1
vote
2answers
152 views

Why is MySQL not using the index with the higher cardinality?

I have an index called source with cardinality of 1122 and a second index called state with cardinality of 22. MySQL keeps using the state index when when query SELECT C1 FROM tbl WHERE source = 'x' ...
2
votes
2answers
186 views

Why does MySQL fail to use an index effectively when LIMIT offset is large?

I do not understand when querying 5 rows from a table of 500,000 rows, the following query takes 0.00sec: SELECT id, username FROM Users FORCE INDEX (PRIMARY) ORDER BY id LIMIT 20,5; But querying ...
1
vote
2answers
2k views

MySQL not responding, Writing to net status

I just had to reboot MySQL to regain access to some of my website. It had under 300MB of RAM used. Another product was working fine though, accessing it's own tables which are InnoDB. Here's the show ...
1
vote
0answers
175 views

How to speed up this query

MySQL doesn't have nearest neighbor search so. So I try to come up with a "distance" that's reasonable so the number of returned query is around 20-200. That way innodb doesn't have to compute ...
4
votes
2answers
4k views

Performance settings for MyISAM tables - keep everything in memory

I have a 8-core MySQL server with 32 GB of RAM, holding 40 MyISAM tables (total: ~4GB of data). Since the databases size is several times smaller than the available memory, how can I make full usage ...