MySQL Performance Blog

Sometimes due to programming error or due to very complex query you can get your PHP script running too long, well after user stopped waiting for the page to render and went browsing other sites.
Looking at Server-Status I’ve seen scripts executing for hours sometimes which is obviously the problem – they take Apache Slot, MySQL Connection and other resources.

I had discussion today who was thinking Apache would kill the script after “Timeout” specified in Apache configuration is reached – this was not my experience so I decided to run couple of tests to check it.

I wrote couple of very simple scripts which demonstrate different behavior for scripts running very long time. For simplicity I did not use MySQL, but other system call – sleep() which has similar behavior for sake of experiment:

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Remembering that I did RENAME DATABASE in MySQL 5.1.21 and found it useful I tried it with 5.1.24 (I was playing with 20GB InnoDB database, so dumping is not fastest way) and all my tries finished with “Syntax error”.
So RTMF and documentation says
“This statement was added in MySQL 5.1.7 but was found to be dangerous and was removed in MySQL 5.1.23.”

For me term ‘dangerous’ is interesting there , as I’d expect really dangerous is DROP DATABASE (which I hope will not be removed in next release) , and RENAME DATABASE is supposed to be kind of safe – just replaces old name to new one.

I guess there are some related bugs – and there are:
Bug#28360: RENAME DATABASE destroys routines
Bug#17565: RENAME DATABASE destroys events
so basically RENAME DATABASE destroyed all events and routines related to database.

And solution of bug is:

Removed the
RENAME DATABASE db1 TO db2
statement.

So it seems MySQL took an interesting practice to get GA released as soon as possible – just remove features that does not work instead of fix it.
The similar was with FEDERATED storage engine, which was disabled by default in 5.1.23 binaries, in contrast to previous version (but should be enabled again in 5.1.24).

That probably helps to get ‘Zero P1 bugs reported’