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Re: Select count very slow
Posted by: Peter Brawley
Date: May 22, 2017 11:24AM

In a transactional table, count(*) entails actual row counting, so in big tables it's necessarily slow.

If an estimate is good enough, pick up the row count value from the 5th row of SHOW TABLE STATUS FROM yourdb WHERE name=yourtable.

If an exact count is needed quickly, you can create your own stats table and write insert & delete triggers to update it. Beware that Drop/Create and Truncate will require that you zero your stored rowcount.

Your 2nd instance goes with default InnoDB settings. Did you test count(*) with default settings on the first server?

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