Re: Implicit rule created for materialized views

Dave Page <dpage(at)pgadmin(dot)org> wrote:
> Kevin Grittner <kevin(dot)grittner(at)enterprisedb(dot)com> wrote:
>> Dave Page <dpage(at)pgadmin(dot)org> wrote:

>>> In playing with materialized views, I noticed that they still
>>> seem to have an _RETURN rule implicitly created like a regular
>>> view.

>> A materialized view is pretty much like a view, but with the
>> results materialized.
>
> Yeah, I get that, but what is confusing is that this now seems to
> be a special kind of relation where there is an ON SELECT DO
> INSTEAD rule which isn't actually executed on SELECTs from the
> view but at some arbitrary time in the future.

Perhaps this way of looking at it will allow it to make sense: It
generates values which will be returned by SELECT -- it just does
that in advance and caches them on disk for quicker return when
queried.

As a practical matter, a materialized view needs to store exactly
the same information about its query, in the same form, as a
regular view.  To add a new table to store this in a different
place, with references and such maintained in the same way, would
have multiplied the size of the patch with a lot of copy/pasted
code.  I'm pretty sure the result would have been something which
was harder to review and maintain.

--
Kevin Grittner
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