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  • Problem creating a database with PHP PDO

    - by Leandro Alonso
    Hello guys, I'm having a problem with a SQL query in my PHP Application. When the user access it for the first time, the app executes this query to create all the database: CREATE TABLE `databases` ( `id` bigint(20) NOT NULL auto_increment, `driver` varchar(45) NOT NULL, `server` text NOT NULL, `user` text NOT NULL, `password` text NOT NULL, `database` varchar(200) NOT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=2 ; -- -------------------------------------------------------- -- -- Table structure for table `modules` -- CREATE TABLE `modules` ( `id` bigint(20) unsigned NOT NULL auto_increment, `title` varchar(100) NOT NULL, `type` varchar(150) NOT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=29 ; -- -------------------------------------------------------- -- -- Table structure for table `modules_data` -- CREATE TABLE `modules_data` ( `id` bigint(20) NOT NULL auto_increment, `module_id` bigint(20) unsigned NOT NULL, `key` varchar(150) NOT NULL, `value` tinytext, PRIMARY KEY (`id`), KEY `fk_modules_data_modules` (`module_id`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=184 ; -- -------------------------------------------------------- -- -- Table structure for table `modules_position` -- CREATE TABLE `modules_position` ( `user_id` bigint(20) unsigned NOT NULL, `tab_id` bigint(20) unsigned NOT NULL, `module_id` bigint(20) unsigned NOT NULL, `column` smallint(1) default NULL, `line` smallint(1) default NULL, PRIMARY KEY (`user_id`,`tab_id`,`module_id`), KEY `fk_modules_order_users` (`user_id`), KEY `fk_modules_order_tabs` (`tab_id`), KEY `fk_modules_order_modules` (`module_id`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1; -- -------------------------------------------------------- -- -- Table structure for table `tabs` -- CREATE TABLE `tabs` ( `id` bigint(20) unsigned NOT NULL auto_increment, `title` varchar(60) NOT NULL, `columns` smallint(1) NOT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=12 ; -- -------------------------------------------------------- -- -- Table structure for table `tabs_has_modules` -- CREATE TABLE `tabs_has_modules` ( `tab_id` bigint(20) unsigned NOT NULL, `module_id` bigint(20) unsigned NOT NULL, PRIMARY KEY (`tab_id`,`module_id`), KEY `fk_tabs_has_modules_tabs` (`tab_id`), KEY `fk_tabs_has_modules_modules` (`module_id`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1; -- -------------------------------------------------------- -- -- Table structure for table `users` -- CREATE TABLE `users` ( `id` bigint(20) unsigned NOT NULL auto_increment, `login` varchar(60) NOT NULL, `password` varchar(64) NOT NULL, `email` varchar(100) NOT NULL, `name` varchar(250) default NULL, `user_level` bigint(20) unsigned NOT NULL, PRIMARY KEY (`id`), KEY `fk_users_user_levels` (`user_level`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=4 ; -- -------------------------------------------------------- -- -- Table structure for table `users_has_tabs` -- CREATE TABLE `users_has_tabs` ( `user_id` bigint(20) unsigned NOT NULL, `tab_id` bigint(20) unsigned NOT NULL, `order` smallint(2) NOT NULL, `columns_width` varchar(255) default NULL, PRIMARY KEY (`user_id`,`tab_id`), KEY `fk_users_has_tabs_users` (`user_id`), KEY `fk_users_has_tabs_tabs` (`tab_id`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1; -- -------------------------------------------------------- -- -- Table structure for table `user_levels` -- CREATE TABLE `user_levels` ( `id` bigint(20) unsigned NOT NULL auto_increment, `level` smallint(2) NOT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=3 ; -- -------------------------------------------------------- -- -- Table structure for table `user_meta` -- CREATE TABLE `user_meta` ( `id` bigint(20) unsigned NOT NULL auto_increment, `user_id` bigint(20) unsigned default NULL, `key` varchar(150) NOT NULL, `value` longtext NOT NULL, PRIMARY KEY (`id`), KEY `fk_user_meta_users` (`user_id`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=4 ; -- -- Constraints for dumped tables -- -- -- Constraints for table `modules_data` -- ALTER TABLE `modules_data` ADD CONSTRAINT `fk_modules_data_modules` FOREIGN KEY (`module_id`) REFERENCES `modules` (`id`) ON DELETE CASCADE ON UPDATE NO ACTION; -- -- Constraints for table `modules_position` -- ALTER TABLE `modules_position` ADD CONSTRAINT `fk_modules_order_modules` FOREIGN KEY (`module_id`) REFERENCES `modules` (`id`) ON DELETE CASCADE ON UPDATE NO ACTION, ADD CONSTRAINT `fk_modules_order_tabs` FOREIGN KEY (`tab_id`) REFERENCES `tabs` (`id`) ON DELETE CASCADE ON UPDATE NO ACTION, ADD CONSTRAINT `fk_modules_order_users` FOREIGN KEY (`user_id`) REFERENCES `users` (`id`) ON DELETE CASCADE ON UPDATE NO ACTION; -- -- Constraints for table `users` -- ALTER TABLE `users` ADD CONSTRAINT `fk_users_user_levels` FOREIGN KEY (`user_level`) REFERENCES `user_levels` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION; -- -- Constraints for table `user_meta` -- ALTER TABLE `user_meta` ADD CONSTRAINT `fk_user_meta_users` FOREIGN KEY (`user_id`) REFERENCES `users` (`id`) ON DELETE CASCADE ON UPDATE NO ACTION; INSERT INTO `user_levels` VALUES(1, 10); INSERT INTO `user_levels` VALUES(2, 1); INSERT INTO `users` VALUES(1, 'admin', 'password', '[email protected]', NULL, 1); INSERT INTO `user_meta` VALUES (NULL, 1, 'last_tab', 1); In some environments i get this error: SQLSTATE[HY000]: General error: 1005 Can't create table 'dms.databases' (errno: 150) I tried everything that I could find on Google but nothing works. The strange part is that if I run this query in PhpMyAdmin he creates my database, without any error.

