…Server by converting the affected tables or columns to the collations introduced: utf8_general_ci… / #51196 and #61790 in MySQL (Alexey Kopytov). Uninitialized values in the Slow Query Log patch. Bug …: #803865 (Laurynas Biveinis). Using the innodb_lazy_drop_table option led to an assertion error…
Post: Improved InnoDB fast index creation
November 6, 2011 By 4 Comments
… could be faster if secondary indexes were temporarily dropped and then recreated using fast index creation; … mysql> SET profiling=1; Query OK, 0 rows affected (0.00 sec) mysql> ALTER TABLE t ADD COLUMN …table” part will not be affected by a slow tmpdir, but rebuilding the indexes will obviously take…
Post: Heikki Tuuri Innodb answers - Part I
October 26, 2007 By 19 Comments
…the pessimistic delete, if the page data size drops below this limit, merging it to… having to seek on disk which slows down throughput. If we could control… ha_innodb.cc in 5.1: static MYSQL_SYSVAR_ULONG(thread_concurrency, srv_thread_…it can be used if the columns are the first columns in an index. I…
Comment: Why MySQL could be slow with large tables ?
January 31, 2008 By 141 Comments
… working on a web project using MySql, Apache and Php. The database has …. After those months pass, I’ll drop all those tables, and rebuild them …for the last capital letter column, because I use that column to filter in the table… from it?! Could the INSERTs be slow, dued to the size of the PRIMARY…
Post: Thinking about running OPTIMIZE on your Innodb Table ? Stop!
December 9, 2010 By 18 Comments
…in very random order, such as indexes on UUID column or something similar. It also produces a lot …mysql> alter table a drop key c; Query OK, 0 rows affected (0.46 sec) Records: 0 Duplicates: 0 Warnings: 0 mysql… not get advantage of it and will use old slow method of building indexes by insertion…
Post: Using CHAR keys for joins, how much is the overhead ?
June 18, 2007 By 18 Comments
…MyISAM uses key compression for varchar columns so random key lookups become significantly … this to shorten some internal buffers MySQL has to allocate for key … to check if using longer strings slows down things significantly and so …me much longer keys. The performance dropped down to 6.1 seconds …
Comment: Four ways to optimize paginated displays
October 17, 2008 By 27 Comments
…execute. The SELECT portion of the query was specifying which columns to fetch (i.e. SELECT table.col2, table.col2, … table… the query time dropped to 0.01 sec.! So, in the end, it did not appear that the slowness was a result…query optimization path for the two forms of query either. MySQL bug? Sam
Post: Using LoadAvg for Performance Optimization
December 4, 2006 By 5 Comments
…like moving average of sum of “r” and “b” columns from VMSTAT. Obviously minimum value for LoadAvg is … run single batch job on the server with MySQL, Load Average is likely to be close to …drops. This is however temporary relive only as there are stubborn users which would not go away even with slow…
Post: Drilling down to the source of the problem
November 8, 2008 By 7 Comments
… to complete, with progress almost paused (dropping from thousands to tens of queries per… on this lock, suggest upgrading to MySQL 5.1 and call it a day… which did not have auto-increment columns and general updates. The stall was … a false one – because single insert slows down a lot of inserts pile …
