Query problem

[Patrick Neeley]

I've got a table (I'll call it matchTable for this example) with 7 million records and growing rapidly. Has cols tableA_ID and tableB_ID (both are mediumints), and item_1 through item_n (tinyints with value 0 or 1). tableA_ID and tableB_ID have a keyed (combined) indexed.

I run a query that looks like this:

SELECT DISTINCT tableB_ID FROM matchTable WHERE tableA_ID IN(12,16,20,20030,254177)

My PHP page load stats tell me the script spends ~8 out the 11 total seconds (that it takes to run the entire script) doing MySQL queries... and it says that it's doing 201 of them. This is a problem as there are less than a dozen queries in the script, and less than 20 TOTAL queries are performed in the code (looped and all) in any one test run (yes, I'm sure of this.)

QUESTION 1: Does anyone know where these extra queries are coming from?

QUESTION 2: What will help? I can up the memory limits for MySQL if you think it's running out (but please tell me how I can check this.)

I really really need suggestions. This is a very complex system, the code is 100%, so I need the DB to be 100% also.

Thanks,
~ dr.p