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[Maria-developers] Review request[major 5.3/5.5 bug]: MDEV-4511 Assertion `scale <= precision' fails on GROUP BY TIMEDIFF with incorrect types, , Agile Board, , Export
by Alexander Barkov 03 Jun '14

03 Jun '14

Hello Sergei, A few weeks ago we fixed this bug for 10.0 by changing temporal items not to have decimals=NOT_FIXED_DEC (more MySQL-5.6 compatibility), and agreed to have a separate patch for the pre-10.0 branches. This patch is for 5.3 and 5.5 only. It back-ports the mdev-4511 tests from 10.0 as is. But it does not touch the NOT_FIXED_DEC behavior of the temporal items and fixes the problem in a different way. Greetings.

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[Maria-developers] POWER interest
by Colin Charles 03 Jun '14

03 Jun '14

Hi, It seems we have a POWER8 box and soon will start doing builds on this platform Stewart Smith (currently at IBM) seems to be doing some work on MySQL 5.6 and MySQL 5.7 for POWER8 systems - there doesn't seem to be much attention being paid to MariaDB 10. Ideally, our fixes that are being picked up from Stewart or focused on POWER should be targeted at 10.1 I'm thinking (unless there's customer interest for the 10.0 series -- which may very likely be the case) So far, I've noted GIS precise has an open failure, and maybe its a great idea for Holyfoot to use the POWER8 system to start fixing it: https://mariadb.atlassian.net/browse/MDEV-4153 From MySQL bugs system we see multiple examples from Stewart's blog posts - some are InnoDB specific so we will inherit them during a merge - some aren't like mysql#72715 (character set code endianness dependent on CPU type rather than endianness of CP) https://www.flamingspork.com/blog/2014/06/03/1-million-sql-queries-per-seco… https://www.flamingspork.com/blog/2014/06/03/mysql-5-7-on-power/ Relevant stuff that we may want to look at: http://bugs.mysql.com/search.php?cmd=display&status=Active&tags=PowerPC cheers, -colin -- Colin Charles, Chief Evangelist, SkySQL - The MariaDB Company blog: http://bytebot.net/blog/| t: +6-012-204-3201 | Skype: colincharles

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[Maria-developers] [GSoC] First two weeks into coding!
by sriram patil 03 Jun '14

03 Jun '14

Hi all, I have created a blog to write the details of the work that I do as part of GSoC'14. Following is the link to my first blog post explaining the details of the work that I have done during the last two weeks. http://goo.gl/PYoVZb I will be writing these blog posts every weekend from now on and will share it on the developer mailing list every Monday. Suggestions/reviews are welcome. Thanks, Sriram

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[Maria-developers] Possible race condition or NULL pointer triggered by OQGraph
by Andrew McDonnell 02 Jun '14

02 Jun '14

Hi all (Cross-posted to oqgraph-developers, maria-developers) I am trying to track down a segfault apparently triggered by concurrent execution of queries through OQGraph - for context, see: https://mariadb.atlassian.net/browse/MDEV-6282 I am however a bit confused as to what is going on, because at least some of the information leads me to suspect that there could be more going on here than just a simple race condition. --Immediate Cause-- On the surface, a segfault appears to be caused in a method in sql_class.h, Statement::check_limit_rows_examined() dereferencing a NULL pointer, `lex`. The method check_limit_rows_examined() was called from sql_class.h method handler::increment_statistics() . --Analysis-- A quick inspection reveals that a NULL value for `lex` is actually perfectly valid some of the time, although I am nowhere near familiar enough with the code to really understand when or why. Specifically, `lex` is a member of the base class Statement, which is initialised to either point to THD::main_lex via a constructor , or intentionally to NULL from construction of an object Prepared_statement() (sql_prepare.cc) To my mind, if there is going to be a possibility of a pointer being NULL, then all uses of that pointer should be checking for that. I am hoping that the bug reporter can prove or otherwise my hypothesis with his particular scenario, although I am suspicious that there may be additional issues to be dealt with; it is quite possible that lex being NULL is a red herring, being caused by a race condition memory overrun elsewhere. However, I think it is still a good idea to NULL check pointers that could be set to NULL intentionally. I can submit a pull request if the following patch is agreeable: diff --git a/sql/sql_class.h b/sql/sql_class.h index 5898d9e..957acf3 100644 --- a/sql/sql_class.h +++ b/sql/sql_class.h @@ -2475,8 +2475,10 @@ public: */ void check_limit_rows_examined() { - if (++accessed_rows_and_keys > lex->limit_rows_examined_cnt) + ++accessed_rows_and_keys; + if (lex && accessed_rows_and_keys > lex->limit_rows_examined_cnt) { killed= ABORT_QUERY; + } } --Aside-- Immediately prior to the check_limit_rows_examined() call is a call to macro status_var_increment(). Comments around the macro indicate it is often likely to be called in a mutli-threaded context, but the data is such that it is possible to disable protection with the only side effect being an occasionally 'inaccurate' result. Is it possible however, that check_limit_rows_examined() is not thread-safe and should have some protection? cheers, Andrew --A

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[Maria-developers] MDEV-4051 INET6_ATON() and INET6_NTOA()
by Alexander Barkov 02 Jun '14

02 Jun '14

Hello Ian, I have merged these functions from MySQL-5.6 into 10.0: INET6_ATON() INET6_NTOA() IS_IPV4() IS_IPV4_COMPAT() IS_IPV4_MAPPED() IS_IPV6() Can you please document them? The corresponding article in the MySQL manual is here: http://dev.mysql.com/doc/refman/5.6/en/miscellaneous-functions.html Thanks.

