pooja R'"; //Open connection if (this.OpenConnection() == true) { //create mysql command MySqlCommand cmd = new MySqlCommand(); //Assign the query using CommandText cmd.CommandText = query; //Assign the connection using Connection cmd.Connection = connection; //Execute query cmd.ExecuteNonQuery(); //close connection this.CloseConnection(); } } //Select statement public List<string>[] Select() { string query = "SELECT * FROM emp where e_name=(/*I WANT USER ENTERED NAME TO GET INSERTED HERE*/)"; //Create a list to store the result List<string>[] list = new List<string>[3]; list[0] = new List<string>(); list[1] = new List<string>(); list[2] = new List<string>(); //Open connection if (this.OpenConnection() == true) { //Create Command MySqlCommand cmd = new MySqlCommand(query, connection); //Create a data reader and Execute the command MySqlDataReader dataReader = cmd.ExecuteReader(); //Read the data and store them in the list while (dataReader.Read()) { list[0].Add(dataReader["e_id"] + ""); list[1].Add(dataReader["e_name"] + ""); list[2].Add(dataReader["age"] + ""); } //close Data Reader dataReader.Close(); //close Connection this.CloseConnection(); //return list to be displayed return list; } else { return list; } } public static void Main(String[] args) { DBConnect db1 = new DBConnect(); Console.WriteLine("Initializing"); db1.Initialize(); Console.WriteLine("Search :"); Console.WriteLine("Enter the employee name"); db1.name = Console.ReadLine(); db1.Select(); Console.ReadLine(); } } }

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  • Different behavior for REF CURSOR between Oracle 10g and 11g when unique index present?

    - by wweicker
    Description I have an Oracle stored procedure that has been running for 7 or so years both locally on development instances and on multiple client test and production instances running Oracle 8, then 9, then 10, and recently 11. It has worked consistently until the upgrade to Oracle 11g. Basically, the procedure opens a reference cursor, updates a table then completes. In 10g the cursor will contain the expected results but in 11g the cursor will be empty. No DML or DDL changed after the upgrade to 11g. This behavior is consistent on every 10g or 11g instance I've tried (10.2.0.3, 10.2.0.4, 11.1.0.7, 11.2.0.1 - all running on Windows). The specific code is much more complicated but to explain the issue in somewhat realistic overview: I have some data in a header table and a bunch of child tables that will be output to PDF. The header table has a boolean (NUMBER(1) where 0 is false and 1 is true) column indicating whether that data has been processed yet. The view is limited to only show rows in that have not been processed (the view also joins on some other tables, makes some inline queries and function calls, etc). So at the time when the cursor is opened, the view shows one or more rows, then after the cursor is opened an update statement runs to flip the flag in the header table, a commit is issued, then the procedure completes. On 10g, the cursor opens, it contains the row, then the update statement flips the flag and running the procedure a second time would yield no data. On 11g, the cursor never contains the row, it's as if the cursor does not open until after the update statement runs. I'm concerned that something may have changed in 11g (hopefully a setting that can be configured) that might affect other procedures and other applications. What I'd like to know is whether anyone knows why the behavior is different between the two database versions and whether the issue can be resolved without code changes. Update 1: I managed to track the issue down to a unique constraint. It seems that when the unique constraint is present in 11g the issue is reproducible 100% of the time regardless of whether I'm running the real world code against the actual objects or the following simple example. Update 2: I was able to completely eliminate the view from the equation. I have updated the simple example to show the problem exists even when querying directly against the table. Simple Example CREATE TABLE tbl1 ( col1 VARCHAR2(10), col2 NUMBER(1) ); INSERT INTO tbl1 (col1, col2) VALUES ('TEST1', 0); /* View is no longer required to demonstrate the problem CREATE OR REPLACE VIEW vw1 (col1, col2) AS SELECT col1, col2 FROM tbl1 WHERE col2 = 0; */ CREATE OR REPLACE PACKAGE pkg1 AS TYPE refWEB_CURSOR IS REF CURSOR; PROCEDURE proc1 (crs OUT refWEB_CURSOR); END pkg1; CREATE OR REPLACE PACKAGE BODY pkg1 IS PROCEDURE proc1 (crs OUT refWEB_CURSOR) IS BEGIN OPEN crs FOR SELECT col1 FROM tbl1 WHERE col1 = 'TEST1' AND col2 = 0; UPDATE tbl1 SET col2 = 1 WHERE col1 = 'TEST1'; COMMIT; END proc1; END pkg1; Anonymous Block Demo DECLARE crs1 pkg1.refWEB_CURSOR; TYPE rectype1 IS RECORD ( col1 vw1.col1%TYPE ); rec1 rectype1; BEGIN pkg1.proc1 ( crs1 ); DBMS_OUTPUT.PUT_LINE('begin first test'); LOOP FETCH crs1 INTO rec1; EXIT WHEN crs1%NOTFOUND; DBMS_OUTPUT.PUT_LINE(rec1.col1); END LOOP; DBMS_OUTPUT.PUT_LINE('end first test'); END; /* After creating this index, the problem is seen */ CREATE UNIQUE INDEX unique_col1 ON tbl1 (col1); /* Reset data to initial values */ TRUNCATE TABLE tbl1; INSERT INTO tbl1 (col1, col2) VALUES ('TEST1', 0); DECLARE crs1 pkg1.refWEB_CURSOR; TYPE rectype1 IS RECORD ( col1 vw1.col1%TYPE ); rec1 rectype1; BEGIN pkg1.proc1 ( crs1 ); DBMS_OUTPUT.PUT_LINE('begin second test'); LOOP FETCH crs1 INTO rec1; EXIT WHEN crs1%NOTFOUND; DBMS_OUTPUT.PUT_LINE(rec1.col1); END LOOP; DBMS_OUTPUT.PUT_LINE('end second test'); END; Example of what the output on 10g would be:   begin first test   TEST1   end first test   begin second test   TEST1   end second test Example of what the output on 11g would be:   begin first test   TEST1   end first test   begin second test   end second test Clarification I can't remove the COMMIT because in the real world scenario the procedure is called from a web application. When the data provider on the front end calls the procedure it will issue an implicit COMMIT when disconnecting from the database anyways. So if I remove the COMMIT in the procedure then yes, the anonymous block demo would work but the real world scenario would not because the COMMIT would still happen. Question Why is 11g behaving differently? Is there anything I can do other than re-write the code?

