Re: Slooooow query in MySQL.

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Chris wrote:
Rob Adams wrote:
I have a query that I run using mysql that returns about 60,000 plus rows. It's been so large that I've just been testing it with a limit 0, 10000 (ten thousand) on the query. That used to take about 10 minutes to run, including processing time in PHP which spits out xml from the query. I decided to chunk the query down into 1,000 row increments, and tried that. The script processed 10,000 rows in 23 seconds! I was amazed! But unfortunately it takes quite a bit longer than 6*23 to process the 60,000 rows that way (1,000 at a time). It takes almost 8 minutes. I can't figure out why it takes so long, or how to make it faster. The data for 60,000 rows is about 120mb, so I would prefer not to use a temporary table. Any other suggestions? This is probably more a db issue than a php issue, but I thought I'd try here first.

Sounds like missing indexes or something.

Use explain: http://dev.mysql.com/doc/refman/4.1/en/explain.html

If that were the case I wouldn't expect limiting the number of rows returned to make a difference since the actual query is the same.

Chances are it's purely a data transfer delay. Do a test with the same query but only grab one of the fields - something relative small like a integer field - and see if that's significantly quicker. I'm betting it will be.

If that is the problem you need to be looking at making sure you're only getting the fields you need. You may also want to look into changing the cursor type you're using although I'm not sure if that's possible with MySQL nevermind how to do it.

-Stut

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