From: xu fei <autofei@yahoo.com>
To: pgsql-hackers@postgresql.org
Subject: full text search index scan query plan changed in 8.4.2?
Date: Sun, 28 Feb 2010 12:42:09 -0800 (PST)
Message-ID: <60218.64374.qm@web45406.mail.sp1.yahoo.com> (raw)
Hi, hackers:
I am testing the index used by full text search recently.
I have install 8.3.9 and 8.4.2 separately.
In 8.3.9, the query plan is like:
postgres=# explain SELECT s.name as source , t.name as target FROM element as s, element as t WHERE to_tsvector('testcfg',s.name) @@ to_tsquery('testcfg',replace(t.name,':','|')); QUERY PLAN ------------------------------------------------------------------------------------------------------------------------------------------------------------
Nested Loop (cost=0.01..259.92 rows=491 width=18)
-> Seq Scan on element t (cost=0.00..13.01 rows=701 width=9)
-> Index Scan using element_ftsidx_test on element s (cost=0.01..0.33 rows=1 width=9)
Index Cond: (to_tsvector('testcfg'::regconfig, (s.name)::text) @@ to_tsquery('testcfg'::regconfig, replace((t.name)::text, ':'::text, '|'::text)))
(4 rows)
I have index: "element_ftsidx_test" gin (to_tsvector('testcfg'::regconfig, name::text))
The same index and query in 8.4.2:
postgres=# explain SELECT s.name as source , t.name as target FROM element as s, element as t WHERE to_tsvector('testcfg',s.name) @@ to_tsquery('testcfg',replace(t.name,':','|')) ; QUERY PLAN ------------------------------------------------------------------------------------------------------------------------------------------------------------------
Nested Loop (cost=0.32..3123.51 rows=2457 width=18)
-> Seq Scan on element t (cost=0.00..13.01 rows=701 width=9)
-> Bitmap Heap Scan on element s (cost=0.32..4.36 rows=4 width=9) Recheck Cond: (to_tsvector('testcfg'::regconfig, (s.name)::text) @@ to_tsquery('testcfg'::regconfig, replace((t.name)::text, ':'::text, '|'::text)))
-> Bitmap Index Scan on element_ftsidx_test (cost=0.00..0.32 rows=4 width=0)
Index Cond: (to_tsvector('testcfg'::regconfig, (s.name)::text) @@ to_tsquery('testcfg'::regconfig, replace((t.name)::text, ':'::text, '|'::text)))
(6 rows)
Why the query plans are different and why? Thanks!
Xu Fei
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-performance@postgresql.org
Cc: autofei@yahoo.com, pgsql-hackers@postgresql.org
Subject: Re: full text search index scan query plan changed in 8.4.2?
In-Reply-To: <60218.64374.qm@web45406.mail.sp1.yahoo.com>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox