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• PostgreSQL 9: Does Vacuuming a table on the primary replicate on the mirror?

  - by Scott Herbert

  Running PostgreSQL 9.0.1, with streaming replication keeping one read-only mirror instance up to date. Auto-vaccuum is on on the primary, except for a few tables which are not vacuumed by the auto-vacuum daemon, in an effort to reduce business-hour IO. These tables are "materialised views". Each night at midnight, we run a vacuum across the database in order to clean up those tables that are excluded from the auto-vacuum. I'm wondering if that process replicates across to the mirror, or if I need to set up vacuum on the mirror as well?

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• SQL Server: Clutering by timestamp; pros/cons

  - by Ian Boyd

  i have a table in SQL Server, where i want inserts to be added to the end of the table (as opposed to a clustering key that would cause them to be inserted in the middle). This means i want the table clustered by some column that will constantly increase. This could be achieved by clustering on a datetime column: CREATE TABLE Things ( ... CreatedDate datetime DEFAULT getdate(), [timestamp] timestamp, CONSTRAINT [IX_Things] UNIQUE CLUSTERED (CreatedDate) ) But i can't guaranteed that two Things won't have the same time. So my requirements can't really be achieved by a datetime column. i could add a dummy identity int column, and cluster on that: CREATE TABLE Things ( ... RowID int IDENTITY(1,1), [timestamp] timestamp, CONSTRAINT [IX_Things] UNIQUE CLUSTERED (RowID) ) But you'll notice that my table already constains a timestamp column; a column which is guaranteed to be a monotonically increasing. This is exactly the characteristic i want for a candidate cluster key. So i cluster the table on the rowversion (aka timestamp) column: CREATE TABLE Things ( ... [timestamp] timestamp, CONSTRAINT [IX_Things] UNIQUE CLUSTERED (timestamp) ) Rather than adding a dummy identity int column (RowID) to ensure an order, i use what i already have. What i'm looking for are thoughts of why this is a bad idea; and what other ideas are better. Note: Community wiki, since the answers are subjective.

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• Oracle why does creating trigger fail when there is a field called timestamp?

  - by Omar Kooheji

  I've just wasted the past two hours of my life trying to create a table with an auto incrementing primary key bases on this tutorial, The tutorial is great the issue I've been encountering is that the Create Target fails if I have a column which is a timestamp and a table that is called timestamp in the same table... Why doesn't oracle flag this as being an issue when I create the table? Here is the Sequence of commands I enter: Creating the Table: CREATE TABLE myTable (id NUMBER PRIMARY KEY, field1 TIMESTAMP(6), timeStamp NUMBER, ); Creating the Sequence: CREATE SEQUENCE test_sequence START WITH 1 INCREMENT BY 1; Creating the trigger: CREATE OR REPLACE TRIGGER test_trigger BEFORE INSERT ON myTable REFERENCING NEW AS NEW FOR EACH ROW BEGIN SELECT test_sequence.nextval INTO :NEW.ID FROM dual; END; / Here is the error message I get: ORA-06552: PL/SQL: Compilation unit analysis terminated ORA-06553: PLS-320: the declaration of the type of this expression is incomplete or malformed Any combination that does not have the two lines with a the word "timestamp" in them works fine. I would have thought the syntax would be enough to differentiate between the keyword and a column name. As I've said I don't understand why the table is created fine but oracle falls over when I try to create the trigger... CLARIFICATION I know that the issue is that there is a column called timestamp which may or may not be a keyword. MY issue is why it barfed when I tried to create a trigger and not when I created the table, I would have at least expected a warning. That said having used Oracle for a few hours, it seems a lot less verbose in it's error reporting, Maybe just because I'm using the express version though. If this is a bug in Oracle how would one who doesn't have a support contract go about reporting it? I'm just playing around with the express version because I have to migrate some code from MySQL to Oracle.

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• Record Disappeared from Mysql Table, How Can I Find Out What Happened?

