| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | "Christopher Kings-Lynne" <chris(dot)kingslynne(at)gmail(dot)com> |
| Cc: | "Jim C(dot) Nasby" <jnasby(at)pervasive(dot)com>, "Hannu Krosing" <hannu(at)skype(dot)net>, "Peter Eisentraut" <peter_e(at)gmx(dot)net>, pgsql-hackers(at)postgresql(dot)org, Perez <arturo(at)ethicist(dot)net> |
| Subject: | Re: An Idea for planner hints |
| Date: | 2006-08-16 03:14:17 |
| Message-ID: | 28658.1155698057@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
"Christopher Kings-Lynne" <chris(dot)kingslynne(at)gmail(dot)com> writes:
> see. Collecting the statistics thereafter isn't that hard, but there
> needs to be a way to not collect an exponential volume of statistics on
> all column combinations.
> You could collect them on all FK relationships - is that enough?
As somebody pointed out upthread, collecting these stats on FK
relationships is actually not very interesting: you already know
that the referenced side of the relationship is a unique column,
and so the selectivity stats of the referencing side are enough.
regards, tom lane
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