> The computed cost of using the index was a factor of 10 higher which I
presume is why the query planner wasn't
> using the index, but it ran in half the time
Have you tried playing with the random_page_cost parameter? The default is
4. Try:
set random_page_cost = 1;
in psql to alter it for th
"David Witham" <[EMAIL PROTECTED]> writes:
> Does this make it a "wide" table?
Nope. A rough estimate is that your rows will be about 160 bytes wide,
which means you can fit about 50 per 8K page. So a query that needs to
select 8% of the table will *on average* need to hit about 4 rows per
page.
e.
I hope this makes sense. Does it help any?
Thanks,
David
-Original Message-
From: Tom Lane [mailto:[EMAIL PROTECTED]
Sent: Wednesday, 18 February 2004 16:10
To: David Witham
Cc: [EMAIL PROTECTED]
Subject: Re: [SQL] Indexes and statistics
"David Witham" <[EMAIL PROTECTED]&g
"David Witham" <[EMAIL PROTECTED]> writes:
> One of the customers is quite large (8.3% of the records):
Hmm. Unless your rows are quite wide, a random sampling of 8.3% of the
table would be expected to visit every page of the table, probably
several times. So the planner's cost estimates do not
Hi all,
This is a further post from last week. I've got a table of phone call detail records.
buns=# select count(*) from cdr;
count
-
2800653
(1 row)
One of the customers is quite large (8.3% of the records):
buns=# select count(*) from cdr where cust_id =