  - by Jascha

  I got the fire alarm phone call, AIM messages and email today from a client stating "The site is down!, WTF happened?!" Well, after a little digging, it turns out one of the records in a table had been wiped clean, but without removing the row itself. So, I had the representation of data, but a bunch of empty fields. (needless to day I need to write into my code a catch for this.) What my real question is, where can I figure out what happened? I've got access to phpmyadmin and that's about it. I found some access logs on in the root directory of my server, but that just tells me the client was in the admin area I built editing that record, I'd like to know specifically what they did that made all of the data go away. (what query was run etc...) is it possible without real server admin access? is there a neat little php to mysql class that returns data like this? Thanks in advance. -Jascha

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• Insert a datetime value with GetDate() function to a SQL server (2005) table?

  - by David.Chu.ca

  I am working (or fixing bugs) on an application which was developed in VS 2005 C#. The application saves data to a SQL server 2005. One of insert SQL statement tries to insert a time-stamp value to a field with GetDate() TSQL function as date time value. Insert into table1 (field1, ... fieldDt) values ('value1', ... GetDate()); The reason to use GetDate() function is that the SQL server may be at a remove site, and the date time may be in a difference time zone. Therefore, GetDate() will always get a date from the server. As the function can be verified in SQL Management Studio, this is what I get: SELECT GetDate(), LEN(GetDate()); -- 2010-06-10 14:04:48.293 19 One thing I realize is that the length is not up to the milliseconds, i.e., 19 is actually for '2010-06-10 14:04:48'. Anyway, the issue I have right now is that after the insert, the fieldDt actually has a date time value up to minutes, for example, '2010-06-10 14:04:00'. I am not sure why. I don't have permission to update or change the table with a trigger to update the field. My question is that how I can use a INSERT T-SQL to add a new row with a date time value ( SQL server's local date time) with a precision up to milliseconds?

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• Debugging apache seg fault with gdb

  - by Joyce Babu

  Apache on a production server of mine is seg faulting intermittently. I have enabled core dump option in apache configuration and have several dumped core files. Unfortunately, since it is a production server, apache or the loaded modules are not compiled with debug symbols. From what I understand, gdb cannot do much without debug symbols. Can I at least find out which module is causing the seg fault, without debug symbols? If so, how? Following is the output from a gdb backtrace (gdb) bt full #0 0xb7f1f832 in _dl_sysinfo_int80 () from /lib/ld-linux.so.2 No symbol table info available. #1 0xb7be82bc in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/libpthread.so.0 No symbol table info available. #2 0xb771652a in ?? () from /usr/local/apache/modules/mod_pagespeed.so No symbol table info available. #3 0xb75df576 in ?? () from /usr/local/apache/modules/mod_pagespeed.so No symbol table info available. #4 0xb7715c20 in ?? () from /usr/local/apache/modules/mod_pagespeed.so No symbol table info available. #5 0xb7be4a49 in start_thread () from /lib/libpthread.so.0 No symbol table info available. #6 0xb7b2a63e in clone () from /lib/libc.so.6 No symbol table info available. Does this mean that /lib/ld-linux.so.2 is causing the seg fault?

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• PostgreSQL, Foreign Keys, Insert speed & Django

  - by Miles

  A few days ago, I ran into an unexpected performance problem with a pretty standard Django setup. For an upcoming feature, we have to regenerate a table hourly, containing about 100k rows of data, 9M on the disk, 10M indexes according to pgAdmin. The problem is that inserting them by whatever method literally takes ages, up to 3 minutes of 100% disk busy time. That's not something you want on a production site. It doesn't matter if the inserts were in a transaction, issued via plain insert, multi-row insert, COPY FROM or even INSERT INTO t1 SELECT * FROM t2. After noticing this isn't Django's fault, I followed a trial and error route, and hey, the problem disappeared after dropping all foreign keys! Instead of 3 minutes, the INSERT INTO SELECT FROM took less than a second to execute, which isn't too surprising for a table <= 20M on the disk. What is weird is that PostgreSQL manages to slow down inserts by 180x just by using 3 foreign keys. Oh, disk activity was pure writing, as everything is cached in RAM; only writes go to the disks. It looks like PostgreSQL is working very hard to touch every row in the referred tables, as 3MB/sec * 180s is way more data than the 20MB this new table takes on disk. No WAL for the 180s case, I was testing in psql directly, in Django, add ~50% overhead for WAL logging. Tried @commit_on_success, same slowness, I had even implemented multi row insert and COPY FROM with psycopg2. That's another weird thing, how can 10M worth of inserts generate 10x 16M log segments? Table layout: id serial primary, a bunch of int32, 3 foreign keys to small table, 198 rows, 16k on disk large table, 1.2M rows, 59 data + 89 index MB on disk large table, 2.2M rows, 198 + 210MB So, am I doomed to either drop the foreign keys manually or use the table in a very un-Django way by defining saving bla_id x3 and skip using models.ForeignKey? I'd love to hear about some magical antidote / pg setting to fix this.