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  • Boost::thread mutex issue: Try to lock, access violation

    - by user1419305
    I am currently learning how to multithread with c++, and for that im using boost::thread. I'm using it for a simple gameengine, running three threads. Two of the threads are reading and writing to the same variables, which are stored inside something i call PrimitiveObjects, basicly balls, plates, boxes etc. But i cant really get it to work, i think the problem is that the two threads are trying to access the same memorylocation at the same time, i have tried to avoid this using mutex locks, but for now im having no luck, this works some times, but if i spam it, i end up with this exception: First-chance exception at 0x00cbfef9 in TTTTT.exe: 0xC0000005: Access violation reading location 0xdddddded. Unhandled exception at 0x77d315de in TTTTT.exe: 0xC0000005: Access violation reading location 0xdddddded. These are the functions inside the object that im using for this, and the debugger is also blaming them for the exception. void PrimitiveObj::setPos(glm::vec3 in){ boost::mutex mDisposingMutex; boost::try_mutex::scoped_try_lock lock(mDisposingMutex); if ( lock) { position = in; boost::try_mutex::scoped_try_lock unlock(mDisposingMutex); } } glm::vec3 PrimitiveObj::getPos(){ boost::mutex myMutex; boost::try_mutex::scoped_try_lock lock(myMutex); if ( lock) { glm::vec3 curPos = position; boost::try_mutex::scoped_try_lock unlock(myMutex); return curPos; } return glm::vec3(0,0,0); } Any ideas?

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  • WCF Transaction Scope SQL insert table lock

    - by lihnid
    Hi All, I have two services talking to two different Data-stores (i.e SQL). I am using transactionscope: eg: using(TransactionScope scope = new TransactionScope()) { service1.InsertUser(user);//Insert to SQL Service 1 table User service2.SavePayment(payment);//Save payment SQL Service 2 table payment scope.Complete(); } Service1 is locking the table (User) until the transaction is completed making subsequent transactions with that table sequential. Is there a way to overcome the lock, so can have more than one concurrent calls to the SQL service1 table while the above code is executing? I would appreciate any input. Thanks in Advance. Lihnid

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  • How the number of indexes built on a table can impact performances?

    - by Davide Mauri
    We all know that putting too many indexes (I’m talking of non-clustered index only, of course) on table may produce performance problems due to the overhead that each index bring to all insert/update/delete operations on that table. But how much? I mean, we all agree – I think – that, generally speaking, having many indexes on a table is “bad”. But how bad it can be? How much the performance will degrade? And on a concurrent system how much this situation can also hurts SELECT performances? If SQL Server take more time to update a row on a table due to the amount of indexes it also has to update, this also means that locks will be held for more time, slowing down the perceived performance of all queries involved. I was quite curious to measure this, also because when teaching it’s by far more impressive and effective to show to attended a chart with the measured impact, so that they can really “feel” what it means! To do the tests, I’ve create a script that creates a table (that has a clustered index on the primary key which is an identity column) , loads 1000 rows into the table (inserting 1000 row using only one insert, instead of issuing 1000 insert of one row, in order to minimize the overhead needed to handle the transaction, that would have otherwise ), and measures the time taken to do it. The process is then repeated 16 times, each time adding a new index on the table, using columns from table in a round-robin fashion. Test are done against different row sizes, so that it’s possible to check if performance changes depending on row size. The result are interesting, although expected. This is the chart showing how much time it takes to insert 1000 on a table that has from 0 to 16 non-clustered indexes. Each test has been run 20 times in order to have an average value. The value has been cleaned from outliers value due to unpredictable performance fluctuations due to machine activity. The test shows that in a  table with a row size of 80 bytes, 1000 rows can be inserted in 9,05 msec if no indexes are present on the table, and the value grows up to 88 (!!!) msec when you have 16 indexes on it This means a impact on performance of 975%. That’s *huge*! Now, what happens if we have a bigger row size? Say that we have a table with a row size of 1520 byte. Here’s the data, from 0 to 16 indexes on that table: In this case we need near 22 msec to insert 1000 in a table with no indexes, but we need more that 500msec if the table has 16 active indexes! Now we’re talking of a 2410% impact on performance! Now we can have a tangible idea of what’s the impact of having (too?) many indexes on a table and also how the size of a row also impact performances. That’s why the golden rule of OLTP databases “few indexes, but good” is so true! (And in fact last week I saw a database with tables with 1700bytes row size and 23 (!!!) indexes on them!) This also means that a too heavy denormalization is really not a good idea (we’re always talking about OLTP systems, keep it in mind), since the performance get worse with the increase of the row size. So, be careful out there, and keep in mind the “equilibrium” is the key world of a database professional: equilibrium between read and write performance, between normalization and denormalization, between to few and too may indexes. PS Tests are done on a VMWare Workstation 7 VM with 2 CPU and 4 GB of Memory. Host machine is a Dell Precsioni M6500 with i7 Extreme X920 Quad-Core HT 2.0Ghz and 16Gb of RAM. Database is stored on a SSD Intel X-25E Drive, Simple Recovery Model, running on SQL Server 2008 R2. If you also want to to tests on your own, you can download the test script here: Open TestIndexPerformance.sql

