From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
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To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | pgsql-hackers(at)postgreSQL(dot)org |
Subject: | Re: Parallel appendrel scans? |
Date: | 2016-07-04 03:02:14 |
Message-ID: | 83755E07-C435-493F-9F93-F727604D66A1@gmail.com |
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Lists: | pgsql-hackers |
On Jul 3, 2016, at 6:58 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> It looks to me like set_append_rel_pathlist builds a partial path for
> an appendrel only if there exist partial paths for all members of the
> appendrel. I don't understand this restriction. Why could you not
> build it from a regular path for each appendrel child? You'd have
> to farm out entire childrels to workers, which might be larger chunks
> of work than one could wish, but it seems better than failing to
> parallelize at all.
Absolutely. The problem is merely that we need some executor support that has not been written yet. See discussions of Parallel Append in the archives.
...Robert
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