Re: index scan cost
От
Tom Lane
Тема
Re: index scan cost
Дата
Msg-id
9919.1216355851@sss.pgh.pa.us
Ответ на
index scan cost (Jeff Frost)
Список
Дерево обсуждения
index scan cost Jeff Frost <jeff@frostconsultingllc.com>
Re: index scan cost "Dennis Brakhane" <brakhane@googlemail.com>
Re: index scan cost Jeff Frost <jeff@frostconsultingllc.com>
Re: index scan cost Tom Lane <tgl@sss.pgh.pa.us>
Mailing list hacked by spammer? Craig James <craig_james@emolecules.com>
Re: Mailing list hacked by spammer? Steve Atkins <steve@blighty.com>
Re: Mailing list hacked by spammer? Alvaro Herrera <alvherre@commandprompt.com>
Re: index scan cost Jeff Frost <jeff@frostconsultingllc.com>
Jeff Frost writes: > I have two postgresql servers. One runs 8.3.1, the other 8.3.3. On the 8.3.1 > machine, the index scans are being planned extremely low cost: > Index Scan using ix_email_entity_thread on email_entity (cost=0.00..4.59 > rows=1 width=1031) (actual time=0.095..0.120 rows=4 loops=1) > Index Cond: (email_thread = 375629157) > Index Scan using ix_email_entity_thread on email_entity (cost=0.00..2218.61 > rows=1151 width=931) (actual time=0.094..0.111 rows=4 loops=1) > Index Cond: (email_thread = 375629157) This isn't a "cost" problem, this is a "stats" problem. Why does the second server think 1151 rows will be returned? Try comparing the pg_stats entries for the email_thread column on both servers ... seems like they must be significantly different. regards, tom lane
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