| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Nicolas Barbier <nicolas(dot)barbier(at)gmail(dot)com> |
| Cc: | Kevin Grittner <kgrittn(at)ymail(dot)com>, Dean Rasheed <dean(dot)a(dot)rasheed(at)gmail(dot)com>, Greg Stark <stark(at)mit(dot)edu>, Ants Aasma <ants(at)cybertec(dot)at>, Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, Josh Berkus <josh(at)agliodbs(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Materialized views WIP patch |
| Date: | 2013-03-03 23:39:08 |
| Message-ID: | 17034.1362353948@sss.pgh.pa.us |
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Nicolas Barbier <nicolas(dot)barbier(at)gmail(dot)com> writes:
> 2013/3/3 Kevin Grittner <kgrittn(at)ymail(dot)com>:
>> Nicolas Barbier <nicolas(dot)barbier(at)gmail(dot)com> wrote:
>>> I think that automatically using materialized views even when the
>>> query doesnt mention them directly, is akin to automatically
>>> using indexes without having to mention them in the query.
>> Oh, I understand that concept perfectly well, I just wonder how
>> often it is useful in practice.
There's a much more fundamental reason why this will never happen, which
is that the query planner is not licensed to decide that you only want
an approximate and not an exact answer to your query.
If MVs were guaranteed always up-to-date, maybe we could think about
automatic use of them --- but that's a far different feature from what
Kevin has here.
regards, tom lane
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