From: Rural Hunter <ruralhunter@gmail.com>
To: pgsql-performance@postgresql.org
Subject: Very slow planning performance on partition table
Date: Wed, 23 Jul 2014 21:21:00 +0800
Message-ID: <53CFB6BC.4050606@gmail.com> (raw)
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Hi,
I have a table partitioned with about 60 children tables. Now I found
the planning time of simple query with partition key are very slow.
# explain analyze select count(*) as cnt from article where pid=88 and
hash_code='2ca3ff8b17b163f0212c2ba01b80a064';
QUERY PLAN
-----------------------------------------------------------------------------------------------------------------------------------------------------
Aggregate (cost=16.55..16.56 rows=1 width=0) (actual
time=0.259..0.259 rows=1 loops=1)
-> Append (cost=0.00..16.55 rows=2 width=0) (actual
time=0.248..0.250 rows=1 loops=1)
-> Seq Scan on article (cost=0.00..0.00 rows=1 width=0)
(actual time=0.002..0.002 rows=0 loops=1)
Filter: ((pid = 88) AND (hash_code =
'2ca3ff8b17b163f0212c2ba01b80a064'::bpchar))
-> Index Scan using article_88_hash_idx on article_88
article (cost=0.00..16.55 rows=1 width=0) (actual time=0.246..0.248
rows=1 loops=1)
Index Cond: (hash_code =
'2ca3ff8b17b163f0212c2ba01b80a064'::bpchar)
Filter: (pid = 88)
Total runtime: 3.816 ms
(8 rows)
Time: 30999.986 ms
You can see the timing output that the actual run time of the 'explain
analyze' is 30 seconds while the select sql itself takes only 3 ms. My
partition key is on article.pid and the constraint is simple like this:
CONSTRAINT article_88_pid_check CHECK (pid = 88). What's wrong and how
can I improve the planning performance?
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To: pgsql-performance@postgresql.org
Cc: ruralhunter@gmail.com
Subject: Re: Very slow planning performance on partition table
In-Reply-To: <53CFB6BC.4050606@gmail.com>
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