0
votes
1answer
421 views

MySQL query optimizer ignoring smaller scan on TIMESTAMP column, cardinality?

I've got a complex multi-join query where the optimizer won't pick an index on a TIMESTAMP column even though it results in a smaller index/table scan. If I force the index on the TIMESTAMP column, ...
6
votes
2answers
200 views

Is there any way to trace optimizer's work in MySQL?

Just like the MEMO structure in SQL Server which is kind of a "paper trail" of steps the optimizer takes in optimizing the query. Is there anything in MySQL through which I can get the information ...
1
vote
1answer
643 views

Will OPTIMIZE TABLE have any impact on my data?

I'm having issues with a database that is getting quite slow. The analyzer in phpMyAdmin recommends that I run OPTIMIZE TABLE on my tables. But before doing so, I would (of course) like to know if ...
1
vote
1answer
2k views

MySQL optimization

I'm trying to optimize a MySQL Server to be able to serve as many connections as it can. The server is in AmazonAWS RDS and has currently the following resources: --7.5 GB memory, 4 ECUs (2 ...
4
votes
2answers
1k views

Is there a way to hint to query optimizer to MySQL which constraints should be done first?

This is my current query: SELECT BusinessID as ID, 111151.29341326*SQRT(pow(-6.186751-X(LatLong),2)+pow(106.772835-Y(LatLong),2)*0.98838574205337) AS Distance from ( SELECT * FROM ...
3
votes
1answer
195 views

How does the MySQL Query Optimizer react to a SELECT COUNT sentence?

Let's say we have a table called "customers" with these columns ("id", "name", "country", "created_at). There's an index by ("country", "created_at"). If SELECT COUNT(*) FROM customers WHERE ID ...
4
votes
1answer
2k views

Mysql Memory table getting many locks

On my site I log every pageview (date, ip, referrer, page, etc) in a simple mysql table. This table has the following activity: 1 SELECT per minute 1 DELETE per minute no UPDATE queries Lots of ...
6
votes
1answer
1k views

Using FORCE INDEX

I was in a presentation recently given by a Facebook MySQL engineer and he mentioned there that using FORCE INDEX reduces I/O. It was something to do with the MySQL Query Optimizer not needing to go ...