From: Tom Lane <tgl@sss.pgh.pa.us>
To: Lars Aksel Opsahl <Lars.Opsahl@nibio.no>
Cc: Vijaykumar Jain <vijaykumarjain.github@gmail.com>
Cc: Pgsql Performance <pgsql-performance@lists.postgresql.org>
Subject: Re: slow "select count(*) from information_schema.tables;" in some cases
Date: Mon, 07 Feb 2022 14:02:50 -0500
Message-ID: <1016661.1644260570@sss.pgh.pa.us> (raw)
In-Reply-To: <AM7P189MB10285F4025EA9299DD9C3DEA9D2C9@AM7P189MB1028.EURP189.PROD.OUTLOOK.COM>
References: <AM7P189MB1028F684ADED9D89722C85C19D2C9@AM7P189MB1028.EURP189.PROD.OUTLOOK.COM>
<CAM+6J941cquhkv=8VJz19VqCTTscRzyL8Uj7DZ11VBjErwh4dQ@mail.gmail.com>
<AM7P189MB10285F4025EA9299DD9C3DEA9D2C9@AM7P189MB1028.EURP189.PROD.OUTLOOK.COM>
Lars Aksel Opsahl <Lars.Opsahl@nibio.no> writes:
>> SELECT relname, pg_size_pretty(pg_relation_size(C.oid)) FROM pg_class C LEFT JOIN pg_namespace N ON (N.oid = C.relnamespace) WHERE nspname = 'pg_catalog' ORDER BY 2 DESC LIMIT 20; can you show the output of this query
"ORDER BY 2" is giving you a textual sort of the sizes, which is entirely
unhelpful. Try
SELECT relname, pg_size_pretty(pg_relation_size(C.oid)) FROM pg_class C LEFT JOIN pg_namespace N ON (N.oid = C.relnamespace) WHERE nspname = 'pg_catalog' ORDER BY pg_relation_size(C.oid) DESC LIMIT 20;
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, Lars.Opsahl@nibio.no, vijaykumarjain.github@gmail.com, pgsql-performance@lists.postgresql.org
Subject: Re: slow "select count(*) from information_schema.tables;" in some cases
In-Reply-To: <1016661.1644260570@sss.pgh.pa.us>
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