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  • Displaying Multiple Tables in a Page in Jasper Reports using ireports/Jasper Assistant

    - by Karthikeyan
    Hi all, I have a report to be printed / exported to PDF format. for that i am using jasper reports. I have 8 individual pages to be exported. so i prepared 8 separate design files. In that 6 pages are having more static text and mere direct mapping and remaining two pages consists of table like data. one page contains huge table so i filled it directly with no problem by keeping a single table in detail band. now problem is that remaining one page. that page is having more than 5 small tables (two or four column). is t possible to have more that one table in a page in jasper reports ? i am using jasper reports and for designing jasper assistant/ireports.

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  • Creating packages in code – Execute SQL Task

    The Execute SQL Task is for obvious reasons very well used, so I thought if you are building packages in code the chances are you will be using it. Using the task basic features of the task are quite straightforward, add the task and set some properties, just like any other. When you start interacting with variables though it can be a little harder to grasp so these samples should see you through. Some of these more advanced features are explained in much more detail in our ever popular post The Execute SQL Task, here I’ll just be showing you how to implement them in code. The abbreviated code blocks below demonstrate the different features of the task. The complete code has been encapsulated into a sample class which you can download (ExecSqlPackage.cs). Each feature described has its own method in the sample class which is mentioned after the code block. This first sample just shows adding the task, setting the basic properties for a connection and of course an SQL statement. Package package = new Package(); // Add the SQL OLE-DB connection ConnectionManager sqlConnection = AddSqlConnection(package, "localhost", "master"); // Add the SQL Task package.Executables.Add("STOCK:SQLTask"); // Get the task host wrapper TaskHost taskHost = package.Executables[0] as TaskHost; // Set required properties taskHost.Properties["Connection"].SetValue(taskHost, sqlConnection.ID); taskHost.Properties["SqlStatementSource"].SetValue(taskHost, "SELECT * FROM sysobjects"); For the full version of this code, see the CreatePackage method in the sample class. The AddSqlConnection method is a helper method that adds an OLE-DB connection to the package, it is of course in the sample class file too. Returning a single value with a Result Set The following sample takes a different approach, getting a reference to the ExecuteSQLTask object task itself, rather than just using the non-specific TaskHost as above. Whilst it means we need to add an extra reference to our project (Microsoft.SqlServer.SQLTask) it makes coding much easier as we have compile time validation of any property and types we use. For the more complex properties that is very valuable and saves a lot of time during development. The query has also been changed to return a single value, one row and one column. The sample shows how we can return that value into a variable, which we also add to our package in the code. To do this manually you would set the Result Set property on the General page to Single Row and map the variable on the Result Set page in the editor. Package package = new Package(); // Add the SQL OLE-DB connection ConnectionManager sqlConnection = AddSqlConnection(package, "localhost", "master"); // Add the SQL Task package.Executables.Add("STOCK:SQLTask"); // Get the task host wrapper TaskHost taskHost = package.Executables[0] as TaskHost; // Add variable to hold result value package.Variables.Add("Variable", false, "User", 0); // Get the task object ExecuteSQLTask task = taskHost.InnerObject as ExecuteSQLTask; // Set core properties task.Connection = sqlConnection.Name; task.SqlStatementSource = "SELECT id FROM sysobjects WHERE name = 'sysrowsets'"; // Set single row result set task.ResultSetType = ResultSetType.ResultSetType_SingleRow; // Add result set binding, map the id column to variable task.ResultSetBindings.Add(); IDTSResultBinding resultBinding = task.ResultSetBindings.GetBinding(0); resultBinding.ResultName = "id"; resultBinding.DtsVariableName = "User::Variable"; For the full version of this code, see the CreatePackageResultVariable method in the sample class. The other types of Result Set behaviour are just a variation on this theme, set the property and map the result binding as required. Parameter Mapping for SQL Statements This final example uses a parameterised SQL statement, with the coming from a variable. The syntax varies slightly between connection types, as explained in the Working with Parameters and Return Codes in the Execute SQL Taskhelp topic, but OLE-DB is the most commonly used, for which a question mark is the parameter value placeholder. Package package = new Package(); // Add the SQL OLE-DB connection ConnectionManager sqlConnection = AddSqlConnection(package, ".", "master"); // Add the SQL Task package.Executables.Add("STOCK:SQLTask"); // Get the task host wrapper TaskHost taskHost = package.Executables[0] as TaskHost; // Get the task object ExecuteSQLTask task = taskHost.InnerObject as ExecuteSQLTask; // Set core properties task.Connection = sqlConnection.Name; task.SqlStatementSource = "SELECT id FROM sysobjects WHERE name = ?"; // Add variable to hold parameter value package.Variables.Add("Variable", false, "User", "sysrowsets"); // Add input parameter binding task.ParameterBindings.Add(); IDTSParameterBinding parameterBinding = task.ParameterBindings.GetBinding(0); parameterBinding.DtsVariableName = "User::Variable"; parameterBinding.ParameterDirection = ParameterDirections.Input; parameterBinding.DataType = (int)OleDBDataTypes.VARCHAR; parameterBinding.ParameterName = "0"; parameterBinding.ParameterSize = 255; For the full version of this code, see the CreatePackageParameterVariable method in the sample class. You’ll notice the data type has to be specified for the parameter IDTSParameterBinding .DataType Property, and these type codes are connection specific too. My enumeration I wrote several years ago is shown below was probably done by reverse engineering a package and also the API header file, but I recently found a very handy post that covers more connections as well for exactly this, Setting the DataType of IDTSParameterBinding objects (Execute SQL Task). /// <summary> /// Enumeration of OLE-DB types, used when mapping OLE-DB parameters. /// </summary> private enum OleDBDataTypes { BYTE = 0x11, CURRENCY = 6, DATE = 7, DB_VARNUMERIC = 0x8b, DBDATE = 0x85, DBTIME = 0x86, DBTIMESTAMP = 0x87, DECIMAL = 14, DOUBLE = 5, FILETIME = 0x40, FLOAT = 4, GUID = 0x48, LARGE_INTEGER = 20, LONG = 3, NULL = 1, NUMERIC = 0x83, NVARCHAR = 130, SHORT = 2, SIGNEDCHAR = 0x10, ULARGE_INTEGER = 0x15, ULONG = 0x13, USHORT = 0x12, VARCHAR = 0x81, VARIANT_BOOL = 11 } Download Sample code ExecSqlPackage.cs (10KB)

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  • Bugzilla ./testserver.pl failing

    - by SomeKittens
    root@KittensTest:/var/www/Bugzilla/bugzilla-4.2.1# ./testserver.pl http://localhost/Bugzilla/bugzilla-4.2.1 TEST-OK Webserver is running under group id in $webservergroup. TEST-OK Got padlock picture. TEST-FAILED Webserver is fetching rather than executing CGI files. Check the AddHandler statement in your httpd.conf file. Well then. httpd.conf (from here[2.2.4.1.1]): <Directory /var/www/Bugzilla/bugzilla-4.2.1> AddHandler cgi-script .cgi .pl Options +Indexes +Includes +ExecCGI DirectoryIndex index.cgi AllowOverride Limit FileInfo Indexes </Directory> What am I doing wrong? I'm pretty new to this (first Bugzilla install), so I'll appreciate explanation.

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  • Setup Remote Access in Windows Home Server

    - by Mysticgeek
    One of the many awesome features of Windows Home Server, is the ability to access your server and other computers on your network remotely. Today we show you the steps to enable Remote Access to your home server from anywhere you have an Internet connection. Remote Access in Windows Home Server has a lot of great features like uploading and downloading files from shared folders, accessing files from machines on your network, and controling machines remotely (on supported OS versions). Here we take a look at the basics of setting it up, choosing a domain name, and verifying you can connect remotely. Setup Remote Access in Windows Home Server Open the Windows Home Server Console and click on Settings. Next select Remote Access, it is off by default, just click the button to turn it on. Wait while your router is configured for remote access, when it’s complete click Next. Notice that it will enable UPnP, if you don’t wish to have that enabled, you can manually forward the correct ports. If you have any problems with the router being automatically configured, we’ll be taking a look at a more detailed troubleshooting guide in the future. The router is successfully configured, and we can continue to the next process of configuring our domain name. The Domain Name Setup Wizard will start. Notice you will need a Windows Live ID to set it up –which is typically your hotmail address. If you don’t already have one, you can get one here. Type in your Live ID email address and password and click Next… Agree to the Home Server Privacy Statement and the Live Custom Domains Addendum. If you’re concerned about privacy and want to learn more about the domain addendum, make sure to read about it before agreeing. There is nothing abnormal to point out about either statement, but if this is your first time setting it up, it’s good to review the information.   Now choose a name for the domain. You should select something that is easy to remember and identifies your home server. The name can contain up to 63 characters, numbers, letters, and hyphens…and must begin and end with a letter or number. When you have the name figured out click the Confirm button. Note: You can only register one domain name per Live ID. If the name isn’t already taken, you’ll get a confirmation message indicating it’s god to go. The wizard is complete and you can now access the home server from the URL provided. A few other things to point out after you’ve set it up…under Domain Name click on the Details button… Which pulls up the domain detail information and you can refresh the data to verify everything is working correctly. Or you can click the Configure button and then change or release your current domain name. Under Web site settings, you can change you site page headline to whatever you want it to be. Accessing Home Server Remotely After you’ve gotten everything setup for your home server domain, you can begin to access it when you’re away from home. Simply type in the domain address you created in the previous steps. The start page is rather boring…and to start accessing your data, click the Log On button in the upper right hand corner. Then enter in your home server credentials to gain access to your files, folders, and network computers. You won’t be able to log in with your administrator user account however, to protect security of your network. Once you’re logged in, you’ll be able to access different parts of your home server shares and network computers. Conclusion Now that you have Remote Access setup, you should be able to access and manage your files easily. Being able to access data from your home server remotely is great when you need to get certain files while on the road. The web UI is pretty self explanatory, works best in IE as ActiveX is required, and is smooth and easy to work with. In future articles we’ll be covering a lot more regarding remote access, including more of the available features, troubleshooting connection issues, and enabling access for other users. Similar Articles Productive Geek Tips GMedia Blog: Setting Up a Windows Home ServerHow to Remote Desktop to the Actual Server Console on Windows 2003Use Windows Vista Aero through Remote Desktop ConnectionAccess Your MySQL Server Remotely Over SSHShare Ubuntu Home Directories using Samba TouchFreeze Alternative in AutoHotkey The Icy Undertow Desktop Windows Home Server – Backup to LAN The Clear & Clean Desktop Use This Bookmarklet to Easily Get Albums Use AutoHotkey to Assign a Hotkey to a Specific Window Latest Software Reviews Tinyhacker Random Tips DVDFab 6 Revo Uninstaller Pro Registry Mechanic 9 for Windows PC Tools Internet Security Suite 2010 Penolo Lets You Share Sketches On Twitter Visit Woolyss.com for Old School Games, Music and Videos Add a Custom Title in IE using Spybot or Spyware Blaster When You Need to Hail a Taxi in NYC Live Map of Marine Traffic NoSquint Remembers Site Specific Zoom Levels (Firefox)

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  • Creating packages in code – Execute SQL Task

