From: Rob Schall <rschall@callone.net>
To: pgsql-performance@postgresql.org
Subject: Identical Queries
Date: Thu, 01 Mar 2007 09:43:25 -0600
Message-ID: <45E6F49D.3010707@callone.net> (raw)
Question for anyone...
I tried posting to the bugs, and they said this is a better question for here.
I have to queries. One runs in about 2 seconds. The other takes upwards
of 2 minutes. I have a temp table that is created with 2 columns. This
table is joined with the larger database of call detail records.
However, these 2 queries are handled very differently.
The queries:
First----
calldetail=> EXPLAIN SELECT current.* FROM current JOIN anitmp ON
current.destnum=anitmp.ani AND istf=true;
QUERY PLAN
--------------------------------------------------------------------------------------
Nested Loop (cost=0.00..2026113.09 rows=500908 width=108)
-> Seq Scan on anitmp (cost=0.00..33.62 rows=945 width=8)
Filter: (istf = true)
-> Index Scan using i_destnum on current (cost=0.00..2137.36
rows=531 width=108)
Index Cond: (current.destnum = "outer".ani)
(5 rows)
Second----
calldetail=> EXPLAIN SELECT current.* FROM current JOIN anitmp ON
current.orignum=anitmp.ani AND istf=false;
QUERY PLAN
---------------------------------------------------------------------------
Hash Join (cost=35.99..3402035.53 rows=5381529 width=108)
Hash Cond: ("outer".orignum = "inner".ani)
-> Seq Scan on current (cost=0.00..907191.05 rows=10170805 width=108)
-> Hash (cost=33.62..33.62 rows=945 width=8)
-> Seq Scan on anitmp (cost=0.00..33.62 rows=945 width=8)
Filter: (istf = false)
(6 rows)
The tables:
Table "public.current"
Column | Type | Modifiers
----------+-----------------------------+-----------
datetime | timestamp without time zone |
orignum | bigint |
destnum | bigint |
billto | bigint |
cost | numeric(6,4) |
duration | numeric(8,1) |
origcity | character(12) |
destcity | character(12) |
file | character varying(30) |
linenum | integer |
carrier | character(1) |
Indexes:
"i_destnum" btree (destnum)
"i_orignum" btree (orignum)
Table "public.anitmp"
Column | Type | Modifiers
--------+---------+-----------
ani | bigint |
istf | boolean |
I was also asked to post the EXPLAIN ANALYZE for both:
calldetail=> EXPLAIN ANALYZE SELECT current.* FROM anitmp JOIN current ON istf=false AND current.orignum=anitmp.ani;
QUERY PLAN
-----------------------------------------------------------------------------------------------------------------------------------
Hash Join (cost=35.99..3427123.39 rows=5421215 width=108) (actual time=1994.164..157443.544 rows=157 loops=1)
Hash Cond: ("outer".orignum = "inner".ani)
-> Seq Scan on current (cost=0.00..913881.09 rows=10245809 width=108) (actual time=710.986..137963.320 rows=10893541 loops=1)
-> Hash (cost=33.62..33.62 rows=945 width=8) (actual time=10.948..10.948 rows=0 loops=1)
-> Seq Scan on anitmp (cost=0.00..33.62 rows=945 width=8) (actual time=10.934..10.939 rows=2 loops=1)
Filter: (istf = false)
Total runtime: 157443.900 ms
(7 rows)
calldetail=> EXPLAIN ANALYZE SELECT current.* FROM current JOIN anitmp ON current.destnum=anitmp.ani AND istf=true;
QUERY PLAN
-------------------------------------------------------------------------------------------------------------------------------------
Nested Loop (cost=0.00..2037526.69 rows=504602 width=108) (actual time=88.752..1050.295 rows=1445 loops=1)
-> Seq Scan on anitmp (cost=0.00..33.62 rows=945 width=8) (actual time=8.189..8.202 rows=2 loops=1)
Filter: (istf = true)
-> Index Scan using i_destnum on current (cost=0.00..2149.40 rows=534 width=108) (actual time=62.365..517.454 rows=722 loops=2)
Index Cond: (current.destnum = "outer".ani)
Total runtime: 1052.862 ms
(6 rows)
Anyone have any ideas for me? I have indexes on each of the necessary
columns.
Rob
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To: pgsql-performance@postgresql.org
Cc: rschall@callone.net
Subject: Re: Identical Queries
In-Reply-To: <45E6F49D.3010707@callone.net>
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