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Date: Fri, 4 Jul 2008 05:36:40 -0700 (PDT)
From: Jessica Richard <rjessil@yahoo.com>
Subject: Re: slow delete...
To: Charles Duffy <charles.duffy@gmail.com>
Cc: pgsql-admin@postgresql.org
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thanks a lot. I imagine this will help me a lot. I will give it a try!!!

One more question: in the explain output, what is that "Bitmap Heap Scan on test"?, is it a bad thing (a table scan)? I would love to see the index scan instead of this Heap scan... what does "Heap Scan" actually do here?

 Bitmap Heap Scan on test  (cost=2110.49..10491.57 rows=79766 width=6)
   Recheck Cond: ((cola)::text = 'abc'::text)
   ->  Bitmap Index Scan on test_cola_idx  (cost=0.00..2090.55 rows=79766 width=0)
         Index Cond: ((cola)::text = 'abc'::text)
(4 rows)

Thanks again,
Jessica



----- Original Message ----
From: Charles Duffy <charles.duffy@gmail.com>
To: Jessica Richard <rjessil@yahoo.com>
Cc: pgsql-admin@postgresql.org
Sent: Friday, July 4, 2008 3:17:43 AM
Subject: Re: [ADMIN] slow delete...

> by the way, there is a foreign key on another table that references the
> primary key col0 on table test.
>

Try putting an index on the FK column in the other table. Analyse the
table. Test by starting a transaction then
issuing: explain analyze delete from test where cola = 'abc'. Should be faster.


Charles Duffy

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<html><head><style type="text/css"><!-- DIV {margin:0px;} --></style></head><body><div style="font-family:times new roman, new york, times, serif;font-size:12pt"><div>thanks a lot. I imagine this will help me a lot. I will give it a try!!!<br><br>One more question: in the explain output, what is that "Bitmap Heap Scan on test"?, is it a bad thing (a table scan)? I would love to see the index scan instead of this Heap scan... what does "Heap Scan" actually do here?<br><br>&nbsp;Bitmap Heap Scan on test&nbsp; (cost=2110.49..10491.57 rows=79766 width=6)<br>&nbsp;&nbsp; Recheck Cond: ((cola)::text = 'abc'::text)<br>&nbsp;&nbsp; -&gt;&nbsp; Bitmap Index Scan on test_cola_idx&nbsp; (cost=0.00..2090.55 rows=79766 width=0)<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Index Cond: ((cola)::text = 'abc'::text)<br>(4 rows)<br><br>Thanks again,<br>Jessica<br></div><div style="font-family: times new roman,new york,times,serif; font-size: 12pt;"><br><div
 style="font-family: arial,helvetica,sans-serif; font-size: 13px;">----- Original Message ----<br>From: Charles Duffy &lt;charles.duffy@gmail.com&gt;<br>To: Jessica Richard &lt;rjessil@yahoo.com&gt;<br>Cc: pgsql-admin@postgresql.org<br>Sent: Friday, July 4, 2008 3:17:43 AM<br>Subject: Re: [ADMIN] slow delete...<br><br>
&gt; by the way, there is a foreign key on another table that references the<br>&gt; primary key col0 on table test.<br>&gt;<br><br>Try putting an index on the FK column in the other table. Analyse the<br>table. Test by starting a transaction then<br>issuing: explain analyze delete from test where cola = 'abc'. Should be faster.<br><br><br>Charles Duffy<br><br>-- <br>Sent via pgsql-admin mailing list (<a ymailto="mailto:pgsql-admin@postgresql.org" href="mailto:pgsql-admin@postgresql.org">pgsql-admin@postgresql.org</a>)<br>To make changes to your subscription:<br><a href="http://www.postgresql.org/mailpref/pgsql-admin" target="_blank">http://www.postgresql.org/mailpref/pgsql-admin</a><br></div></div></div><br>



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