    The Execute SQL Task is for obvious reasons very well used, so I thought if you are building packages in code the chances are you will be using it. Using the task basic features of the task are quite straightforward, add the task and set some properties, just like any other. When you start interacting with variables though it can be a little harder to grasp so these samples should see you through. Some of these more advanced features are explained in much more detail in our ever popular post The Execute SQL Task, here I’ll just be showing you how to implement them in code. The abbreviated code blocks below demonstrate the different features of the task. The complete code has been encapsulated into a sample class which you can download (ExecSqlPackage.cs). Each feature described has its own method in the sample class which is mentioned after the code block. This first sample just shows adding the task, setting the basic properties for a connection and of course an SQL statement. Package package = new Package(); // Add the SQL OLE-DB connection ConnectionManager sqlConnection = AddSqlConnection(package, "localhost", "master"); // Add the SQL Task package.Executables.Add("STOCK:SQLTask"); // Get the task host wrapper TaskHost taskHost = package.Executables[0] as TaskHost; // Set required properties taskHost.Properties["Connection"].SetValue(taskHost, sqlConnection.ID); taskHost.Properties["SqlStatementSource"].SetValue(taskHost, "SELECT * FROM sysobjects"); For the full version of this code, see the CreatePackage method in the sample class. The AddSqlConnection method is a helper method that adds an OLE-DB connection to the package, it is of course in the sample class file too. Returning a single value with a Result Set The following sample takes a different approach, getting a reference to the ExecuteSQLTask object task itself, rather than just using the non-specific TaskHost as above. Whilst it means we need to add an extra reference to our project (Microsoft.SqlServer.SQLTask) it makes coding much easier as we have compile time validation of any property and types we use. For the more complex properties that is very valuable and saves a lot of time during development. The query has also been changed to return a single value, one row and one column. The sample shows how we can return that value into a variable, which we also add to our package in the code. To do this manually you would set the Result Set property on the General page to Single Row and map the variable on the Result Set page in the editor. Package package = new Package(); // Add the SQL OLE-DB connection ConnectionManager sqlConnection = AddSqlConnection(package, "localhost", "master"); // Add the SQL Task package.Executables.Add("STOCK:SQLTask"); // Get the task host wrapper TaskHost taskHost = package.Executables[0] as TaskHost; // Add variable to hold result value package.Variables.Add("Variable", false, "User", 0); // Get the task object ExecuteSQLTask task = taskHost.InnerObject as ExecuteSQLTask; // Set core properties task.Connection = sqlConnection.Name; task.SqlStatementSource = "SELECT id FROM sysobjects WHERE name = 'sysrowsets'"; // Set single row result set task.ResultSetType = ResultSetType.ResultSetType_SingleRow; // Add result set binding, map the id column to variable task.ResultSetBindings.Add(); IDTSResultBinding resultBinding = task.ResultSetBindings.GetBinding(0); resultBinding.ResultName = "id"; resultBinding.DtsVariableName = "User::Variable"; For the full version of this code, see the CreatePackageResultVariable method in the sample class. The other types of Result Set behaviour are just a variation on this theme, set the property and map the result binding as required. Parameter Mapping for SQL Statements This final example uses a parameterised SQL statement, with the coming from a variable. The syntax varies slightly between connection types, as explained in the Working with Parameters and Return Codes in the Execute SQL Taskhelp topic, but OLE-DB is the most commonly used, for which a question mark is the parameter value placeholder. Package package = new Package(); // Add the SQL OLE-DB connection ConnectionManager sqlConnection = AddSqlConnection(package, ".", "master"); // Add the SQL Task package.Executables.Add("STOCK:SQLTask"); // Get the task host wrapper TaskHost taskHost = package.Executables[0] as TaskHost; // Get the task object ExecuteSQLTask task = taskHost.InnerObject as ExecuteSQLTask; // Set core properties task.Connection = sqlConnection.Name; task.SqlStatementSource = "SELECT id FROM sysobjects WHERE name = ?"; // Add variable to hold parameter value package.Variables.Add("Variable", false, "User", "sysrowsets"); // Add input parameter binding task.ParameterBindings.Add(); IDTSParameterBinding parameterBinding = task.ParameterBindings.GetBinding(0); parameterBinding.DtsVariableName = "User::Variable"; parameterBinding.ParameterDirection = ParameterDirections.Input; parameterBinding.DataType = (int)OleDBDataTypes.VARCHAR; parameterBinding.ParameterName = "0"; parameterBinding.ParameterSize = 255; For the full version of this code, see the CreatePackageParameterVariable method in the sample class. You’ll notice the data type has to be specified for the parameter IDTSParameterBinding .DataType Property, and these type codes are connection specific too. My enumeration I wrote several years ago is shown below was probably done by reverse engineering a package and also the API header file, but I recently found a very handy post that covers more connections as well for exactly this, Setting the DataType of IDTSParameterBinding objects (Execute SQL Task). /// <summary> /// Enumeration of OLE-DB types, used when mapping OLE-DB parameters. /// </summary> private enum OleDBDataTypes { BYTE = 0x11, CURRENCY = 6, DATE = 7, DB_VARNUMERIC = 0x8b, DBDATE = 0x85, DBTIME = 0x86, DBTIMESTAMP = 0x87, DECIMAL = 14, DOUBLE = 5, FILETIME = 0x40, FLOAT = 4, GUID = 0x48, LARGE_INTEGER = 20, LONG = 3, NULL = 1, NUMERIC = 0x83, NVARCHAR = 130, SHORT = 2, SIGNEDCHAR = 0x10, ULARGE_INTEGER = 0x15, ULONG = 0x13, USHORT = 0x12, VARCHAR = 0x81, VARIANT_BOOL = 11 } Download Sample code ExecSqlPackage.cs (10KB)

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  • SQL SERVER – Simple Example of Snapshot Isolation – Reduce the Blocking Transactions

