Re: pg_relation_size performance issue

I'm not sure why you are adding toast to table size, since pg_relation_size already does that.

http://www.postgresql.org/docs/9.3/interactive/functions-admin.html

This query might work better and faster for you.

SELECT n.nspname as schema,
             c.relname as table,
             a.rolname as owner,
             c.relfilenode as filename,
             c.reltuples::integer,
             pg_size_pretty(pg_relation_size( quote_ident( n.nspname ) || '.' || quote_ident( c.relname ) )) as size,
             pg_size_pretty(pg_total_relation_size( quote_ident( n.nspname ) || '.' || quote_ident( c.relname ) )) as total_size,
             pg_relation_size( quote_ident( n.nspname ) || '.' || quote_ident( c.relname ) ) as size_bytes,
             pg_total_relation_size( quote_ident( n.nspname ) || '.' || quote_ident( c.relname ) ) as total_size_bytes,
            CASE WHEN c.reltablespace = 0
                        THEN 'pg_default'
                        ELSE (SELECT t.spcname
                                     FROM pg_tablespace t WHERE (t.oid = c.reltablespace) )
                         END as tablespace
   FROM pg_class c
      JOIN pg_namespace n ON (n.oid = c.relnamespace)
     JOIN pg_authid a ON ( a.oid = c.relowner )
WHERE c.relname = 'sensor'
      AND n.nspname = 'devtest';

On Thu, Jun 4, 2015 at 9:50 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:

Hans Guijt <hg@terma.com> writes:
> I have a Postgres 9.3.7 database, freshly created on Ubuntu 14 LTS 64 bit, and at this time almost completely empty. I'm attempting to find the size of a table, using the following code:
> SELECT
>   pg_relation_size (stat.relid),
>   CASE WHEN cl.reltoastrelid = 0 THEN
>   0
>   ELSE
>   pg_relation_size (cl.reltoastrelid) + COALESCE ((
>   SELECT SUM (pg_relation_size (indexrelid)) FROM pg_index WHERE indrelid=cl.reltoastrelid
>   ), 0)::int8
> END,
> COALESCE ((SELECT SUM (pg_relation_size (indexrelid)) FROM pg_index WHERE indrelid=stat.relid), 0)::int8
> FROM pg_stat_all_tables stat
> JOIN pg_class cl ON cl.oid=stat.relid
> JOIN pg_namespace ns ON cl.relnamespace=ns.oid
> WHERE UPPER (cl.relname) = UPPER ('sensor')
>    AND UPPER (ns.nspname) = UPPER ('devtest')

Getting rid of the useless join to pg_stat_all_tables would probably help;
there's a lot of computation in that view.

                        regards, tom lane


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