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  • SQL Server 2008 Dead lock issue

    - by user173552
    I got into a deadlock issue where I am struggling find the root-cause...The Deadlock graph suggests that an UPDATE statement became the victim over a SELECT statement... What puzzles me is that the UPDATE statement is trying to acquire an index on some other table that is never referred in update statement... This is how my UPDATE statement looks like... UPDATE Table set col1 = @P1 where col2 = @P2 This statement acquired a X lock on the col2 index, but also tries to acquire an index on a column defined in some other table that is no way related to the UPDATE statement... And the SELECT statement that won the deadlock situation had nothing to do with the table or index in the update statement but tried to acquire an index on the table in UPDATE statement. eventually causing the DEADLOCK.

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  • Database - Designing an "Events" Table

    - by Alix Axel
    After reading the tips from this great Nettuts+ article I've come up with a table schema that would separate highly volatile data from other tables subjected to heavy reads and at the same time lower the number of tables needed in the whole database schema, however I'm not sure if this is a good idea since it doesn't follow the rules of normalization and I would like to hear your advice, here is the general idea: I've four types of users modeled in a Class Table Inheritance structure, in the main "user" table I store data common to all the users (id, username, password, several flags, ...) along with some TIMESTAMP fields (date_created, date_updated, date_activated, date_lastLogin, ...). To quote the tip #16 from the Nettuts+ article mentioned above: Example 2: You have a “last_login” field in your table. It updates every time a user logs in to the website. But every update on a table causes the query cache for that table to be flushed. You can put that field into another table to keep updates to your users table to a minimum. Now it gets even trickier, I need to keep track of some user statistics like how many unique times a user profile was seen how many unique times a ad from a specific type of user was clicked how many unique times a post from a specific type of user was seen and so on... In my fully normalized database this adds up to about 8 to 10 additional tables, it's not a lot but I would like to keep things simple if I could, so I've come up with the following "events" table: |------|----------------|----------------|--------------|-----------| | ID | TABLE | EVENT | DATE | IP | |------|----------------|----------------|--------------|-----------| | 1 | user | login | 201004190030 | 127.0.0.1 | |------|----------------|----------------|--------------|-----------| | 1 | user | login | 201004190230 | 127.0.0.1 | |------|----------------|----------------|--------------|-----------| | 2 | user | created | 201004190031 | 127.0.0.2 | |------|----------------|----------------|--------------|-----------| | 2 | user | activated | 201004190234 | 127.0.0.2 | |------|----------------|----------------|--------------|-----------| | 2 | user | approved | 201004190930 | 217.0.0.1 | |------|----------------|----------------|--------------|-----------| | 2 | user | login | 201004191200 | 127.0.0.2 | |------|----------------|----------------|--------------|-----------| | 15 | user_ads | created | 201004191230 | 127.0.0.1 | |------|----------------|----------------|--------------|-----------| | 15 | user_ads | impressed | 201004191231 | 127.0.0.2 | |------|----------------|----------------|--------------|-----------| | 15 | user_ads | clicked | 201004191231 | 127.0.0.2 | |------|----------------|----------------|--------------|-----------| | 15 | user_ads | clicked | 201004191231 | 127.0.0.2 | |------|----------------|----------------|--------------|-----------| | 15 | user_ads | clicked | 201004191231 | 127.0.0.2 | |------|----------------|----------------|--------------|-----------| | 15 | user_ads | clicked | 201004191231 | 127.0.0.2 | |------|----------------|----------------|--------------|-----------| | 15 | user_ads | clicked | 201004191231 | 127.0.0.2 | |------|----------------|----------------|--------------|-----------| | 2 | user | blocked | 201004200319 | 217.0.0.1 | |------|----------------|----------------|--------------|-----------| | 2 | user | deleted | 201004200320 | 217.0.0.1 | |------|----------------|----------------|--------------|-----------| Basically the ID refers to the primary key (id) field in the TABLE table, I believe the rest should be pretty straightforward. One thing that I've come to like in this design is that I can keep track of all the user logins instead of just the last one, and thus generate some interesting metrics with that data. Due to the nature of the events table I also thought of making some optimizations, such as: #9: Since there is only a finite number of tables and a finite (and predetermined) number of events, the TABLE and EVENTS columns could be setup as ENUMs instead of VARCHARs to save some space. #14: Store IPs as UNSIGNED INT with INET_ATON() instead of VARCHARs. Store DATEs as TIMESTAMPs instead of DATETIMEs. Use the ARCHIVE (or the CSV?) engine instead of InnoDB / MyISAM. Overall, each event would only consume 14 bytes which is okay for my traffic I guess. Pros: Ability to store more detailed data (such as logins). No need to design (and code for) almost a dozen additional tables (dates and statistics). Reduces a few columns per table and keeps volatile data separated. Cons: Non-relational (still not as bad as EAV): SELECT * FROM events WHERE id = 2 AND table = 'user' ORDER BY date DESC(); 6 bytes overhead per event (ID, TABLE and EVENT). I'm more inclined to go with this approach since the pros seem to far outweigh the cons, but I'm still a little bit reluctant.. Am I missing something? What are your thoughts on this? Thanks!

