Re: WIP: Avoid creation of the free space map for small tables

From: John Naylor <john(dot)naylor(at)2ndquadrant(dot)com>
To: Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
Cc: Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>, Mithun Cy <mithun(dot)cy(at)enterprisedb(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: WIP: Avoid creation of the free space map for small tables
Date: 2019-01-31 13:53:44
Message-ID: CACPNZCtFfFKK4=BFaKG=rbWEXNG3W=LY6nJ7p=B7usjN3UE2XA@mail.gmail.com
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On Thu, Jan 31, 2019 at 1:52 PM John Naylor <john(dot)naylor(at)2ndquadrant(dot)com> wrote:
>
> On Thu, Jan 31, 2019 at 1:43 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> > > I have an idea -- instead of adding a bunch of records and hoping that
> > > the relation size and free space is consistent across platforms, how
> > > about we revert to the original test input, and add a BRIN index? That
> > > should have a FSM even with one record.
> > >
> >
> > Why would BRIN index allow having FSM for heap relation?
>
> Oops, I forgot this file is for testing heaps only. That said, we
> could possibly put most of the FSM tests such as
>
> SELECT * FROM fsm_page_contents(get_raw_page('test_rel_forks', 'fsm', 0));
>
> into brin.sql since we know a non-empty BRIN index will have a FSM.

As in the attached. Applies on top of v20. First to revert to HEAD,
second to move FSM tests to brin.sql. This is a much less invasive and
more readable patch, in addition to being hopefully more portable.

> And in page.sql we could just have a test that the table has no FSM.

This is not possible, since we don't know the relfilenode for the
error text, and it's not important. Better to have everything in
brin.sql.

--
John Naylor https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

Attachment Content-Type Size
revert-pageinspect.patch text/x-patch 6.4 KB
move-pageinspect-fsm-tests-to-brin.patch text/x-patch 5.8 KB

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