Horton

Re: Allow CLUSTER, VACUUM FULL and REINDEX to change tablespace on the fly

Alvaro Herrera <alvherre@alvh.no-ip.org>

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From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: Alexey Kondratov <a.kondratov@postgrespro.ru>
Cc: Michael Paquier <michael@paquier.xyz>, Justin Pryzby <pryzby@telsasoft.com>, Peter Eisentraut <peter.eisentraut@enterprisedb.com>, Masahiko Sawada <masahiko.sawada@2ndquadrant.com>, Steve Singer <steve@ssinger.info>, pgsql-hackers@lists.postgresql.org, Robert Haas <robertmhaas@gmail.com>, Alexander Korotkov <a.korotkov@postgrespro.ru>, Masahiko Sawada <sawada.mshk@gmail.com>, Jose Luis Tallon <jltallon@adv-solutions.net>
Date: 2021-01-27T21:36:58Z
Lists: pgsql-hackers 
On 2021-Jan-28, Alexey Kondratov wrote:

> I have read more about lock levels and ShareLock should prevent any kind of
> physical modification of indexes. We already hold ShareLock doing
> find_all_inheritors(), which is higher than ShareUpdateExclusiveLock, so
> using ShareLock seems to be safe here, but I will look on it closer.

You can look at lock.c where LockConflicts[] is; that would tell you
that ShareLock indeed conflicts with ShareUpdateExclusiveLock ... but it
does not conflict with itself!  So it would be possible to have more
than one process doing this thing at the same time, which surely makes
no sense.

I didn't look at the patch closely enough to understand why you're
trying to do something like CLUSTER, VACUUM FULL or REINDEX without
holding full AccessExclusiveLock on the relation.  But do keep in mind
that once you hold a lock on a relation, trying to grab a weaker lock
afterwards is pretty pointless.

-- 
Álvaro Herrera                            39°49'30"S 73°17'W
"E pur si muove" (Galileo Galilei)

Commits

  1. Add TABLESPACE option to REINDEX

  2. Refactor code in tablecmds.c to check and process tablespace moves

  3. Refactor option handling of CLUSTER, REINDEX and VACUUM

  4. pg_dump: Don't use enums for defining bit mask values

  5. Refactor CLUSTER and REINDEX grammar to use DefElem for option lists

  6. Refactor parsing rules for option lists of EXPLAIN, VACUUM and ANALYZE

  7. Improve tab completion of REINDEX in psql

  8. Fix possible crash during FATAL exit from reindexing.