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  • Normalizing a table

    - by Alex
    I have a legacy table, which I can't change. The values in it can be modified from legacy application (application also can't be changed). Due to a lot of access to the table from new application (new requirement), I'd like to create a temporary table, which would hopefully speed up the queries. The actual requirement, is to calculate number of business days from X to Y. For example, give me all business days from Jan 1'st 2001 until Dec 24'th 2004. The table is used to mark which days are off, as different companies may have different days off - it isn't just Saturday + Sunday) The temporary table would be created from a .NET program, each time user enters the screen for this query (user may run query multiple times, with different values, table is created once), so I'd like it to be as fast as possible. Approach below runs in under a second, but I only tested it with a small dataset, and still it takes probably close to half a second, which isn't great for UI - even though it's just the overhead for first query. The legacy table looks like this: CREATE TABLE [business_days]( [country_code] [char](3) , [state_code] [varchar](4) , [calendar_year] [int] , [calendar_month] [varchar](31) , [calendar_month2] [varchar](31) , [calendar_month3] [varchar](31) , [calendar_month4] [varchar](31) , [calendar_month5] [varchar](31) , [calendar_month6] [varchar](31) , [calendar_month7] [varchar](31) , [calendar_month8] [varchar](31) , [calendar_month9] [varchar](31) , [calendar_month10] [varchar](31) , [calendar_month11] [varchar](31) , [calendar_month12] [varchar](31) , misc. ) Each month has 31 characters, and any day off (Saturday + Sunday + holiday) is marked with X. Each half day is marked with an 'H'. For example, if a month starts on a Thursday, than it will look like (Thursday+Friday workdays, Saturday+Sunday marked with X): ' XX XX ..' I'd like the new table to look like so: create table #Temp (country varchar(3), state varchar(4), date datetime, hours int) And I'd like to only have rows for days which are off (marked with X or H from previous query) What I ended up doing, so far is this: Create a temporary-intermediate table, that looks like this: create table #Temp_2 (country_code varchar(3), state_code varchar(4), calendar_year int, calendar_month varchar(31), month_code int) To populate it, I have a union which basically unions calendar_month, calendar_month2, calendar_month3, etc. Than I have a loop which loops through all the rows in #Temp_2, after each row is processed, it is removed from #Temp_2. To process the row there is a loop from 1 to 31, and substring(calendar_month, counter, 1) is checked for either X or H, in which case there is an insert into #Temp table. [edit added code] Declare @country_code char(3) Declare @state_code varchar(4) Declare @calendar_year int Declare @calendar_month varchar(31) Declare @month_code int Declare @calendar_date datetime Declare @day_code int WHILE EXISTS(SELECT * From #Temp_2) -- where processed = 0) BEGIN Select Top 1 @country_code = t2.country_code, @state_code = t2.state_code, @calendar_year = t2.calendar_year, @calendar_month = t2.calendar_month, @month_code = t2.month_code From #Temp_2 t2 -- where processed = 0 set @day_code = 1 while @day_code <= 31 begin if substring(@calendar_month, @day_code, 1) = 'X' begin set @calendar_date = convert(datetime, (cast(@month_code as varchar) + '/' + cast(@day_code as varchar) + '/' + cast(@calendar_year as varchar))) insert into #Temp (country, state, date, hours) values (@country_code, @state_code, @calendar_date, 8) end if substring(@calendar_month, @day_code, 1) = 'H' begin set @calendar_date = convert(datetime, (cast(@month_code as varchar) + '/' + cast(@day_code as varchar) + '/' + cast(@calendar_year as varchar))) insert into #Temp (country, state, date, hours) values (@country_code, @state_code, @calendar_date, 4) end set @day_code = @day_code + 1 end delete from #Temp_2 where @country_code = country_code AND @state_code = state_code AND @calendar_year = calendar_year AND @calendar_month = calendar_month AND @month_code = month_code --update #Temp_2 set processed = 1 where @country_code = country_code AND @state_code = state_code AND @calendar_year = calendar_year AND @calendar_month = calendar_month AND @month_code = month_code END I am not an expert in SQL, so I'd like to get some input on my approach, and maybe even a much better approach suggestion. After having the temp table, I'm planning to do (dates would be coming from a table): select cast(convert(datetime, ('01/31/2012'), 101) -convert(datetime, ('01/17/2012'), 101) as int) - ((select sum(hours) from #Temp where date between convert(datetime, ('01/17/2012'), 101) and convert(datetime, ('01/31/2012'), 101)) / 8) Besides the solution of normalizing the table, the other solution I implemented for now, is a function which does all this logic of getting the business days by scanning the current table. It runs pretty fast, but I'm hesitant to call a function, if I can instead add a simpler query to get result. (I'm currently trying this on MSSQL, but I would need to do same for Sybase ASE and Oracle)

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  • On asp:Table Control how do we create a thead ?

