From: | Mat Arye <mat(at)timescale(dot)com> |
---|---|
To: | pgsql-hackers(at)postgresql(dot)org |
Subject: | Additional Statistics Hooks |
Date: | 2018-03-12 17:03:57 |
Message-ID: | CADsUR0D5yq0LJfg5jyWEAq5SE+1E-3rqF09fk7z6ykx+EM4iUw@mail.gmail.com |
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Lists: | pgsql-hackers |
Hi All,
I have a question about statistics hooks. I am trying to teach the planner
that when grouping by something like date_trunc('1 day', time) will produce
a lot less rows than the number of distinct time values. I want to do that
in an extension. The problem is that I don't see a way to make
the get_relation_stats_hook work well fo that since by the time it's called
you only see the `time` var and not the full expression. None of the other
hooks seem appropriate either. So 2 questions:
1) Would people be opposed to adding a code hook somewhere at the start of
`examine_variable` (selfuncs.c) to allow creating statistics on complete
expressions? I can submit a patch if this seems reasonable.
2) Do patches that add code hooks (and are probably under 10 lines) need to
go through the entire commitfest process. I guess what I am really asking
is if PG12 would be the first version such a patch could appear in or is
PG11 still a possibility? Just wondering what the policy on such stuff is.
Thanks,
Mat
TimescaleDB
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