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Posted in "cache"

MySQL, bad preformance of INFORMATION_SCHEMA queries

cache mysql performance php

Recently I've discovered a quite big perfomance problem when running INFORMATION_SCHEMA queries on mysql.

In particular I found that on some systems (some mysql versions) a query like

SELECT * FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_SCHEMA = 'db_name' AND TABLE_NAME = 'db_table'

can take up to 0.1s to run!

Clearly such time interval is not acceptable, and I think it happens only with some versions of mysql because I've run some tests on my local machine and on the server where this site is running obtaining a result of 0.0007 seconds, we are talking about a difference of two orders of magnitude!

I've not investigated more about which mysql versions are affected and if there are any patches, I ...

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