Message-Id: <7.0.1.0.2.20070115145412.0545bb68@brownpapertickets.com>
Date: Mon, 15 Jan 2007 14:55:28 -0800
To: pgsql-sql@postgresql.org
From: William Scott Jordan <wsjordan@brownpapertickets.com>
Subject: Re: Resolved - Referencing tables are grinding UPDATE to
In-Reply-To: <7.0.1.0.2.20070115124931.06433838@pandimensional.org>
References: <7.0.1.0.2.20070115124931.06433838@pandimensional.org>
Mime-Version: 1.0
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Yeah, I forgot about the RULE on that table.  Ignore my previous email.

-Scott

At 01:26 PM 1/15/2007, you wrote:
>Hey all!
>
>I'm having some trouble with a simple update on a table that only 
>has about 250,000 rows in it.  The table itself looks something like:
>
>CREATE TABLE price_details (
>price_detail_id int PRIMARY KEY,
>private bool
>) ;
>
>There is one table that references price_details, but isn't affected 
>by the "private" column, and one table that references this second 
>table.  They look something like:
>
>CREATE TABLE prices (
>p_id int PRIMARY KEY,
>price_detail_id int NOT NULL REFERENCES price_details ON DELETE CASCADE,
>max_sales int
>) ;
>
>CREATE INDEX prices_price_detail_id  ON prices (price_detail_id) ;
>
>CREATE TABLE sales (
>sales_id int PRIMARY KEY,
>p_id int NOT NULL REFERENCES prices ON DELETE CASCADE,
>sales int
>) ;
>
>CREATE INDEX sales_p_id ON sales (p_id) ;
>
>I'm trying to do a simple update to the "private" column in the 
>price_details table, which I expected to take a few seconds at 
>most.  After 10 minutes, I gave up and ran explain, with this as the result:
>
>
>EXPLAIN UPDATE price_details SET private = 't' WHERE private = 'f' ;
>----------------------------------------------------------------------------------------
>  Nested Loop  (cost=2663.45..363527947.70 rows=118759098 width=50)
>    Join Filter: (subplan)
>    ->  Seq Scan on sales  (cost=0.00..3685.27 rows=54627 width=42)
>    ->  Materialize  (cost=2663.45..2706.93 rows=4348 width=12)
>          ->  Seq Scan on price_details  (cost=0.00..2663.45 
> rows=4348 width=12)
>                Filter: (private  = false)
>    SubPlan
>      ->  Index Scan using prices_price_detail_id on 
> prices  (cost=0.00..3.01 rows=1 width=4)
>            Index Cond: (price_detail_id = $0)
>
>  Seq Scan on price_details  (cost=0.00..2663.45 rows=4348 width=508)
>    Filter: (private = false)
>(12 rows)
>----------------------------------------------------------------------------------------
>
>So it looks to me like the postgres is checking this table against 
>the table that references it, and the table that reference that 
>table, making what should be a very easy transaction into something 
>unusable.  Is there any way to avoid this without losing proper referencing?
>
>Any suggestions would be appreciated.
>
>-Scott
>
>
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