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Message #06756
Re: Rev 3967: MDEV-5597 - Reduce usage of LOCK_open: LOCK_flush
Hi, Sergey!
On Jan 31, Sergey Vojtovich wrote:
> >
> > I'm sorry, I don't understand that at all.
> >
> > Why my_refs is only incremented in debug builds? In non-debug builds you
> > wait until all tables but one are closed, in debug builds you may keep
> > more than one table opened.
> See above, this patch removes #ifndef DBUG_OFF, so my_refs are counted properly
> in both builds.
Right. Sorry. My mistake.
> > You wait here on a condition, how do you know there's FLUSH TABLES (or
> > anything at all) running that will signal this condition?
> 1. we're protected by exclusive metadata lock, so the only possible statement
> that may cause concurrency issues should be FLUSH TABLES (in fact there are
> more cases, like ha_table_exists()).
> 2. share->tdc.all_tables holds only tables owned by current thread (or empty),
> there are assertions for this above.
> 3. if concurrent FLUSH TABLES removed some TABLE instances from tdc.all_tables,
> but didn't close them yet, share ref_count reflects that.
> 4. this FLUSH TABLES must call intern_close_table(), which will eventually call
> tdc_release_share()/mysql_cond_broadcast().
>
> That's it.
Okay, thanks. Got it.
What did you mean "like ha_table_exists()" ?
Regards,
Sergei
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