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[Maria-developers] KB page on switching from bazaar to git.
by Sergey Petrunia 27 May '14

27 May '14

Hi, I was doing some stuff in git already, and so I have created a git cheatsheet with equivalents of bzr commands that were useful in MariaDB development: https://mariadb.com/kb/en/using-git/ It is not finished, any additions are welcome. Elena has agreed to look at creating a commit trigger that sends commit emails (currently, github sends emails on push (not commit), and these do not include diffs) BR Sergei -- Sergei Petrunia, Software Developer MariaDB | Skype: sergefp | Blog: http://s.petrunia.net/blog

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[Maria-developers] CREATE OR REPLACE DATABASE algorithm
by sriram patil 27 May '14

27 May '14

Hi Alexander and all, Following are the steps that I am following for implementing "CREATE OR REPLACE" for DATABASE "..." signifies, there exists one or more lines of code in that block of the function. mysql_create_db(...) ... ... if(db exists) { if(create_or_replace) { if(DROP_ACL access not granted) { // Error 1 DBUG_RETURN(-1) } if(mysql_rm_db(...) unsuccessful) { // Error 2 DBUG_RETURN(-1) } Reset m_status from diagnostics cause it is changed by mysql_rm_db. Proceed with normal create db. } else if(if not exists) { ... } else ... } ... ... } Is the above algorithm correct? Also, I am not yet sure which errors should be displayed at both the places "Error 1" and "Error 2". I have written and tested the above code. It is working fine. Testing involves running all the existing test cases and executing "CREATE OR REPLACE DATABASE" command on the console manually. "IF NOT EXISTS" gives error if used with "CREATE OR REPLACE". Any other test cases I need to consider? Thanks, Sriram

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[Maria-developers] FOR JSON
by Alexander Barkov 26 May '14

26 May '14

Hello Monty, We discussed extracting data in JSON format today, to make it possible to return data as a single JSON value (as a result set consisting of a single row and a single column): SELECT id,name,address FROM users FOR JSON; Note, in some cases the result of a such query can obviously be very huge. So it would be nice to be able to use "FOR JSON" in subselects, like this: SELECT id, (SELECT name,address FROM users AS b WHERE a.id= b.id FOR JSON) AS RowJSON FROM users AS a; This query will return a result set with multiple rows (one row per one record) and with two columns: - the ID, as a regular number - the JSON value with "name" and "address" embedded into it. Or, another example, if one does not need "id" as a separate column: SELECT (SELECT id,name,address FROM users AS b WHERE a.id= b.id FOR JSON) AS RowJSON FROM users AS a; This query will return a result set with multiple rows (one row per one record) with a single JSON value embedding all three columns: "id", "name" and "address".

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[Maria-developers] MariaDB 10.1 is now on github!
by Sergei Golubchik 26 May '14

26 May '14

Hi! I'm happy to announce that MariaDB-10.1 tree has been completely migrated to github. Since now on we'll use github for the new development in MariaDB. It's https://github.com/MariaDB/server, go on, fork it, hack around, submit pull requests. Have fun! Older trees (10.0, 5.5, 5.3, 5.2, 5.1) are not on github - we do hope to migrate them too eventually, but at the moment they are still on launchpad. If you're a maria-captain on launchpad - for you to get write access to the mariadb repository on github you need to tell me your github account name. Regards, Sergei P.S.: Don't forget that 10.1 is still *pre-alpha*. You've been warned.

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Re: [Maria-developers] MariaDB 10.1 is now on github!
by Sergei Golubchik 26 May '14

26 May '14

Hi, Binod! First: please send questions like this to maria-developers(a)lists.launchpad.net it's a public mailing list dedicated to MySQL and MariaDB internals, source code, and related things. I am subscribed, so I'll see you mail there, and you may be sure I will, because it won't be accidentally catched by my spam filter, or sorted out in some obscure folder. Furthermore other subscribers will see your question and could reply if I will be not available (e.g. I could be travelling). Thank you. On May 26, Binod Bista wrote: > Hi Sergei, > > Thanks for the info. Just to interrupt, is there a page you recommend for > anyone starting out in MariaDB development? Particularly any database or > MySQL internals material that help understand the codebase. That depends on what you're trying to do. There are two books: http://shop.oreilly.com/product/9780596009571.do http://www.packtpub.com/mysql-51-plugin-development/book There's MySQL internals manual: http://dev.mysql.com/doc/internals/en/index.html There's MariaDB Knowledge Base that includes pages about MariaDB internals: http://kb.askmonty.org/ There're numerous blog posts and presentations about specific topics. Regards, Sergei

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