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• Clustered index - multi-part vs single-part index and effects of inserts/deletes

  - by Anssssss

  This question is about what happens with the reorganizing of data in a clustered index when an insert is done. I assume that it should be more expensive to do inserts on a table which has a clustered index than one that does not because reorganizing the data in a clustered index involves changing the physical layout of the data on the disk. I'm not sure how to phrase my question except through an example I came across at work. Assume there is a table (Junk) and there are two queries that are done on the table, the first query searches by Name and the second query searches by Name and Something. As I'm working on the database I discovered that the table has been created with two indexes, one to support each query, like so: --drop table Junk1 CREATE TABLE Junk1 ( Name char(5), Something char(5), WhoCares int ) CREATE CLUSTERED INDEX IX_Name ON Junk1 ( Name ) CREATE NONCLUSTERED INDEX IX_Name_Something ON Junk1 ( Name, Something ) Now when I looked at the two indexes, it seems that IX_Name is redundant since IX_Name_Something can be used by any query that desires to search by Name. So I would eliminate IX_Name and make IX_Name_Something the clustered index instead: --drop table Junk2 CREATE TABLE Junk2 ( Name char(5), Something char(5), WhoCares int ) CREATE CLUSTERED INDEX IX_Name_Something ON Junk2 ( Name, Something ) Someone suggested that the first indexing scheme should be kept since it would result in more efficient inserts/deletes (assume that there is no need to worry about updates for Name and Something). Would that make sense? I think the second indexing method would be better since it means one less index needs to be maintained. I would appreciate any insight into this specific example or directing me to more info on maintenance of clustered indexes.

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• PHP / Zend Framework: Force prepend table name to column name in result array?

  - by Brian Lacy

  I am using Zend_Db_Select currently to retrieve hierarchical data from several joined tables. I need to be able to convert this easily into an array. Short of using a switch statement and listing out all the columns individually in order to sort the data, my thought was that if I could get the table names auto-prepended to the keys in the result array, that would solve my problem. So considering the following (assembled) SQL: SELECT user.*, contact.* FROM user INNER JOIN contact ON contact.user_id = user.user_id I would normally get a result array like this: [username] => 'bob', [contact_id] => 5, [user_id] => 2, [firstname] => 'bob', [lastname] => 'larsen' But instead I want this: [user.user_id] => 2, [user.username] => 'bob', [contact.contact_id] => 5, [contact.firstname] => 'bob', [contact.lastname] => 'larsen' Does anyone have an idea how to achieve this? Thanks!

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• Mysql return value as 0 in the fetch result.

