Re: remove spurious CREATE INDEX CONCURRENTLY wait

On Mon, Nov 09, 2020 at 04:47:43PM +0100, Dmitry Dolgov wrote:
> > On Tue, Nov 03, 2020 at 07:14:47PM +0100, Dmitry Dolgov wrote:
> > > On Thu, Aug 20, 2020 at 03:11:19PM +0900, Michael Paquier wrote:
> > > On Wed, Aug 19, 2020 at 02:16:46PM -0400, Alvaro Herrera wrote:
> > > > I did not set the flag in REINDEX CONCURRENTLY, but as I understand it
> > > > can be done too, since in essence it's the same thing as a CIC from a
> > > > snapshot management point of view.
> > >
> > > Yes, I see no problems for REINDEX CONCURRENTLY as well as long as
> > > there are no predicates and expressions involved.  The transactions
> > > that should be patched are all started in ReindexRelationConcurrently.
> > > The transaction of index_concurrently_swap() cannot set up that
> > > though.  Only thing to be careful is to make sure that safe_flag is
> > > correct depending on the list of indexes worked on.
> >
> > Hi,
> >
> > After looking through the thread and reading the patch it seems good,
> > and there are only few minor questions:
> >
> > * Doing the same for REINDEX CONCURRENTLY, which does make sense. In
> >   fact it's already mentioned in the commentaries as done, which a bit
> >   confusing.
> 
> Just to give it a shot, would the attached change be enough?

Could it be possible to rename vacuumFlags to statusFlags first?  I
did not see any objection to do this suggestion.

> +		LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
> +		MyProc->vacuumFlags |= PROC_IN_SAFE_IC;
> +		ProcGlobal->vacuumFlags[MyProc->pgxactoff] = MyProc->vacuumFlags;
> +		LWLockRelease(ProcArrayLock);

I can't help noticing that you are repeating the same code pattern
eight times.  I think that this should be in its own routine, and that
we had better document that this should be called just after starting
a transaction, with an assertion enforcing that.
--
Michael