Re: Why we don't want hints

Scott Marlowe <scott.marlowe@gmail.com>

From: Scott Marlowe <scott.marlowe@gmail.com>

To: Josh Berkus <josh@agliodbs.com>

Cc: pgsql-performance@postgresql.org

Date: 2011-02-14T07:01:37Z

Lists: pgsql-hackers, pgsql-performance

On Sun, Feb 13, 2011 at 10:49 PM, Josh Berkus <josh@agliodbs.com> wrote:
>
>> I fail to see how 1 through 3 can tell the planner the correlation
>> between two fields in two separate tables.
>
> CREATE CORRELATION_ESTIMATE ( table1.colA ) = ( table2.colB ) IS 0.3
>
> ... and then it fixes the correlation for *every* query in the database, not
> just that one.  And is easy to fix if the correlation changes.

I like that.  Even better, could we setup some kind of simple command
to tell analyze to collect stats for the two columns together?