  - by Karthik

  I have this two tables, -- -- Table structure for table `t1` -- CREATE TABLE `t1` ( `pid` varchar(20) collate latin1_general_ci NOT NULL, `pname` varchar(20) collate latin1_general_ci NOT NULL ) ENGINE=MyISAM DEFAULT CHARSET=latin1 COLLATE=latin1_general_ci; -- -- Dumping data for table `t1` -- INSERT INTO `t1` VALUES ('p1', 'pro1'); INSERT INTO `t1` VALUES ('p2', 'pro2'); -- -------------------------------------------------------- -- -- Table structure for table `t2` -- CREATE TABLE `t2` ( `pid` varchar(20) collate latin1_general_ci NOT NULL, `year` int(6) NOT NULL, `price` int(3) NOT NULL ) ENGINE=MyISAM DEFAULT CHARSET=latin1 COLLATE=latin1_general_ci; -- -- Dumping data for table `t2` -- INSERT INTO `t2` VALUES ('p1', 2009, 50); INSERT INTO `t2` VALUES ('p1', 2010, 60); INSERT INTO `t2` VALUES ('p3', 2007, 200); INSERT INTO `t2` VALUES ('p4', 2008, 501); my query is, SELECT * FROM `t1` LEFT JOIN `t2` ON t1.pid = t2.pid Getting the result, pid pname pid year price p1 pro1 p1 2009 50 p1 pro1 p1 2010 60 p2 pro2 NULL NULL NULL My question is, i want to get the price value is 0 instead of NULL. How can i write the query to getting the price value is 0. Thanks in advance for help.

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• How do I return a nested table from an oracle function using Java?

  - by Benny

  I have the following type declaration and Oracle function: CREATE OR REPLACE TYPE var_outcomes_results IS TABLE OF VARCHAR2(80); CREATE OR REPLACE FUNCTION getValuesAbove(in_nodeID IN table1.KEY_SL%TYPE, in_variable IN VARCHAR2) RETURN var_outcomes_results IS currentID table1.KEY_SL%TYPE; results var_outcomes_results; currentIndex integer := 0; BEGIN currentID := in_nodeID; WHILE currentID != null LOOP FOR outcomeRecord IN (select distinct a.PARENT, b.NAME, c.OUTCOME from table1 a left outer join table2 b on a.KEY_SL = b.KEY_SL left outer join table3 c on b.VAR_ID = c.VAR_ID where a.KEY_SL = currentID) LOOP currentID := outcomeRecord.PARENT; IF lower(outcomeRecord.NAME) = lower(in_variable) AND outcomeRecord.OUTCOME != null THEN currentIndex := currentIndex + 1; results(currentIndex) := outcomeRecord.OUTCOME; END IF; END LOOP; END LOOP; RETURN results; END; I have the following Java function: public List<Object> getAboveValues(String variable, Integer nodeID) { Connection connection = null; CallableStatement callableStatement = null; try { connection = dataSource.getConnection(); callableStatement = connection.prepareCall("begin ? := getValuesAbove(?,?); end;"); callableStatement.registerOutParameter(1, OracleTypes.ARRAY); callableStatement.setInt(2, nodeID); callableStatement.setString(3, variable); callableStatement.execute(); System.out.println(callableStatement.getObject(1)); } catch( SQLException e ) { logger.error("An Exception was thrown in getAboveValues: " + e); } finally { closeDataResources(callableStatement, connection); } } However, when I execute the function, I get the following error message: "ORA-03115: unsupported network datatype or representation" What am I doing wrong? Any ideas/suggestions would be appreciated. Thanks, B.J.

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• Global Temporary Table "On commit delete rows" functionality discrepancy.

  - by TomatoSandwich

  I have a global temporary table. I called my GTT, for that was it's initials. My GTT never hurt anyone, and did everything I bade of it. I asked my GTT to delete rows on commit. This is a valid function in the creation script of my GTT in oracle. I wanted to be able to have different users see GTT with their own data, and not the data of other people's sessions. 'Delete rows on commit' worked perfectly in our test environment. GTT and I were happy. But then, I deployed GTT as part of an update to functionality to a client's database. The database doesn't like to play well with GTT. GTT called me up all upset and worried, because it wasn't holding any data any more, and didn't know why. GTT told me that if someone did: insert into my_GTT (description) values ('Happy happy joy joy') he would sing-song back: 1 row inserted. However, if the same person tried select * from my_GTT; GTT didn't know what to do, and he replied 0 rows returned. GTT was upset that he didn't know what his playmate had inserted. Please, Stackoverflow, why would GTT forget what was placed into him? He can remember perfectly well at home, but out in the cold harsh world, he just gets so scared. :(

