From: Tom Lane <tgl@sss.pgh.pa.us>
To: CG <cgg007@yahoo.com>
Cc: pgsql-sql@postgresql.org
Subject: Re: Nested loops are killing throughput
Date: Tue, 19 Sep 2006 11:03:07 -0400
Message-ID: <4769.1158678187@sss.pgh.pa.us> (raw)
In-Reply-To: <20060919144628.32833.qmail@web37903.mail.mud.yahoo.com>
References: <20060919144628.32833.qmail@web37903.mail.mud.yahoo.com>
CG <cgg007@yahoo.com> writes:
> -> Nested Loop (cost=0.00..744.28 rows=1 width=16) (actual time=31.227..6980.765 rows=5436 loops=1)
> -> Nested Loop (cost=0.00..135.29 rows=101 width=16) (actual time=25.514..273.660 rows=5436 loops=1)
> ...
> -> Index Scan using packet_status_puuid_pkey on packet_status dps (cost=0.00..6.02 rows=1 width=16) (actual time=1.226..1.228 rows=1 loops=5436)
> Index Cond: (dps.packet_uuid = "outer".packet_uuid)
> Filter: ((status & 2) = 0)
One problem you've got is that the planner has no stats about the
selectivity of that status condition. My advice would be to forget the
cute bitmask and store one or more plain boolean columns. Easier to
write queries against and way more tractable statistically.
regards, tom lane
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To: pgsql-sql@postgresql.org
Cc: tgl@sss.pgh.pa.us, cgg007@yahoo.com
Subject: Re: Nested loops are killing throughput
In-Reply-To: <4769.1158678187@sss.pgh.pa.us>
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