    - by balexandre
    from MSDN article on the subject we can see that we create a TableHeaderRowthat conatins TableHeaderCells. but they add the table header like this: myTable.Row.AddAt(0, headerRow); witch outputs the HTML: <table id="Table1" ... > <tr> <th scope="column" abbr="Col 1 Head">Column 1 Header</th> <th scope="column" abbr="Col 2 Head">Column 2 Header</th> <th scope="column" abbr="Col 3 Head">Column 3 Header</th> </tr> <tr> <td>(0,0)</td> <td>(0,1)</td> <td>(0,2)</td> </tr> ... and it should have <thead> and <tbody> (so it works seamless with tablesorter) :) <table id="Table1" ... > <thead> <tr> <th scope="column" abbr="Col 1 Head">Column 1 Header</th> <th scope="column" abbr="Col 2 Head">Column 2 Header</th> <th scope="column" abbr="Col 3 Head">Column 3 Header</th> </tr> </thead> <tbody> <tr> <td>(0,0)</td> <td>(0,1)</td> <td>(0,2)</td> </tr> ... </tbody> the HTML aspx code is <asp:Table ID="Table1" runat="server" /> How can I output the correct syntax? Just as information, the GridViewcontrol has this builed in as we just need to set teh Accesbility and use the HeaderRow gv.UseAccessibleHeader = true; gv.HeaderRow.TableSection = TableRowSection.TableHeader; gv.HeaderRow.CssClass = "myclass"; but the question is for the Table control.

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  • css display:table first column too wide

    - by Mestore
    I have a css table setup like this: <div class='table'> <div> <span>name</span> <span>details</span> </div> </div> The css for the table is: .table{ display:table; width:100%; } .table div{ text-align:right; display:table-row; border-collapse: separate; border-spacing: 0px; } .table div span:first-child { text-align:right; } .table div span { vertical-align:top; text-align:left; display:table-cell; padding:2px 10px; } As it stands the two columns are split evenly between the space occupied by the width of the table. I'm trying to get the first column only to be as wide as is needed by the text occupying it's cells The table is an unknown width, as are the columns/cells.

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  • Lock statement vs Monitor.Enter method.

    - by Vokinneberg
    I suppose it is an interesting code example. We have a class, let's call it Test with Finalize method. In Main method here is two code blocks where i am using lock statement and Monitor.Enter call. Also i have two instances of class Test here. The experiment is pretty simple - nulling Test variable within locking block and try to collect it manually with GC.Collect method call. So, to see the Finilaze call i am calling GC.WaitForPendingFinalizers method. Everything is very simple as you can see. By defenition of lock statement it's opens by compiler to try{...}finally{..} block with Minitor.Enter call inside of try block and Monitor.Exit in finally block. I've tryed to implement try-finally block manually. I've expected the same behaviour in both cases. in case of using lock and in case of unsing Monitor.Enter. But, surprize, surprize - it is different as you can see below. public class Test : IDisposable { private string name; public Test(string name) { this.name = name; } ~Test() { Console.WriteLine(string.Format("Finalizing class name {0}.", name)); } } class Program { static void Main(string[] args) { var test1 = new Test("Test1"); var test2 = new Test("Tesst2"); lock (test1) { test1 = null; Console.WriteLine("Manual collect 1."); GC.Collect(); GC.WaitForPendingFinalizers(); Console.WriteLine("Manual collect 2."); GC.Collect(); } var lockTaken = false; System.Threading.Monitor.Enter(test2, ref lockTaken); try { test2 = null; Console.WriteLine("Manual collect 3."); GC.Collect(); GC.WaitForPendingFinalizers(); Console.WriteLine("Manual collect 4."); GC.Collect(); } finally { System.Threading.Monitor.Exit(test2); } Console.ReadLine(); } } Output of this example is Manual collect 1. Manual collect 2. Manual collect 3. Finalizing class name Test2. Manual collect 4. And null reference exception in last finally block because test2 is null reference. I've was surprised and disasembly my code into IL. So, here is IL dump of Main method. .entrypoint .maxstack 2 .locals init ( [0] class ConsoleApplication2.Test test1, [1] class ConsoleApplication2.Test test2, [2] bool lockTaken, [3] bool <>s__LockTaken0, [4] class ConsoleApplication2.Test CS$2$0000, [5] bool CS$4$0001) L_0000: nop L_0001: ldstr "Test1" L_0006: newobj instance void ConsoleApplication2.Test::.ctor(string) L_000b: stloc.0 L_000c: ldstr "Tesst2" L_0011: newobj instance void ConsoleApplication2.Test::.ctor(string) L_0016: stloc.1 L_0017: ldc.i4.0 L_0018: stloc.3 L_0019: ldloc.0 L_001a: dup L_001b: stloc.s CS$2$0000 L_001d: ldloca.s <>s__LockTaken0 L_001f: call void [mscorlib]System.Threading.Monitor::Enter(object, bool&) L_0024: nop L_0025: nop L_0026: ldnull L_0027: stloc.0 L_0028: ldstr "Manual collect." L_002d: call void [mscorlib]System.Console::WriteLine(string) L_0032: nop L_0033: call void [mscorlib]System.GC::Collect() L_0038: nop L_0039: call void [mscorlib]System.GC::WaitForPendingFinalizers() L_003e: nop L_003f: ldstr "Manual collect." L_0044: call void [mscorlib]System.Console::WriteLine(string) L_0049: nop L_004a: call void [mscorlib]System.GC::Collect() L_004f: nop L_0050: nop L_0051: leave.s L_0066 L_0053: ldloc.3 L_0054: ldc.i4.0 L_0055: ceq L_0057: stloc.s CS$4$0001 L_0059: ldloc.s CS$4$0001 L_005b: brtrue.s L_0065 L_005d: ldloc.s CS$2$0000 L_005f: call void [mscorlib]System.Threading.Monitor::Exit(object) L_0064: nop L_0065: endfinally L_0066: nop L_0067: ldc.i4.0 L_0068: stloc.2 L_0069: ldloc.1 L_006a: ldloca.s lockTaken L_006c: call void [mscorlib]System.Threading.Monitor::Enter(object, bool&) L_0071: nop L_0072: nop L_0073: ldnull L_0074: stloc.1 L_0075: ldstr "Manual collect." L_007a: call void [mscorlib]System.Console::WriteLine(string) L_007f: nop L_0080: call void [mscorlib]System.GC::Collect() L_0085: nop L_0086: call void [mscorlib]System.GC::WaitForPendingFinalizers() L_008b: nop L_008c: ldstr "Manual collect." L_0091: call void [mscorlib]System.Console::WriteLine(string) L_0096: nop L_0097: call void [mscorlib]System.GC::Collect() L_009c: nop L_009d: nop L_009e: leave.s L_00aa L_00a0: nop L_00a1: ldloc.1 L_00a2: call void [mscorlib]System.Threading.Monitor::Exit(object) L_00a7: nop L_00a8: nop L_00a9: endfinally L_00aa: nop L_00ab: call string [mscorlib]System.Console::ReadLine() L_00b0: pop L_00b1: ret .try L_0019 to L_0053 finally handler L_0053 to L_0066 .try L_0072 to L_00a0 finally handler L_00a0 to L_00aa I does not see any difference between lock statement and Monitor.Enter call. So, why i steel have a reference to the instance of test1 in case of lock, and object is not collected by GC, but in case of using Monitor.Enter it is collected and finilized?