    - by pinaldave
    To learn any technology and move to a more advanced level, it is very important to understand the fundamentals of the subject first. Today, we will be talking about something which has been quite introduced a long time ago but not properly explored when it comes to the isolation level. Snapshot Isolation was introduced in SQL Server in 2005. However, the reality is that there are still many software shops which are using the SQL Server 2000, and therefore cannot be able to maintain the Snapshot Isolation. Many software shops have upgraded to the later version of the SQL Server, but their respective developers have not spend enough time to upgrade themselves with the latest technology. “It works!” is a very common answer of many when they are asked about utilizing the new technology, instead of backward compatibility commands. In one of the recent consultation project, I had same experience when developers have “heard about it” but have no idea about snapshot isolation. They were thinking it is the same as Snapshot Replication – which is plain wrong. This is the same demo I am including here which I have created for them. In Snapshot Isolation, the updated row versions for each transaction are maintained in TempDB. Once a transaction has begun, it ignores all the newer rows inserted or updated in the table. Let us examine this example which shows the simple demonstration. This transaction works on optimistic concurrency model. Since reading a certain transaction does not block writing transaction, it also does not block the reading transaction, which reduced the blocking. First, enable database to work with Snapshot Isolation. Additionally, check the existing values in the table from HumanResources.Shift. ALTER DATABASE AdventureWorks SET ALLOW_SNAPSHOT_ISOLATION ON GO SELECT ModifiedDate FROM HumanResources.Shift GO Now, we will need two different sessions to prove this example. First Session: Set Transaction level isolation to snapshot and begin the transaction. Update the column “ModifiedDate” to today’s date. -- Session 1 SET TRANSACTION ISOLATION LEVEL SNAPSHOT BEGIN TRAN UPDATE HumanResources.Shift SET ModifiedDate = GETDATE() GO Please note that we have not yet been committed to the transaction. Now, open the second session and run the following “SELECT” statement. Then, check the values of the table. Please pay attention on setting the Isolation level for the second one as “Snapshot” at the same time when we already start the transaction using BEGIN TRAN. -- Session 2 SET TRANSACTION ISOLATION LEVEL SNAPSHOT BEGIN TRAN SELECT ModifiedDate FROM HumanResources.Shift GO You will notice that the values in the table are still original values. They have not been modified yet. Once again, go back to session 1 and begin the transaction. -- Session 1 COMMIT After that, go back to Session 2 and see the values of the table. -- Session 2 SELECT ModifiedDate FROM HumanResources.Shift GO You will notice that the values are yet not changed and they are still the same old values which were there right in the beginning of the session. Now, let us commit the transaction in the session 2. Once committed, run the same SELECT statement once more and see what the result is. -- Session 2 COMMIT SELECT ModifiedDate FROM HumanResources.Shift GO You will notice that it now reflects the new updated value. I hope that this example is clear enough as it would give you good idea how the Snapshot Isolation level works. There is much more to write about an extra level, READ_COMMITTED_SNAPSHOT, which we will be discussing in another post soon. If you wish to use this transaction’s Isolation level in your production database, I would appreciate your comments about their performance on your servers. I have included here the complete script used in this example for your quick reference. ALTER DATABASE AdventureWorks SET ALLOW_SNAPSHOT_ISOLATION ON GO SELECT ModifiedDate FROM HumanResources.Shift GO -- Session 1 SET TRANSACTION ISOLATION LEVEL SNAPSHOT BEGIN TRAN UPDATE HumanResources.Shift SET ModifiedDate = GETDATE() GO -- Session 2 SET TRANSACTION ISOLATION LEVEL SNAPSHOT BEGIN TRAN SELECT ModifiedDate FROM HumanResources.Shift GO -- Session 1 COMMIT -- Session 2 SELECT ModifiedDate FROM HumanResources.Shift GO -- Session 2 COMMIT SELECT ModifiedDate FROM HumanResources.Shift GO Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Pinal Dave, SQL, SQL Authority, SQL Performance, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: Transaction Isolation

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  • SQL SERVER – Simple Example of Snapshot Isolation – Reduce the Blocking Transactions

