| From: | Kevin Grittner <kgrittn(at)ymail(dot)com> |
|---|---|
| To: | Andres Freund <andres(at)2ndquadrant(dot)com>, Hitoshi Harada <umi(dot)tanuki(at)gmail(dot)com> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: refresh materialized view concurrently |
| Date: | 2013-06-27 14:25:12 |
| Message-ID: | 1372343112.77919.YahooMailNeo@web162905.mail.bf1.yahoo.com |
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| Lists: | pgsql-hackers |
Andres Freund <andres(at)2ndquadrant(dot)com> wrote:
> We can play cute tricks akin to what CREATE INDEX CONCURRENTLY currently
> does, i.e. wait for all other relations that could have possibly seen
> the old relfilenode (they must have at least a share lock on the
> relation) before dropping the actual storage.
>
> The reason we cannot currently do that in most scenarios is that we
> cannot perform transactional/mvcc updates of non-exclusively locked
> objects due to the SnapshotNow problems of seeing multiple or no
> versions of a row during a single scan.
Not only would that be slower than the submitted patch in cases
where only a few rows differ, but it could be waiting to swap in
that new heap for an unbounded amount of time. I think the current
patch will "play nicer" with incremental maintenance than what you
suggest here.
--
Kevin Grittner
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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