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• How to avoid multiple, unused has_many associations when using multiple models for the same entity (

  - by mikep

  Hello, I'm looking for a nice, Ruby/Rails-esque solution for something. I'm trying to split up some data using multiple tables, rather than just using one gigantic table. My reasoning is pretty much to try and avoid the performance drop that would come with having a big table. So, rather than have one table called books, I have multiple tables: books1, books2, books3, etc. (I know that I could use a partition, but, for now, I've decided to go the 'multiple tables' route.) Each user has their books placed into a specific table. The actual book table is chosen when the user is created, and all of their books go into the same table. The goal is to try and keep each table pretty much even -- but that's a different issue. One thing I don't particularly want to have is a bunch of unused associations in the User class. Right now, it looks like I'd have to do the following: class User < ActiveRecord::Base has_many :books1, :books2, :books3, :books4, :books5 end class Books1 < ActiveRecord::Base belongs_to :user end class Books2 < ActiveRecord::Base belongs_to :user end First off, for each specific user, only one of the book tables would be usable/applicable, since all of a user's books are stored in the same table. So, only one of the associations would be in use at any time and any other has_many :bookX association that was loaded would be a waste. I don't really know Ruby/Rails does internally with all of those has_many associations though, so maybe it's not so bad. But right now I'm thinking that it's really wasteful, and that there may just be a better, more efficient way of doing this. Is there's some sort of special Ruby/Rails methodology that could be applied here to avoid having to have all of those has_many associations? Also, does anyone have any advice on how to abstract the fact that there's multiple book tables behind a single books model/class?

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• How can you trigger the viewWillAppear of a UITableView AFTER its UINavigationController?

  - by Troy Sartain

  I have a situation where I use a tab bar set up but with nav bar controllers on a couple tabs. Those tabs have table views on them. Everything works great, I can pick a tab and get a different table in a nav bar structure. The other tabs are non-nav controllers. Fine. I want to use the same table view controller and even the same detail screen since they are essentially the same format. I have two-dimensional arrays and a couple of vars tracking which tab and which table row so when I get to the detail it's all good. Now to the problem. It all seems to work just fine until I return to a tab that has already been visited. At that point, I do indeed get a viewWillAppear for both the view controller of that specific tab and the table view controller. However, I get the table view one first! It doesn't know which tab was tapped on; the other one does but that's too late to dynamically change the table! Any suggestions? Am I being too greedy about code duplication? I mean I could just make separate controllers for for each table view and then separate detail view controllers but I thought I had a good solution.

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• using dummy row with NOT NULL to solve DEFAULT NULL

  - by Tony38

  I know having DEFAULT NULLS is not a good practice but I have many optional lookup values which are FK in the system so to solve this issue here is what i am doing: I use NOT NULL for every FK / lookup colunms. I have the first row in every lookup table which is PK id = 1 as a dummy row with just "none" in all the columns. This way I can use NOT NULL in my schema and if needed reference to the none row values PK =1 for FKs which do not have any lookup value. Is this a good design or any other work arounds? EDIT: I have: Neighborhood table Postal table. Every neighborhood has a city, so the FK can be NOT NULL. But not every postal code belongs to a neighborhood. Some do, some don't depending on the country. So if i use NOT NULL for the FK between postal and neighborhood then I will be screwed as there has to be some value entered. So what i am doing in essence is: have a row in every table to be a dummy row just to link the FKs. This way row one in neighborhood table will be: n_id = 1 name =none etc... In postal table I can have: postal_code = 3456A3 FK (city) = Moscow FK (neighborhood_id)=1 as a NOT NULL. If I don't have a dummy row in the neighborhood lookup table then I have to declare FK (neighborhood_id) as a Default null column and store blanks in the table. This is an example but there is a huge number of values which will have blanks then in many tables.

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• How to maintain an ordered table with Core Data (or SQL) with insertions/deletions?

