Message-ID: <43864a0e35504ffc6047dd90eaf648287ed75e65.camel@cybertec.at>
Subject: Re: pgstattuple_approx for toasted table
From: Laurenz Albe <laurenz.albe@cybertec.at>
To: Mariel Cherkassky <mariel.cherkassky@gmail.com>, PostgreSQL mailing
 lists <pgsql-performance@postgresql.org>
Date: Mon, 04 Mar 2019 06:21:39 +0100
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Organization: Cybertec
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Mariel Cherkassky wrote:
> I was testing pgstattuple and I realized that pgstattuple is working on toasted table but pgstattuple_approx is raising the next error msg : 
> 
> ERROR:  "pg_toast_18292" is not a table or materialized view
> 
> ahm, is that because the pgstattuple_approx uses visibility map ? Can someone explain ? tnx.

You are right; here is the code:

    /*
     * We support only ordinary relations and materialised views, because we
     * depend on the visibility map and free space map for our estimates about
     * unscanned pages.
     */
    if (!(rel->rd_rel->relkind == RELKIND_RELATION ||
          rel->rd_rel->relkind == RELKIND_MATVIEW))
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("\"%s\" is not a table or materialized view",
                        RelationGetRelationName(rel))));

Yours,
Laurenz Albe

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