From: classical_89 <luongnx512@gmail.com>
To: pgsql-performance@postgresql.org
Subject: Perform scan on Toast table
Date: Wed, 5 Dec 2012 19:08:07 -0800 (PST)
Message-ID: <1354763287777-5735406.post@n5.nabble.com> (raw)
List-Unsubscribe: <mailto:majordomo@postgresql.org?body=unsub%20pgsql-performance>
Hi everyone ,I have a question. I have a table with large data (i was used
bytea datatype and insert a binary content to table ) so that Postgres help
me get a TOAST table to storage out-of-line values .
Assume that my table is " tbl_test " and toast table oid is 16816
When i peform EXPLAIN ANALYZE select query on tbl_test ( EXPLAIN ANALYZE
SELECT * FROM tbl_test).It show that sequential scan was performed on
tbl_test ,but when i check pg_toast table with this query :
SELECT
relid,
schemaname,
relname,
seq_scan,
seq_tup_read,
idx_scan,
FROM pg_stat_all_tables
WHERE relid IN ( SELECT oid
FROM pg_class
WHERE relkind = 't' ) AND relid = 16816
I saw that seq_tup_read = 0 and the seq_scan is always is 1 .idx_scan is
increase arcording to the number of query on tbl_test
I was wordering : Do have a sequential scan perform on tbl_test and other
index scan will be peforming on TOAST after this sequential scan ?
Can you explain this dump question to me ,please ?
P/S : sorry for my bad English .Thanks ! :)
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To: pgsql-performance@postgresql.org
Cc: luongnx512@gmail.com
Subject: Re: Perform scan on Toast table
In-Reply-To: <1354763287777-5735406.post@n5.nabble.com>
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