July 2012 - discuss - lists.mariadb.org

[Maria-discuss] explain for insert/update/delete
by MARK CALLAGHAN 08 Jul '25

08 Jul '25

Does MariaDB have any plans to support explain for insert/update/delete/replace/CTAS? There have been feature requests open for a very long time on official MySQL without any progress. I have had a few problems in production from 'bad' delete statements that had a very different plan than the select statement with the same where clause. The only way to check for a bad plan today is to use SHOW INNODB STATUS to determine whether the statement locks all rows in a table. http://bugs.mysql.com/bug.php?id=14745 http://bugs.mysql.com/bug.php?id=35355 -- Mark Callaghan mdcallag(a)gmail.com

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[Maria-discuss] Did we drop source for IBMDB2I?
by Colin Charles 28 Jul '12

28 Jul '12

Hi! Reading: http://kb.askmonty.org/en/mariadb-versus-mysql-features/ "IBMDB2I. Oracle removed this in MySQL 5.1.55 but we have kept the code in MariaDB until the version 5.5." I'm not so sure. I looked for this engine in a 5.5.25 tarball in storage/ and didn't see it. It is in 5.3 tree trunk, but not 5.5 Is this an oversight? Or have we decided to remove the engine? Thanks -- Colin Charles, http://bytebot.net/blog/ | twitter: @bytebot | skype: colincharles MariaDB: Community developed. Feature enhanced. Backward compatible. Download it at: http://www.mariadb.org/ Open MariaDB/MySQL documentation at the Knowledgebase: http://kb.askmonty.org/

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[Maria-discuss] KB Question: GROUP BY trick has been optimized away
by Daniel Bartholomew 23 Jul '12

23 Jul '12

The following question has been posted to the Knowledgebase: https://kb.askmonty.org/en/group-by-trick-has-been-optimized-away/ - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - GROUP BY trick has been optimized away Group-by trick example: Find the most populous city in each state: SELECT state, city, population, COUNT(*) AS num_cities FROM ( SELECT state, city, population FROM us ORDER BY state, population DESC ) p GROUP BY state ORDER BY state; +-------+-------------+------------+------------+ | state | city | population | num_cities | +-------+-------------+------------+------------+ | AK | Anchorage | 276263 | 16 | | AL | Birmingham | 231621 | 58 | | AR | Little Rock | 184217 | 40 | | AZ | Phoenix | 1428509 | 51 | | CA | Los Angeles | 3877129 | 447 | ... That was the output in MySQL 5.1. But with MariaDB 5.5.23, I get: +-------+-------------------+------------+------------+ | state | city | population | num_cities | +-------+-------------------+------------+------------+ | AK | Anchorage | 276263 | 16 | | AL | Alabaster | 26738 | 58 | | AR | Arkadelphia | 11062 | 40 | | AZ | Apache Junction | 34904 | 51 | | CA | Adelanto | 21955 | 447 | ... The EXPLAIN plan do longer shows a subquery, as if the inner ORDER BY has been thrown away. Granted, there is nothing in the definition of MySQL (much less in the SQL standard) that requires that Los Angeles should be bigger than Adelanto. But the replacement code for this 'trick' is quite messy. Am I correct in deducing (from the outside, looking in) that MariaDB's optimizations are the cause of the change? - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Thanks. -- Daniel Bartholomew Google+ - http://gplus.to/dbart Twitter - http://twitter.com/daniel_bart MariaDB: An Enhanced Drop-in Replacement for MySQL Website - http://mariadb.org Twitter - http://twitter.com/mariadb Google+ - http://gplus.to/mariadb Facebook - http://fb.com/MariaDB.dbms Knowledgebase - http://kb.askmonty.org Monty Program - http://montyprogram.com

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[Maria-discuss] KB Question: DROP TABLE Syntax Causing Memory Leak
by Daniel Bartholomew 23 Jul '12

23 Jul '12

The following question has been posted to the Knowledgebase: https://kb.askmonty.org/en/drop-table-syntax-causeing-memory-leak/ - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - DROP TABLE Syntax Causing Memory Leak I have a Server with 2 Xeon E5645 total 12cores and 24 threads on a X8DAH+-F-B Motherboard and 96Gigs of Memory and 4 Terabytes of hard drive space. We are running the newest stable release of MariaDB 5.5.25. every night I run a PHP script to bring a large data set roughly 500K records or so into a XtraDB Table I use as a "SWAP" table. I processing,filtering, massaging the data in this table then insert this processed data into other tables where it can be accessed by a web application. At the end of this Script I DROP this "SWAP" table. This Script runs 24 times a day and does not seem to have much issues. But For Some reason seemingly randomly the DROP table Command while checking permissions to drop the Table will lockup the database. I have tried truncate too and it seems to have the same issue. The innodb_buffer_pool_size=35G. Any Ideas what the problem could be or where to start looking? Noctechie - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Thanks. -- Daniel Bartholomew Google+ - http://gplus.to/dbart Twitter - http://twitter.com/daniel_bart MariaDB: An Enhanced Drop-in Replacement for MySQL Website - http://mariadb.org Twitter - http://twitter.com/mariadb Google+ - http://gplus.to/mariadb Facebook - http://fb.com/MariaDB.dbms Knowledgebase - http://kb.askmonty.org Monty Program - http://montyprogram.com

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