… count was much faster – MySQL accessed our table data when calculated result set size even when this was not needed (after… index scan inly which is much faster here. Just to be objective I’ve tried to perform this test without indexes (full scan) and with index on b column. Results were following: Full-scan: 7 seconds for SQL_CALC…
Post: Multi Range Read (MRR) in MySQL 5.6 and MariaDB 5.5
March 21, 2012 By 10 Comments
…value fetched from step 1, and when the buffer is full sort them by pk_column, and do a range …read 799239 914146 912318 914146 912318 Select_scan 1 1 1 1 1 Sort_scan 1 1 1 1 1 As … Probably its due to a bug in how counter is calculated inside MariaDB? Other Observations Sometimes both for MariaDB 5.5…
Post: Indexes in MySQL
June 2, 2006 By 29 Comments
… a full table scan is preferable than an index access. As far as I know Oracle alway chooses a full table scan if selectivity… compare the execution time with index access and with table scan: SELECT COUNT(SUBNAME) FROM t2 WHERE ID1=1 – 410 ms… That is table scan is faster by 4.6 times. Why does MySQL choose index access? MySQL doesn’t calculate index selectivity…
Post: How Percona does a MySQL Performance Audit
November 24, 2008 By 17 Comments
…experience, not a recipe that anyone can follow. A full performance audit is far more extensive than this …without polluting my brain with that. I’ll just scan this for anything odd. In contrast to what …possible to improve a lot, and a simple mental calculation can then tell me how much total gain I…
Post: SHOW INNODB STATUS walk through
July 17, 2006 By 40 Comments
…===================================== 060717 3:07:56 INNODB MONITOR OUTPUT ===================================== Per second averages calculated from the last 44 seconds Make sure data is… these should be 16K – page size, for full table scan or index scan read-ahead may be performed which can increase…
Post: Announcing Percona Server 5.5.27-29.0
October 11, 2012 By Leave a Comment
… implementing faster incremental backups that use this information to avoid full data scans. Number of binlog files can be restricted when using… hash index. Fixed by changing the way partition sizes are calculated initially. Bug fixed #1018264 (George Ormond Lorch III). Postfix would…