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  • Entire Table is pushed to the next page when rendering a SSRS 2005 Report (as .pdf) in SSRS 2008

    - by Pwninstein
    I have a SSRS 2005 report that I'm rendering in SSRS 2008 as a .pdf. The report contains (among other things) a table that's very simple: header row, details, no footer, no aggregation, no grouping, keep together = false, pageBreakAtStart = false, pageBreakAtEnd = false, repeatHeaderOnNewPage = true. I resized the table to be much narrower than the body of the report just to be sure it wasn't extending beyond the bounds of the report, pushing everything down. But, no matter what I try, if some of the detail rows in that table would need to be pushed to the next page, then the ENTIRE TABLE is pushed to the next page, not just the extra rows. So my question is: Is there a workaround for this problem, is this a known issue, or is it even possible to get this 2005 report to render properly in 2008? NOTE: this is related to a question that I previously asked here, and is based on this MSDN forum post started by a coworker. This question is not the same as my previous question, as I'd like to see things work properly in with a 2005 report. If it's not possible, that would be good to know, as it would indicate that we need to upgrade one of our servers to SQL 2008. Thanks!

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  • Way to turn on keyboard's caps-lock light without actually turning on caps-lock?

    - by cksubs
    I'm writing a program that uses caps-lock as a toggle switch. It would be nice to set the LED of the key to show that my program is on or off, like the capslock key does naturally. I know that I could just SendInput('Capslock'); or whatever to actually turn caps-lock on and off. But my app is a typing program, and I don't want to have to deal with translating the all-caps keys that turning it on would give me into their lower/upper cases. I might go that route eventually, but not for this version. I would however be interested in just turning on the LED light WITHOUT actually turning on caps-lock. Is there any way to do that? Thank you.

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  • Acquiring Table Lock in Database - Interview Question

    - by harigm
    One of my interview Questions, if multiple users across the world are accessing the application, in which it uses a Table which has a Primary Key as Auto Increment Field. The Question how can you prevent the other user getting the Same Primary key when the other user is executing? My answer was I will obtain the Lock on the table and I will make the user to wait Until that user is released with the Primary key. But the Question How do you acquire the Table lock programmatically and implement this? If there are 1000 users coming every minute to the application, if you explicity hold the lock on the table, then the application will become slower? How do you manage this? Please suggest the possible answers for the above question

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  • Implementing a Mutex Lock in C

    - by Adam
    I'm trying to make a really mutex in C and for some reason I'm getting cases where two threads are getting the lock at the same time, which shouldn't be possible. Any ideas why it's not working? void mutexLock(mutex_t *mutexlock, pid_t owner) { int failure; while(mutexlock->mx_state == 0 || failure || mutexlock->mx_owner != owner) { failure = 1; if (mutexlock->mx_state == 0) { asm( "test:" "movl $0x01,%%eax\n\t" // move 1 to eax "xchg %%eax,%0\n\t" // try to set the lock bit "mov %%eax,%1\n\t" // export our result to a test var "test %%eax,%%eax\n\t" "jnz test\n\t" :"=r"(mutexlock->mx_state),"=r"(failure) :"r"(mutexlock->mx_state) :"%eax" ); } if (failure == 0) { mutexlock->mx_owner = owner; //test to see if we got the lock bit } } }

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  • How to show that the double-checked-lock pattern with Dictionary's TryGetValue is not threadsafe in

    - by Amir
    Recently I've seen some C# projects that use a double-checked-lock pattern on a Dictionary. Something like this: private static readonly object _lock = new object(); private static volatile IDictionary<string, object> _cache = new Dictionary<string, object>(); public static object Create(string key) { object val; if (!_cache.TryGetValue(key, out val)) { lock (_lock) { if (!_cache.TryGetValue(key, out val)) { val = new object(); // factory construction based on key here. _cache.Add(key, val); } } } return val; } This code is incorrect, since the Dictionary can be "growing" the collection in _cache.Add() while _cache.TryGetValue (outside the lock) is iterating over the collection. It might be extremely unlikely in many situations, but is still wrong. Is there a simple program to demonstrate that this code fails? Does it make sense to incorporate this into a unit test? And if so, how?

