Wednesday, June 16, 2010

quick update from down under...

I'm pleased to report that so far the Soccer World Cup has been pulled off rather successfully, with only minor incidents reported. I have however noticed local news showing some 'feel-good' stories that are obviously written to give a false impression to the international media of the real situation here. Let's hope the unions and Eskom workers don't mess things up by holding a gun to the Country's head with protesting/striking too much in the international media's light.. Hold thumbs..

BTW, I hate the vuvuzela :)

I thought I should share two important MySQL bugs with you today. In case you ever used YaSSL to establish SSL connections, you were at risk of hitting random crashes due to bug #34236 (Various possibly related SSL crashes) if more than one concurrent connection was ever made. The reason is the YaSSL code was built without mutexes as if for single threaded apps...

Next bug I think is widespread enough to mention is optimizer/query plan related. Examine the testcase on bug #48537 (difference of index selection between rpm binary and .tar.gz, windows vs linux..) And read the changeset notes:

On Intel x86 machines index selection by the MySQL query
optimizer could sometimes depend on the compiler version and
optimization flags used to build the server binary.

The problem was a result of a known issue with floating point
calculations on x86: since internal FPU precision (80 bit)
differs from precision used by programs (32-bit float or 64-bit
double), the result of calculating a complex expression may
depend on how FPU registers are allocated by the compiler and
whether intermediate values are spilled from FPU to memory. In
this particular case compiler versions and optimization flags
had an effect on cost calculation when choosing the best index
in best_access_path().

A possible solution to this problem which has already been
implemented in mysql-trunk is to limit FPU internal precision
to 64 bits. So the fix is a backport of the relevant code to
5.1 from mysql-trunk.

Now I'll get back to enjoying the public holiday and bugs reporting ;-)

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