    - by pinaldave
    To learn any technology and move to a more advanced level, it is very important to understand the fundamentals of the subject first. Today, we will be talking about something which has been quite introduced a long time ago but not properly explored when it comes to the isolation level. Snapshot Isolation was introduced in SQL Server in 2005. However, the reality is that there are still many software shops which are using the SQL Server 2000, and therefore cannot be able to maintain the Snapshot Isolation. Many software shops have upgraded to the later version of the SQL Server, but their respective developers have not spend enough time to upgrade themselves with the latest technology. “It works!” is a very common answer of many when they are asked about utilizing the new technology, instead of backward compatibility commands. In one of the recent consultation project, I had same experience when developers have “heard about it” but have no idea about snapshot isolation. They were thinking it is the same as Snapshot Replication – which is plain wrong. This is the same demo I am including here which I have created for them. In Snapshot Isolation, the updated row versions for each transaction are maintained in TempDB. Once a transaction has begun, it ignores all the newer rows inserted or updated in the table. Let us examine this example which shows the simple demonstration. This transaction works on optimistic concurrency model. Since reading a certain transaction does not block writing transaction, it also does not block the reading transaction, which reduced the blocking. First, enable database to work with Snapshot Isolation. Additionally, check the existing values in the table from HumanResources.Shift. ALTER DATABASE AdventureWorks SET ALLOW_SNAPSHOT_ISOLATION ON GO SELECT ModifiedDate FROM HumanResources.Shift GO Now, we will need two different sessions to prove this example. First Session: Set Transaction level isolation to snapshot and begin the transaction. Update the column “ModifiedDate” to today’s date. -- Session 1 SET TRANSACTION ISOLATION LEVEL SNAPSHOT BEGIN TRAN UPDATE HumanResources.Shift SET ModifiedDate = GETDATE() GO Please note that we have not yet been committed to the transaction. Now, open the second session and run the following “SELECT” statement. Then, check the values of the table. Please pay attention on setting the Isolation level for the second one as “Snapshot” at the same time when we already start the transaction using BEGIN TRAN. -- Session 2 SET TRANSACTION ISOLATION LEVEL SNAPSHOT BEGIN TRAN SELECT ModifiedDate FROM HumanResources.Shift GO You will notice that the values in the table are still original values. They have not been modified yet. Once again, go back to session 1 and begin the transaction. -- Session 1 COMMIT After that, go back to Session 2 and see the values of the table. -- Session 2 SELECT ModifiedDate FROM HumanResources.Shift GO You will notice that the values are yet not changed and they are still the same old values which were there right in the beginning of the session. Now, let us commit the transaction in the session 2. Once committed, run the same SELECT statement once more and see what the result is. -- Session 2 COMMIT SELECT ModifiedDate FROM HumanResources.Shift GO You will notice that it now reflects the new updated value. I hope that this example is clear enough as it would give you good idea how the Snapshot Isolation level works. There is much more to write about an extra level, READ_COMMITTED_SNAPSHOT, which we will be discussing in another post soon. If you wish to use this transaction’s Isolation level in your production database, I would appreciate your comments about their performance on your servers. I have included here the complete script used in this example for your quick reference. ALTER DATABASE AdventureWorks SET ALLOW_SNAPSHOT_ISOLATION ON GO SELECT ModifiedDate FROM HumanResources.Shift GO -- Session 1 SET TRANSACTION ISOLATION LEVEL SNAPSHOT BEGIN TRAN UPDATE HumanResources.Shift SET ModifiedDate = GETDATE() GO -- Session 2 SET TRANSACTION ISOLATION LEVEL SNAPSHOT BEGIN TRAN SELECT ModifiedDate FROM HumanResources.Shift GO -- Session 1 COMMIT -- Session 2 SELECT ModifiedDate FROM HumanResources.Shift GO -- Session 2 COMMIT SELECT ModifiedDate FROM HumanResources.Shift GO Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Pinal Dave, SQL, SQL Authority, SQL Performance, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: Transaction Isolation

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  • jQuery Ajax Error Handling – How To Show Custom Error Messages

    - by schnieds
    So you want to make your error feedback nice for your users…Kind of an ironic statement isn’t it? We obviously want to avoid errors if at all possible in our applications, but when errors do occur then we want to provide some nice feedback to our users. The worst thing that can happen is to blow up a huge server exception page when something goes wrong or equally bad is not providing any feedback at all and leaving the user in the dark. Although I do not recommend displaying actual .NET Framework exception messages or stack traces to the user in most instances; they are usually not helpful to the user and can be a security concern.... [Read More]Aaron Schniederhttp://www.churchofficeonline.com

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  • Count Email Address Domains

    - by BRADINO
    A quick tidbit I came up with today to count email addresses in a mysql database table grouping them by domain. So say for example you have a large list of subscribers and you want to see the breakdown of people who use Hotmail, Yahoo, Gmail, etc. SELECT COUNT( SUBSTRING_INDEX( `email` , '@', -1 ) ) AS `count` , SUBSTRING_INDEX( `email` , '@', -1 ) AS `domain` FROM `subscribers` WHERE `email` != '' GROUP BY `domain` ORDER BY `count` DESC This sql statement assumes that the table is called 'subscribers' and the column containing the email addresses is 'email'. Change these two values to match your table name and email address column name. mysql count email mysql count domain mysql split email mysql split domain

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  • Optimizations employed by ORM's

    - by Kartoch
    I'm teaching JEE, especially JPA, Spring and Spring MVC. As I have not so much experience in large projects, it is difficult to know what to present to students about optimisation of ORM. At the present time, I present some classic optimisation tricks: prepared statements (most of ORM implicitely uses it by default) first and second-level caches "write first, optimize later" it is possible to switch off ORM and send SQL commands directly to the database for very frequent, specialized and costly requests Is there any other point the community see about other way to optimize ORM ? I'm especially interested by DAO patterns...

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  • LINQ for SQL Developers and DBA’s

    - by AtulThakor
    Firstly I’d just like to thank the guys who organise the SQL Server User Group (Martin/Tony/Chris) and for giving me the opportunity to speak at the recent event. Sorry about the slides taking so long but here they are along with some extra information. Firstly the demo’s were all done using LINQPad 4.0 which can be downloaded here: http://www.linqpad.net/ There are 2 versions 3.5/4.0 With 3.5 you should be able to replicate the problem I showed where a query using a parameter which is X characters long would create a different execution plan to a query which uses a parameter which is Y characters long, otherwise I would just use 4.0 The sample database used is AdventureWorksLT2008 which can be downloaded from here: http://msftdbprodsamples.codeplex.com/releases/view/37109 The scripts have been named so that you can select the appropriate way to run them i.e.: C# expression / C#statement, each script can be run individually be highlighting the query and clicking the play symbol or hitting F5. Scripts and Slides: http://sqlblogcasts.com/blogs/atulthakor/An%20Introduction%20to%20LINQ.zip Please don't hesitate in sending any questions via email/twitter, I’ll try my best to answer your questions! Thanks, Atul

