… (within a single connection) anywhere in any ‘free’ variant of MySQL. PARTITIONs are scanned one at a time. (Please provide specific… involves (1) find partition (if partitioned), (2) drill down the BTree, (3) remove one record. PARTITIONing makes very little difference. * If… two points. * Secondary indexes are also BTrees, so they need updating (although delayed). Yes, their BTrees may be one level shallower when…
Post: 3 ways MySQL uses indexes
September 12, 2009 By 28 Comments
… added on the first place. Most popular index type in MySQL – BTREE can speed up equality and prefix range matches. So if… of this mistakes come from missing one very important MySQL limitation – once MySQL runs into the interval range it will not use… require a bit more than simple range scan in the BTREE and MySQL decides to pass it on. There are some workarounds…
Post: MySQL Indexing Best Practices: Webinar Questions Followup
August 16, 2012 By 4 Comments
… key significantly fragmented. I also would note there are some MySQL optimizer restrictions in how well it can deal with primary… when using a CMS where DB structure is prepdefined A: MySQL Server will not automatically define any indexes for you. Hopefully… requirement for ORDER BY DESC optimization – you can still traverse BTREE in any direction, even if there are no page leaf…
Post: MySQL Partitioning - can save you or kill you
December 11, 2010 By 45 Comments
I wanted for a while to write about using MySQL Partitioning for Performance Optimization and I just got a relevant … slower. The gain from updates typically comes from having smaller BTREE on the active partition(s) which allows for a lot… prefix very well effectively giving almost uniform access to all BTREE. To solve this problem partitioning was a good choice – PARTITION…
Post: Performance gotcha of MySQL memory tables
February 1, 2008 By 5 Comments
… it is the only MySQL storage engine which defaults to HASH index type by default, instead of BTREE which makes indexes unusable… directly used for lookup. Changing the key c to be BTREE we instantly get about 15000 of deletes per second which…
Post: MySQL EXPLAIN limits and errors.
July 24, 2006 By 6 Comments
… query execution, sometimes being dynamic based on data. With EXPLAIN MySQL kind of simulates execution but it obviously does not access… it could be. If number of rows is estimated performing btree dive with certainly structured tree you still can get number… how many rows will be examined MySQL will still print full number. Here is example: mysql> explain select * from lt limit 10…
Post: Working with large data sets in MySQL
July 5, 2007 By 12 Comments
What does working with large data sets in mySQL teach you ? Of course you have to learn a lot … got to learn when working with large data things in MySQL is patience and careful planning. Both of which relate two… decent performance. Typically it would be some portion of Index BTREE (even MyISAM which builds “normal” indexes by sort builds primary…
Post: ANALYZE: MyISAM vs Innodb
September 3, 2008 By 9 Comments
… | YES | BTREE | | | antest_innodb | 1 | c | 2 | i | A | 20491 | NULL | NULL | | BTREE | | +—————+————+———-+————–+————-+———–+————-+———-+——–+——+————+———+ 3 rows in set (0.00 sec) mysql> analyze table… | NULL | YES | BTREE | | | antest | 1 | c | 2 | i | A | 245760 | NULL | NULL | | BTREE | | +——–+————+———-+————–+————-+———–+————-+———-+——–+——+————+———+ 3 rows in set (0.00 sec) mysql> analyze table…
Comment: ORDER BY ... LIMIT Performance Optimization
November 17, 2009 By 100 Comments
… | userid | A | NULL | NULL | NULL | | BTREE | | | follow | 0 | PRIMARY | 2 | followuserid | A | 63537 | NULL | NULL | | BTREE | | +——–+————+———-+————–+————–+———–+————-+———-+——–+——+————+———+ mysql> show index from posts…
Post: Predicting how long data load would take
May 24, 2007 By 14 Comments
… it progresses it may slow down dramatically, typically if Index BTREE has to be built by insertion and data does not… powerful box and copy it back in a binary form. MySQL Configuration Different storage engines have different settings which need to… Load Options There two main ways to load data in MySQL you can use Multiple value insert (standard mysqldump output) or…