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  • Using accelerometer to detect iPad lock switch trigger?

    - by DevDevDev
    So for complicated reasons I am managing view rotations myself, and am only implementing UIDeviceOrientationPortrait as the autorotating orientation. Anyway, when one clicks the screen lock on the iPad, the device will rotate to UIDeviceOrientationPortrait, which will cause my code to rotate, which I do not want to happen. For instance of the user is holding the device in "landscape mode", i.e. I have already manually rotated the UI to landscape mode, and he/she clicks the screen lock, it will rotate the UI to portrait mode, even though the user did not move the device at all. So somehow I need a way to differentiate between rotations to portrait mode occuring from the screen lock, and those occuring from device rotation. As such, I would like somehow to use the accelerometer to detect whether or not the device was actually 'rotated' or whether the button was clicked. Thanks!

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  • Jquery add table row after the row which calling the jquery.

    - by marharépa
    Hello! I've got a table. <table id="servers" ...> ... {section name=i loop=$ownsites} <tr id="site_id_{$ownsites[i].id}"> ... <td>{$ownsites[i].phone}</td> <td class="icon"><a id="{$ownsites[i].id}" onClick="return makedeleterow(this.getAttribute('id'));" ...></a></td> </tr> {/section} <tbody> </table> And this java script. <script type="text/javascript"> function makedeleterow(id) { $('#delete').remove(); $('#servers').append($(document.createElement("tr")).attr({id: "delete"})); $('#delete').append($(document.createElement("td")).attr({colspan: "9", id: "deleter"})); $('#deleter').text('Biztosan törölni szeretnéd ezt a weblapod?'); $('#deleter').append($(document.createElement("input")).attr({type: "submit", id: id, onClick: "return truedeleterow(this.getAttribute('id'))"})); $('#deleter').append($(document.createElement("input")).attr({type: "hidden", name: "website_del", value: id})); } </script> It's workin fine, it makes a tr after the table's last tr and put the info to it, and the delete function also works fine. But i'd like to make this append AFTER the tr (with td class="icon") which calling the script. How can i do this?

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  • Oracle global lock across process

    - by Jimm
    I would like to synchronize access to a particular insert. Hence, if multiple applications execute this "one" insert, the inserts should happen one at a time. The reason behind synchronization is that there should only be ONE instance of this entity. If multiple applications try to insert the same entity,only one should succeed and others should fail. One option considered was to create a composite unique key, that would uniquely identify the entity and rely on unique constraint. For some reasons, the dba department rejected this idea. Other option that came to my mind was to create a stored proc for the insert and if the stored proc can obtain a global lock, then multiple applications invoking the same stored proc, though in their seperate database sessions, it is expected that the stored proc can obtain a global lock and hence serialize the inserts. My question is it possible to for a stored proc in oracle version 10/11, to obtain such a lock and any pointers to documentation would be helpful.

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  • is it possible to lock oracle 10g database table with C#/(ADO?).NET 2.0

    - by matti
    I have a table that contains a maximum value that needs to be get and set by multiple programs. How can I lock the table for a while when old value is got and new is updated in C#? In other words: string sql = "lock table MaxValueTable in exclusive mode"; using (DbCommand cmd = cnctn.CreateCommand()) { cmd.CommandText = sql; // execute command somehow!! } maxValue = GetMaxValue(); SetMaxValue(maxValue + X); sql = "lock table MaxValueTable in share mode"; using (DbCommand cmd = cnctn.CreateCommand()) { cmd.CommandText = sql; // execute command somehow!! } -BR: Matti

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  • net c# lock statement in data access layer

    - by Pedro Rivera
    I saw a code where they have the data access layer like this: public class CustomerDA{ private static readonly object _sync = new object(); private static readonly CustomerDA _mutex = new CustomerDA(); private CustomerDA(){ } public CustomerDA GetInstance(){ lock(_sync){ return _mutex; } } public DataSet GetCustomers(){ //database SELECT //return a DataSet } public int UpdateCustomer(some parameters){ //update some user } } public class CustomerBO{ public DataSet GetCustomers(){ //some bussiness logic return CustomerDA.GetInstance().GetCustomers(); } } I was using it, but start thinking... "and what if had to build a facebook like application where there are hundreds of thousands of concurrent users? would I be blocking each user from doing his things until the previous user ends his database stuff? and for the Update method, is it useful to LOCK THREADS in the app when database engines already manage concurrency at database server level?" Then I started to think about moving the lock to the GetCustomers and UpdateCustomer methods, but think again: "is it useful at all?"