  - by Jean-Denis Muys

  This question is in the context of Core Data, but if I am not mistaken, it applies equally well to a more general SQL case. I want to maintain an ordered table using Core Data, with the possibility for the user to: reorder rows insert new lines anywhere delete any existing line What's the best data model to do that? I can see two ways: 1) Model it as an array: I add an int position property to my entity 2) Model it as a linked list: I add two one-to-one relations, next and previous from my entity to itself 1) makes it easy to sort, but painful to insert or delete as you then have to update the position of all objects that come after 2) makes it easy to insert or delete, but very difficult to sort. In fact, I don't think I know how to express a Sort Descriptor (SQL ORDER BY clause) for that case. Now I can imagine a variation on 1): 3) add an int ordering property to the entity, but instead of having it count one-by-one, have it count 100 by 100 (for example). Then inserting is as simple as finding any number between the ordering of the previous and next existing objects. The expensive renumbering only has to occur when the 100 holes have been filled. Making that property a float rather than an int makes it even better: it's almost always possible to find a new float midway between two floats. Am I on the right track with solution 3), or is there something smarter?

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• SQL Server - Complex Dynamic Pivot columns

  - by user972255

  I have two tables "Controls" and "ControlChilds" Parent Table Structure: Create table Controls( ProjectID Varchar(20) NOT NULL, ControlID INT NOT NULL, ControlCode Varchar(2) NOT NULL, ControlPoint Decimal NULL, ControlScore Decimal NULL, ControlValue Varchar(50) ) Sample Data ProjectID | ControlID | ControlCode | ControlPoint | ControlScore | ControlValue P001 1 A 30.44 65 Invalid P001 2 C 45.30 85 Valid Child Table Structure: Create table ControlChilds( ControlID INT NOT NULL, ControlChildID INT NOT NULL, ControlChildValue Varchar(200) NULL ) Sample Data ControlID | ControlChildID | ControlChildValue 1 100 Yes 1 101 No 1 102 NA 1 103 Others 2 104 Yes 2 105 SomeValue Output should be in a single row for a given ProjectID with all its Control values first & followed by child control values (based on the ControlCode (i.e.) ControlCode_Child (1, 2, 3...) and it should look like this Also, I tried this PIVOT query and I am able to get the ChildControls table values but I dont know how to get the Controls table values. DECLARE @cols AS NVARCHAR(MAX); DECLARE @query AS NVARCHAR(MAX); select @cols = STUFF((SELECT distinct ',' + QUOTENAME(ControlCode + '_Child' + CAST(ROW_NUMBER() over(PARTITION BY ControlCode ORDER BY ControlChildID) AS Varchar(25))) FROM Controls C INNER JOIN ControlChilds CC ON C.ControlID = CC.ControlID FOR XML PATH(''), TYPE ).value('.', 'NVARCHAR(MAX)') , 1, 1, ''); SELECT @query ='SELECT * FROM ( SELECT (ControlCode + ''_Child'' + CAST(ROW_NUMBER() over(PARTITION BY ControlCode ORDER BY ControlChildID) AS Varchar(25))) As Code, ControlChildValue FROM Controls AS C INNER JOIN ControlChilds AS CC ON C.ControlID = CC.ControlID ) AS t PIVOT ( MAX(ControlChildValue) FOR Code IN( ' + @cols + ' )' + ' ) AS p ; '; execute(@query); Output I am getting: Can anyone please help me on how to get the Controls table values in front of each ControlChilds table values?

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• C: Random Number Generation - What (If Anything) Is Wrong With This

  - by raoulcousins

  For a simple simulation in C, I need to generate exponential random variables. I remember reading somewhere (but I can't find it now, and I don't remember why) that using the rand() function to generate random integers in a fixed range would generate non-uniformly distributed integers. Because of this, I'm wondering if this code might have a similar problem: //generate u ~ U[0,1] u = ( (double)rand() / ((double)(RAND_MAX)); //inverse of exponential CDF to get exponential random variable expon = -log(1-u) * mean; Thank you!

