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Note that adding comments to otherwise identical queries will typically cause the MySQL query cache to not realize they are the same. See: http://www.mysqlperformanceblog.com/2008/03/20/mysql-query-c...

Otherwise, neat idea, I like it.

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Most, if not all production mysql installations have this cache disabled anyways. (Based on my experience at Engine Yard for 3 years and other places the last 5 years.)

Why?

Mutex issues and other problems with high insert / update rates. Google "mysql query cache issues" and "mysql query cache disable" for lots of posts about the various costs / benefits.

Also the MySQL query cache is not very granular, it gets cleared on every write to that table. Thus, we've seen in practice that with it enabled MySQL has poorer performance as its constantly being flushed. The overhead of maintaining it doesnt pay off.

Of course its a trade-off. If you have have substantially more reads than writes than it might be OK for your needs.

I did not realize that. Interesting. Thanks!

I think if you just prepend C-style comments (e.g. /* test */ SELECT...) it should still work with the query cache [1]. But leading line comments (like --) will not work [2].

[1] http://bugs.mysql.com/bug.php?id=824

[2] http://bugs.mysql.com/bug.php?id=40986

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