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  • one table is shared between several websites

    - by sami
    I have a static table that's shared by several websites. By static, I mean that the data is read but never updated by the websites. Currently, all websites are served from the same server but that may change. I want to minimize the need for creating/maintaining this table for each of the websites, so I thought about turning it to an xml file that's stored in a shared library that all websites have access to. The problem is I use an ORM and use forign key constraints to ensure integrity of the ids used from that table, so by removing that table out of the MySQL database into an XML file, will this affect the integrity of the ids coming from that table? My table looks like this <table name="entry"> <column name="id" type="INTEGER" primaryKey="true" autoIncrement="true" /> <column name="title" type="VARCHAR" size="500" required="true" /> </table> and I use it as a foreign key in other tables <table name="refer"> <column name="id" type="INTEGER" primaryKey="true" autoIncrement="true" /> <column name="linkto" type="INTEGER"/> <foreign-key foreignTable="entry"> <reference local="linkto" foreign="id" /> </foreign-key> </table> So I'm wondering if I remove that table out of the database, is there a way to retain that referential integrity? And of course are these any other efficient ways to do the same thing? I just don't want to have to repeat that table for several websites.

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  • How do I use price data in one table for a calculation that is stored in another table?

    - by shane
    I'm still leanring PHP/MySQL but have learned quite a bit thanks to codies on StackOverflow. I'm trying to setup a sort of room reservations system using two tables: SETUP: Room price table: Has, prices for a type room a client may want to rent as well as the dates (day of week) they wish to use it. Pricing varies based on day of the week and per room. I've setup a different table for each room type as each room type carries different pricing for each day of the week. So, There is an Alpha room table, Bravo room, etc. Within Alpha table are headers for the days of the week with pricing pre-entered into the rows. Client info table: Has the name, address, date of room use, etc data for the specific client. EXAMPLE: Alpha-room price table: Sun = $100; Mon = $200; Tue=$300 and so on. Bravo-room price table: Sun = $100; Mon = $200; Tue=$300 and so on. Client data table: ClientName; date-of-room-use; address; day_subtotal; grand_total. QUESTION: I'm trying to find PHP code that will: look at the date of room use in the client data table, look up the associated cost for that date in the specific room pricing table, record that unit cost in the day subtotal of the client data table and sum a grand total in the grand total row of the client data table (assuming the room may be used more than one day by the customer). I know there's something to do with join but I'm finding it difficult to grasp the concept and, if someone can demonstrate using this example, I think I will have a better understanding of how to work this sort of transaction. Thank you ALL in advance for your suggestions or alternatvie approaches.

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  • innodb lock wait timeout

    - by shantanuo
    As per the documentation link given below: When a lock wait timeout occurs, the current statement is not executed. The current transaction is not rolled back. (Until MySQL 5.0.13 InnoDB rolled back the entire transaction if a lock wait timeout happened. You can restore this behavior by starting the server with the --innodb_rollback_on_timeout option, available as of MySQL 5.0.32. http://dev.mysql.com/doc/refman/5.0/en/innodb-parameters.html#sysvar_innodb_lock_wait_timeout Does it mean that when a lock wait timeout occurs, it compromises the transactional integrity? "roollback on timeout" was the default behaviour till 5.0.13 and I guess that was the correct way to handle such situations. Does anyone think that this should be the default behaviour and the user should not be asked to add a parameter for a functionality that is taken for granted?

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  • Which text margin does SWT Table use when drawing text?

    - by Zordid
    I got a relatively easy question - but I cannot find anything anywhere to answer it. I use a simple SWT table widget in my application that displays only text in the cells. I got an incremental search feature and want to highlight text snippets in all cells if they match. So when typing "a", all "a"s should be highlighted. To get this, I add an SWT.EraseItem listener to interfere with the background drawing. If the current cell's text contains the search string, I find the positions and calculate relative x-coordinates within the text using event.gc.stringExtent - easy. With that I just draw rectangles "behind" the occurrences. Now, there's a flaw in this. The table does not draw the text without a margin, so my x coordinate does not really match - it is slightly off by a few pixels! But how many?? Where do I retrieve the cell's text margins that table's own drawing will use? No clue. Cannot find anything. :-( Bonus question: the table's draw method also shortens text and adds "..." if it does not fit into the cell. Hmm. My occurrence finder takes the TableItem's text and thus also tries to mark occurrences that are actually not visible because they are consumed by the "...". How do I get the shortened text and not the "real" text within the EraseItem draw handler? Thanks!

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  • Building static (but complicated) lookup table using templates.

    - by MarkD
    I am currently in the process of optimizing a numerical analysis code. Within the code, there is a 200x150 element lookup table (currently a static std::vector < std::vector < double ) that is constructed at the beginning of every run. The construction of the lookup table is actually quite complex- the values in the lookup table are constructed using an iterative secant method on a complicated set of equations. Currently, for a simulation, the construction of the lookup table is 20% of the run time (run times are on the order of 25 second, lookup table construction takes 5 seconds). While 5-seconds might not seem to be a lot, when running our MC simulations, where we are running 50k+ simulations, it suddenly becomes a big chunk of time. Along with some other ideas, one thing that has been floated- can we construct this lookup table using templates at compile time? The table itself never changes. Hard-coding a large array isn't a maintainable solution (the equations that go into generating the table are constantly being tweaked), but it seems that if the table can be generated at compile time, it would give us the best of both worlds (easily maintainable, no overhead during runtime). So, I propose the following (much simplified) scenario. Lets say you wanted to generate a static array (use whatever container suits you best- 2D c array, vector of vectors, etc..) at compile time. You have a function defined- double f(int row, int col); where the return value is the entry in the table, row is the lookup table row, and col is the lookup table column. Is it possible to generate this static array at compile time using templates, and how?

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