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• jquery nextUntil has element

  - by Mark

  jquery nextUntil has element I have a bunch of elements like this: <div></div> <span></span> <table></table> <div></div> <span></span> <div></div> I need to check whether or not there's a table element in between the divs, and if so do something. $('div').each(function () { if ($(this).nextUntil('div').include('table')) { $(this).addClass('got-a-table'); } } Something like this? I know that there's no include method, is there something that can get me what I need? Thanks. Result should be like this: <div class='got-a-table'></div> <span></span> <table></table> <div></div> <span></span> <div></div>

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• database structure

  - by jindalsyogesh

  I have a table named ActivityRecording. This table currently has 500,000 records. I need to add a lot of new inputs that relates to activityrecording table. The relation of activityrecording with these new input fields is 1 to 0,1. So, what's going to happen on screen is when user fills the ActivityRecording data, he will then be taken to a new page and this page will show a form based on the user's input (from a dropdown named service) in activityrecording. There will 6 different kinds of form (each form will have 7-8 inputs which includes textareas of size 5kb, textboxes and checkboxes). So, for one activityrecording user will fill one out of 6 forms. There are two ways I know (there could be more), I can design the data structure: Add all the inputs from all these 6 forms into the activityrecording table. So, columns belonging to 5 of these forms will be null in this table, only columns belonging to one of the forms will have values The other way would be add 6 new tables (one for each form) and add 6 foreign key columns to activityrecording table. So, out of 6 foreign keys, 5 will be null and one will actually point to a table Which approach is a better data structure design? Please take into consideration that number of rows in this table are 500,000 and are expected to grow at a faster rate now.

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• Can I change a MySQL table back and forth between InnoDB and MyISAM without any problems?

  - by Daniel Magliola

  I have a site with a decently big database, 3Gb in size, a couple of tables with a dozen million records. It's currently 100% on MyISAM, and I have the feeling that the server is going slower than it should because of too much locking, so I'd like to try going to InnoDB and see if that makes things better. However, I need to do that directly in production, because obviously without load this doesn't make any difference. However, I'm a bit worried about this, because InnoDB actually has potential to be slower, so the question is: If I convert all tables to InnoDB and it turns out i'm worse off than before, can I go back to MyISAM without losing anything? Can you think of any problems I might encounter? (For example, I know that InnoDB stores all data in ONE big file that only gets bigger, can this be a problem?) Thank you very much Daniel

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• Joining Tables Based on Foreign Keys

  - by maestrojed

  I have a table that has a lot of fields that are foreign keys referencing a related table. I am writing a script in PHP that will do the db queries. When I query this table for its data I need to know the values associated with these keys not the key. How do most people go about this? A 101 way to do this would be to query this table for its data including the foreign keys and then query the related tables to get each key's value. This could be a lot of queries (~10). Question 1: I think I could write 1 query with a bunch of joins. Would that be better? This approach also requires the querying script to know which table fields are foreign keys. Since I have many tables like this but all with different fields, this means writing nice generic functions is hard. MySQL InnoDB tables allow for foreign constraints. I know the database has these set up correctly. Question 2: What about the idea of querying the table and identifying what the constraints are and then matching them up using whatever process I decide on from Question 1. I like this idea but never see it being used in code. Makes me think its not a good idea for some reason. I would use something like SHOW CREATE TABLE tbl_name; to find what constraints/relationships exist for that table. Thank you for any suggestions or advice.

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• Will this class cause memory leaks, and does it need a dispose method? (asp.net vb)

