Re: get_relation_stats_hook()

From: Simon Riggs <simon(at)2ndquadrant(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Alvaro Herrera <alvherre(at)commandprompt(dot)com>
Cc: pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: get_relation_stats_hook()
Date: 2008-06-26 16:02:50
Views: Raw Message | Whole Thread | Download mbox | Resend email
Lists: pgsql-hackers pgsql-patches

On Thu, 2008-06-26 at 11:18 -0400, Tom Lane wrote:
> Simon Riggs <simon(at)2ndquadrant(dot)com> writes:
> > Currently we have a plugin capability for get_relation_info_hook(), but
> > no corresponding capability for statistics info.
> > So, all calls to SearchSysCache would be replaced with a call to
> > get_relation_info_hook(), if present.
> Surely you didn't mean ALL calls. Please be more specific about what
> you're proposing.

The statistics relation STATRELATT is accessed in a few places in the
planner. Since it is in the syscache it is accessed directly from there.
I would like to add hooks so that stats data can come from somewhere
else other than the syscache for tables, just as we can already do with
get_relation_stats_hook(). These new changes would complete the existing
feature to ensure it is fully usabled in the way originally intended.

In selfunc.c: There are 3 calls to SearchSysCache(STATRELATT,...).

In lsyscache.c: There is 1 call to SearchSysCache(STATRELATT...) in
get_attavgwidth() and 2 calls to SysCacheGetAttr(STATRELATT...) in

Calls to SearchSysCache(STATRELATT...) would be replaced by a call to an
external module, if present, with a function pointer to
get_relation_stats_hook(). This returns a tuple with stats info about
that relation.

Calls to SysCacheGetAttr(STATRELATT...) would be replaced by a call to
an external module, if present with a function pointer to
get_attribute_stats_hook(). This returns a stats slot.

The call in ANALYZE would not be touched.

Simon Riggs
PostgreSQL Training, Services and Support

In response to


Browse pgsql-hackers by date

  From Date Subject
Next Message David E. Wheeler 2008-06-26 16:02:56 Re: Latest on CITEXT 2.0
Previous Message Pavel Stehule 2008-06-26 15:40:13 proposal: to_ascii(bytea)

Browse pgsql-patches by date

  From Date Subject
Next Message Josh Berkus 2008-06-26 16:29:44 Re: [0/4] Proposal of SE-PostgreSQL patches
Previous Message KaiGai Kohei 2008-06-26 15:32:32 Re: [0/4] Proposal of SE-PostgreSQL patches