From: | "Pavel Stehule" <pavel(dot)stehule(at)gmail(dot)com> |
---|---|
To: | "Pg Hackers" <pgsql-hackers(at)postgresql(dot)org> |
Subject: | 8.3 planner ignore index with text_pattern_ops for eq |
Date: | 2008-08-06 14:55:16 |
Message-ID: | 162867790808060755v75946dceo714cf7131eeddc54@mail.gmail.com |
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Lists: | pgsql-hackers |
Hello
there is some different behave between 8.3 and 8.1, 8.4 versions. 8.3
can't share index for like and equ op.
postgres=# select version();
version
----------------------------------------------------------------------------------------------------
PostgreSQL 8.3.0 on i686-pc-linux-gnu, compiled by GCC gcc (GCC)
4.1.2 20070925 (Red Hat 4.1.2-33)
(1 row)
postgres=# \i ~/Desktop/pagila-0.10.1/pagila-schema.sql
postgres=# \i ~/Desktop/pagila-0.10.1/pagila-data.sql
postgres=# CREATE index city_idx1 on city (city varchar_pattern_ops);
CREATE INDEX
postgres=# ANALYZE city
postgres-# ;
ANALYZE
postgres=# explain select * from city where city = 'Prague';
QUERY PLAN
------------------------------------------------------
Seq Scan on city (cost=0.00..11.50 rows=1 width=23)
Filter: ((city)::text = 'Prague'::text)
(2 rows)
postgres=# explain select * from city where city like 'Prague';
QUERY PLAN
-----------------------------------------------------------------------
Index Scan using city_idx1 on city (cost=0.00..8.27 rows=1 width=23)
Index Cond: ((city)::text ~=~ 'Prague'::text)
Filter: ((city)::text ~~ 'Prague'::text)
(3 rows)
postgres=# explain select * from city where city like 'Prague%';
QUERY PLAN
------------------------------------------------------------------------------------------
Index Scan using city_idx1 on city (cost=0.00..8.27 rows=1 width=23)
Index Cond: (((city)::text ~>=~ 'Prague'::text) AND ((city)::text
~<~ 'Praguf'::text))
Filter: ((city)::text ~~ 'Prague%'::text)
(3 rows)
8.4 works correct - is it possible backport?
Regards
Pavel Stehule
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Next Message | Tom Lane | 2008-08-06 15:03:29 | Re: 8.3 planner ignore index with text_pattern_ops for eq |
Previous Message | Tom Lane | 2008-08-06 14:42:52 | Re: Status of DISTINCT-by-hashing work |