  - by Phil

  Here is the class to export a gridview to an excel sheet: Imports System Imports System.Data Imports System.Configuration Imports System.IO Imports System.Web Imports System.Web.Security Imports System.Web.UI Imports System.Web.UI.WebControls Imports System.Web.UI.WebControls.WebParts Imports System.Web.UI.HtmlControls Namespace ExcelExport Public NotInheritable Class GVExportUtil Private Sub New() End Sub Public Shared Sub Export(ByVal fileName As String, ByVal gv As GridView) HttpContext.Current.Response.Clear() HttpContext.Current.Response.AddHeader("content-disposition", String.Format("attachment; filename={0}", fileName)) HttpContext.Current.Response.ContentType = "application/ms-excel" Dim sw As StringWriter = New StringWriter Dim htw As HtmlTextWriter = New HtmlTextWriter(sw) Dim table As Table = New Table table.GridLines = GridLines.Vertical If (Not (gv.HeaderRow) Is Nothing) Then GVExportUtil.PrepareControlForExport(gv.HeaderRow) table.Rows.Add(gv.HeaderRow) End If For Each row As GridViewRow In gv.Rows GVExportUtil.PrepareControlForExport(row) table.Rows.Add(row) Next If (Not (gv.FooterRow) Is Nothing) Then GVExportUtil.PrepareControlForExport(gv.FooterRow) table.Rows.Add(gv.FooterRow) End If table.RenderControl(htw) HttpContext.Current.Response.Write(sw.ToString) HttpContext.Current.Response.End() End Sub Private Shared Sub PrepareControlForExport(ByVal control As Control) Dim i As Integer = 0 Do While (i < control.Controls.Count) Dim current As Control = control.Controls(i) If (TypeOf current Is LinkButton) Then control.Controls.Remove(current) control.Controls.AddAt(i, New LiteralControl(CType(current, LinkButton).Text)) ElseIf (TypeOf current Is ImageButton) Then control.Controls.Remove(current) control.Controls.AddAt(i, New LiteralControl(CType(current, ImageButton).AlternateText)) ElseIf (TypeOf current Is HyperLink) Then control.Controls.Remove(current) control.Controls.AddAt(i, New LiteralControl(CType(current, HyperLink).Text)) ElseIf (TypeOf current Is DropDownList) Then control.Controls.Remove(current) control.Controls.AddAt(i, New LiteralControl(CType(current, DropDownList).SelectedItem.Text)) ElseIf (TypeOf current Is CheckBox) Then control.Controls.Remove(current) control.Controls.AddAt(i, New LiteralControl(CType(current, CheckBox).Checked)) End If If current.HasControls Then GVExportUtil.PrepareControlForExport(current) End If i = (i + 1) Loop End Sub End Class End Namespace Will this class cause memory leaks? And does anything here need to be disposed of? The code is working but I am getting frequent crashes of the app pool when it is in use. Thanks.

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• how do i automatically add a new route to the routing table?

  - by Robbie Mckennie

  I'm looking at linking two networks with a long range Ethernet bridge. I know I can connect my two networks with a router, but my problem is how will my computers know where to send packets if I don't add the route manually? I COULD add them manually, but it seems like a hassle. I have very very limited knowledge of RIP (I know it has something to do with routing), but I don't know how to use it. edit: My vision for the network would be the 2 networks (which are currently independent home networks), connected by a microwave Ethernet link. I assumed i'd need a router on one end of the bridge, to handle communication between the 2 networks.

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• Codeigniter php activerecord orm limit and offset

  - by user2167174

  I am a bit stuck with this problem I have in phpactiverecord. What I am trying to do is a pagination so I need to limit and offset the query results. I am accessing all of the user posts like so: $user-post; How can I query this to limit and offset the results? Thanx in advance. Code: public function office() { if (!$this->session->userdata('username')) { redirect(base_url()); } $data = array(); $data['posts'] = []; $user = User::find('first', array('id' => $this->session->userdata('id'))); if ($user != null) { if ($user->post != null) { foreach ($user->post as $post) { $posts = array($post->name, $post->description, $post->date,'<a href="'.base_url().'Posts/edit/'.$post->id.'">Edit</a> <br /><a href="'.base_url().'Posts/delete/'.$post->id.'">Delete</a>'); array_push($data['posts'], $posts); } $this->table->set_heading('Name', 'Description', 'Date', '<a href="'.base_url().'Posts/create">+Add</a>'); $tmpl = array('table_open' => '<table class="table table-stripped table-bordered user-posts">'); $this->table->set_template($tmpl); $data['table'] = $this->table->generate($data['posts']); } $this->load->view('template/header.php'); $this->load->view('Users/office.php', $data); $this->load->view('template/footer.php'); } else { redirect(base_url()); } }

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