… answers: Q: Can you compare the use of subqueries/multiple joins vs. multiple queries (e.g. temp tables)? For performance, it’s… tradeoff of this solution is that it requires storing another column, and reinitializing the sequence after making certain insert/update/delete… against multiple columns in a compound index, then the order would matter, and it would have to match the order of columns in the index…
Comment: Benchmarking Percona Server TokuDB vs InnoDB
May 7, 2013 By 32 Comments
… TokuDB 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
…Innodb is a single row (well, the PRIMARY KEY index entry for that row). This means typically on a…It does NOT mean you can’t modify data on multiple cluster nodes simultaneously. You can. It does NOT set…In Example 2, above, how above moving the ‘joined’ column to the users_groups table so we don’t…
Post: Multiple column index vs multiple indexes
August 22, 2008 By 13 Comments
… about Index Merge on Multiple Indexes vs Two Column Index efficiency. I mentioned in most cases when query can use both of the ways using multiple column index…: For benchmarked queries we can see Multiple Column index beats Index Merge in all cases when such index can be used. It is also worth…
Post: The Optimization That (Often) Isn't: Index Merge Intersection
December 14, 2012 By 6 Comments
… with columns that had single-column indexes on them, MySQL could sometimes make use of the multiple indexes. For instance, “SELECT foo FROM bar WHERE indexed_colA = X OR indexed…
Post: Multi Column indexes vs Index Merge
September 19, 2009 By 31 Comments
… Index merge works much better than multiple column indexes. This is in case you’re using OR between the columns. In this case the combined index… combined index in this case. In case you’re using OR between columns – single column indexes are required for index merge to work and combined indexes…
Post: Find and remove duplicate indexes
June 20, 2012 By 9 Comments
… indexes and how to find and remove them. Duplicate keys on the same column This is the easiest one. You can create multiple indexes on the same column and MySQL won’t complain. Let’s see this example: mysql> alter table t add index(name…
Post: How to find wrong indexing with glance view
August 21, 2008 By 27 Comments
…. If you have queries with multiple column restrictions in WHERE clause you most likely will need to have multiple column indexes for optimal performance. But wait. Do not go ahead and index all combinations. This would likely…
Post: Should you name indexes while doing ALTER TABLE ?
May 28, 2008 By 10 Comments
… the indexes. Lets first speak about naming. If you do not specify index name MySQL will name index by the first column of index created, if there is such index already it will… names are not really helpful for multiple column indexes – you can’t easily see what is the index MySQL trying to use from explain…
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… using multiple column IN makes MySQL to pick doing full table scan in this case, even though the cardinality on the first column… case we could simply rewrite query using more standard single column IN clause: mysql> explain SELECT url FROM 106pages.106pages WHERE…
