Tom Lane wrote:
[EMAIL PROTECTED] writes:
Reading 1/4, for a larger table, has a good chance of being faster than
reading 4/4 of the table. :-)
Really?
If you have to hit one tuple out of four, it's pretty much guaranteed
that you will need to fetch every heap page.
I think it's not uncommon to have data that is more clustered than expected.
In my case it shows up often in GIS data; where often a query
that only accesses 1/4 of the rows in the table really will
only access about 1/4 of the pages in the table -- for example
when analyzing Texas or the Southwest US.
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TIP 2: Don't 'kill -9' the postmaster
