Why one reading query lock another one?

[Yan Yan]

Hi all,

When I do some query join the tables with MyISAM engine. The select query entered into the "copying to tmp table" status, MySQL will use the filesort. Then other queries(they are all the reading query) will be locked by this one.

Of course, we should do some optimizationes to avoid this case.

But I just want to know why one select query locked another select query.( As I know, the lock for reading should not affect the ohter reading)

thanks for your help!