Date: Wed, 5 Dec 2012 19:08:07 -0800 (PST)
From: classical_89 <luongnx512@gmail.com>
To: pgsql-performance@postgresql.org
Message-ID: <1354763287777-5735406.post@n5.nabble.com>
Subject: Perform scan on Toast table
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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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