… is indexes. If you add multiple multi-column indexes the difference with InnoDB will be even more notable. Also it allows multiple clustering indexes that… and 4.x). It really shines on large tables and index scan like queries.
Post: Is Synchronous Replication right for your app?
May 14, 2013 By 18 Comments
… is a single row (well, the PRIMARY KEY index entry for that row). This means typically on …. This is not implemented for full BEGIN … COMMIT multi-statement transactions since it cannot be assumed that …In Example 2, above, how above moving the ‘joined’ column to the users_groups table so we don’…
Post: Multi Column indexes vs Index Merge
September 19, 2009 By 31 Comments
… have combined multi-column index on (AGE,STATE). Lets see why it is the case. MySQL indexes are (with few exceptions) BTREE indexes – this index type… index merge indeed improves performance compared to single index only but it is by far better to use multi column indexes. But the problems with Index…
Post: Multi-Column IN clause - Unexpected MySQL Issue
April 4, 2008 By 21 Comments
… massive amount of urls. To save on indexes instead of using URL we index CRC32 of the URL which allows to find… missing optimizer feature. I should not be surprised though as multi-column in is not the most used MySQL feature out there… case we could simply rewrite query using more standard single column IN clause: mysql> explain SELECT url FROM 106pages.106pages WHERE…
Post: 3 ways MySQL uses indexes
September 12, 2009 By 28 Comments
… is not index prefix. It is important to look at key_len column in explain plan to see how many index parts are actually used for row lookup. Very common problem I see is multi column indexes… to couple of columns index can be simply much smaller than the data which is one of the reason covering indexes help to…
Comment: How to find wrong indexing with glance view
August 22, 2008 By 27 Comments
… a few columns from that index without losing any performance. And there’s the problem of mysql choosing single column indexes where multi-column indexes are present, and wasting memory and disk space. I still think that single column indexes make more sense…
Comment: How to find wrong indexing with glance view
August 22, 2008 By 27 Comments
… definitely want to keep those 3 additional columns in your index. When that 4th extra column moves from millions to 20 records, it… situation. I will agree with tgabi, most of the time multi-column indexes are not necessary. If you’re not having issues then… to help others by making aware reasons for particular solutions (multi-column index in this case) in MySQL.
Comment: How to find wrong indexing with glance view
August 22, 2008 By 27 Comments
… said:”in case there is good cardinality on both columns and full index can be used”. I’d call that a “best…, yet each column has only few values.Sometimes I wish I can find a multi-column index that works. I have few multi-column that do work, particular when used for ordering (ORDER BY a,b LIMIT 5). Index…
Post: Index Condition Pushdown in MySQL 5.6 and MariaDB 5.5 and its performance impact
March 12, 2012 By 12 Comments
… this blog post is aimed at a new optimizer enhancement Index Condition Pushdown (ICP). Its available in both MySQL 5.6… is, and what is it aimed at. Index Condition Pushdown Traditional B-Tree index lookups have some limitations in cases such as range scans, where index parts after the part on which range condition is applied…
Comment: How to find wrong indexing with glance view
August 22, 2008 By 27 Comments
… Will only use only first column of multiple column index in case you have Range on the first column like col1 BETWEEN 5 and 10 – it is exactly skill of creating multi column indexes… a lot of difference) Saying MySQL can’t use multiple column indexes is simular to saying MySQL always does full table scan…
