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Re: 0520a00: MDEV-7964 - delete_dynamic() takes 0.12% in OLTP RO
On May 09, Sergey Vojtovich wrote:
> > > > Which may be fine, if MDL subsystem places only one lock in this
> > > > case (iirc, it does). But what is cheaper - collapse identical
> > > > schemas into one mdl request here (with Hash_set) or let mdl
> > > > sort it out later?
> > > MDL doesn't eliminate them, but rather clones compatible requests.
> > > Performance wise it will be slower in certain cases, but since
> > > this is DDL is performance that important?
> > If it isn't, why are you eliminating Hash_set?
> Because Hash_set was created for DML too. :(
I believe it's rather unusual to have DDL that involves many tables,
so fine, ok to push.