From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: Michael Paquier <michael@paquier.xyz>
Cc: Justin Pryzby <pryzby@telsasoft.com>
Cc: Amit Langote <amitlangote09@gmail.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgsql-hackers@postgresql.org
Subject: Re: ALTER tbl rewrite loses CLUSTER ON index
Date: Thu, 2 Apr 2020 04:38:36 -0300
Message-ID: <20200402073836.GA17269@alvherre.pgsql> (raw)
In-Reply-To: <20200402061421.GA112468@paquier.xyz>
On 2020-Apr-02, Michael Paquier wrote:
> Now, regarding patch 0002, note that you have a problem for this part:
> - tuple = SearchSysCache1(INDEXRELID, ObjectIdGetDatum(indexOid));
> - if (!HeapTupleIsValid(tuple)) /* probably can't happen */
> - {
> - relation_close(OldHeap, AccessExclusiveLock);
> - pgstat_progress_end_command();
> - return;
> - }
> - indexForm = (Form_pg_index) GETSTRUCT(tuple);
> - if (!indexForm->indisclustered)
> + if (!get_index_isclustered(indexOid))
> {
> - ReleaseSysCache(tuple);
> relation_close(OldHeap, AccessExclusiveLock);
> pgstat_progress_end_command();
> return;
> }
> - ReleaseSysCache(tuple);
>
> On an invalid tuple for pg_index, the new code would issue an error,
> while the old code would just return.
I don't think we need to worry about that problem, because we already
checked that the pg_class tuple for the index is there two lines above.
The pg_index tuple cannot have gone away on its own; and the index can't
be deleted either, because cluster_rel holds AEL on the table. There
isn't "probably" about the can't-happen condition, is there?
--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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To: pgsql-hackers@postgresql.org
Cc: alvherre@2ndquadrant.com, michael@paquier.xyz, pryzby@telsasoft.com, amitlangote09@gmail.com, tgl@sss.pgh.pa.us
Subject: Re: ALTER tbl rewrite loses CLUSTER ON index
In-Reply-To: <20200402073836.GA17269@alvherre.pgsql>
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