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  • Parallelism in .NET – Part 8, PLINQ’s ForAll Method

    - by Reed
    Parallel LINQ extends LINQ to Objects, and is typically very similar.  However, as I previously discussed, there are some differences.  Although the standard way to handle simple Data Parellelism is via Parallel.ForEach, it’s possible to do the same thing via PLINQ. PLINQ adds a new method unavailable in standard LINQ which provides new functionality… LINQ is designed to provide a much simpler way of handling querying, including filtering, ordering, grouping, and many other benefits.  Reading the description in LINQ to Objects on MSDN, it becomes clear that the thinking behind LINQ deals with retrieval of data.  LINQ works by adding a functional programming style on top of .NET, allowing us to express filters in terms of predicate functions, for example. PLINQ is, generally, very similar.  Typically, when using PLINQ, we write declarative statements to filter a dataset or perform an aggregation.  However, PLINQ adds one new method, which provides a very different purpose: ForAll. The ForAll method is defined on ParallelEnumerable, and will work upon any ParallelQuery<T>.  Unlike the sequence operators in LINQ and PLINQ, ForAll is intended to cause side effects.  It does not filter a collection, but rather invokes an action on each element of the collection. At first glance, this seems like a bad idea.  For example, Eric Lippert clearly explained two philosophical objections to providing an IEnumerable<T>.ForEach extension method, one of which still applies when parallelized.  The sole purpose of this method is to cause side effects, and as such, I agree that the ForAll method “violates the functional programming principles that all the other sequence operators are based upon”, in exactly the same manner an IEnumerable<T>.ForEach extension method would violate these principles.  Eric Lippert’s second reason for disliking a ForEach extension method does not necessarily apply to ForAll – replacing ForAll with a call to Parallel.ForEach has the same closure semantics, so there is no loss there. Although ForAll may have philosophical issues, there is a pragmatic reason to include this method.  Without ForAll, we would take a fairly serious performance hit in many situations.  Often, we need to perform some filtering or grouping, then perform an action using the results of our filter.  Using a standard foreach statement to perform our action would avoid this philosophical issue: // Filter our collection var filteredItems = collection.AsParallel().Where( i => i.SomePredicate() ); // Now perform an action foreach (var item in filteredItems) { // These will now run serially item.DoSomething(); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } This would cause a loss in performance, since we lose any parallelism in place, and cause all of our actions to be run serially. We could easily use a Parallel.ForEach instead, which adds parallelism to the actions: // Filter our collection var filteredItems = collection.AsParallel().Where( i => i.SomePredicate() ); // Now perform an action once the filter completes Parallel.ForEach(filteredItems, item => { // These will now run in parallel item.DoSomething(); }); This is a noticeable improvement, since both our filtering and our actions run parallelized.  However, there is still a large bottleneck in place here.  The problem lies with my comment “perform an action once the filter completes”.  Here, we’re parallelizing the filter, then collecting all of the results, blocking until the filter completes.  Once the filtering of every element is completed, we then repartition the results of the filter, reschedule into multiple threads, and perform the action on each element.  By moving this into two separate statements, we potentially double our parallelization overhead, since we’re forcing the work to be partitioned and scheduled twice as many times. This is where the pragmatism comes into play.  By violating our functional principles, we gain the ability to avoid the overhead and cost of rescheduling the work: // Perform an action on the results of our filter collection .AsParallel() .Where( i => i.SomePredicate() ) .ForAll( i => i.DoSomething() ); The ability to avoid the scheduling overhead is a compelling reason to use ForAll.  This really goes back to one of the key points I discussed in data parallelism: Partition your problem in a way to place the most work possible into each task.  Here, this means leaving the statement attached to the expression, even though it causes side effects and is not standard usage for LINQ. This leads to my one guideline for using ForAll: The ForAll extension method should only be used to process the results of a parallel query, as returned by a PLINQ expression. Any other usage scenario should use Parallel.ForEach, instead.

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  • Best way to learn iphone audio queue services, step by step tutorial

    - by optician
    Hi Everyone, I'm trying to learn how to handle audio at a fairly low level with audio queue services. I have been progrmaing in memory managed languages for quite a while, and have just completed the c programing tutorial by vtc (2007). This has left me comfortable with the understanding of pointers and memory allocation, but the apple documention still leaves me wanting for a simpler implenation and explaination. Maybe I need to learn objective c and cocoa better. I have heard that this book is good. Cocoa(R) Programming for Mac(R) OS X (3rd Edition) Could someone suggest a learning path that is going to help me get an better understanding of working with audio and an iphone. I want to be able to play mp3 files back and also alter the pitch of them as they are playing. I am prepared that I may have to temporarily convert the mp3 files into pcm files to do things like that to them. Thanks everyone.

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