Re: refresh materialized view concurrently

On 2013-07-03 11:08:32 -0400, Tom Lane wrote:
> Robert Haas <robertmhaas@gmail.com> writes:
> > On Wed, Jul 3, 2013 at 10:47 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> >> Are we somehow not going through ExecOpenIndices?
> 
> > I dunno.  I just did a quick black-box test:
> 
> > CREATE TABLE foo (a int primary key);
> > BEGIN;
> > INSERT INTO foo VALUES (1);
> > SELECT relation::regclass, locktype, mode, granted FROM pg_locks;
> 
> > I get:
> 
> >  relation |   locktype    |       mode       | granted
> > ----------+---------------+------------------+---------
> >  pg_locks | relation      | AccessShareLock  | t
> >  foo      | relation      | RowExclusiveLock | t
> >           | virtualxid    | ExclusiveLock    | t
> >           | transactionid | ExclusiveLock    | t
> 
> > No foo_pkey anywhere.
> 
> That proves nothing, as we don't keep such locks after the query
> (and there's no reason to AFAICS).  See ExecCloseIndices.

Should be easy enough to test by hacking LOCK TABLE to lock indexes and
taking out a conflicting lock (SHARE?) in a second transaction. I wonder
if we shouldn't just generally allow that, I remember relaxing that
check before (when playing with CREATE/DROP CONCURRENTLY afair).

Greetings,

Andres Freund

-- Andres Freund                       http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training &
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