Horton

Re: Alias collision in `refresh materialized view concurrently`

Michael Paquier <michael@paquier.xyz>

View thread View on postgr.es
From: Michael Paquier <michael@paquier.xyz>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>, Thomas Munro <thomas.munro@gmail.com>, Bernd Helmle <mailings@oopsware.de>, Mathis Rudolf <mathis.rudolf@credativ.de>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2021-08-07T01:40:47Z
Lists: pgsql-hackers 
On Fri, Aug 06, 2021 at 10:48:40AM -0400, Tom Lane wrote:
> AFAICT that works and generates the identical parse tree to the original
> coding.  The only place touched by the patch where it's a bit difficult to
> make the syntax unambiguous this way is
> 
>                     "CREATE TEMP TABLE %s AS "
>                     "SELECT _$mv.ctid AS tid, _$newdata "
>                     "FROM %s _$mv FULL JOIN %s _$newdata ON (",
> 
> because newdata.* would ordinarily get expanded to multiple columns
> if it's at the top level of a SELECT list, and that's not what we want.
> However, that's easily fixed using the same hack as in ruleutils.c's
> get_variable: add a no-op cast to the table's rowtype.  So this
> would look like
> 
>     appendStringInfo(&querybuf,
>                      "CREATE TEMP TABLE %s AS "
>                      "SELECT mv.ctid AS tid, newdata.*::%s "
>                      "FROM %s mv FULL JOIN %s newdata ON (",
>                      diffname, matviewname, matviewname, tempname);

Smart piece.  I haven't thought of that.

> Given that it took this long to notice the problem at all, maybe
> this is not a fix to cram in on the weekend before the release wrap.
> But I don't see why we need to settle for "mostly works" when
> "always works" is barely any harder.

Yes, I would vote to delay that for a couple of days.  That's not
worth taking a risk for.
--
Michael

Commits

  1. Really fix the ambiguity in REFRESH MATERIALIZED VIEW CONCURRENTLY.

  2. Reduce risks of conflicts in internal queries of REFRESH MATVIEW CONCURRENTLY