automatically refresh all materialized views?

On Fri, Feb 14, 2014 at 11:26 AM, Reece Hart <reece@harts.net> wrote:

Is there a way to automatically refresh all materialized views, preferably
in order of dependendency?

I should be able to chase pg_depends entries to create this ordering, right?

yeah -- you could do this with some gymnastics and some dynamic SQL.
If I were lazy (check), I would just encode the order in the name of
the view somehow.

merlin

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On Fri, Feb 14, 2014 at 10:15 AM, Merlin Moncure <mmoncure@gmail.com> wrote:

yeah -- you could do this with some gymnastics and some dynamic SQL.
If I were lazy (check), I would just encode the order in the name of
the view somehow.

Thanks. That's exactly what I do already. Apparently, I'm even lazier than
you!

In case anyone out there is looking for a convention, here's one that I
find useful: _v for views intended for interactive queries, _dv (defining
views) for views that are too slow to use interactively, and _mv for the
materialized _dv views.

On Fri, Feb 14, 2014 at 7:26 PM, Reece Hart <reece@harts.net> wrote:

I should be able to chase pg_depends entries to create this ordering, right?

Not always, there may be circular dependencies between them.

Regards,
Marti

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Marti Raudsepp <marti@juffo.org> wrote:

Reece Hart <reece@harts.net> wrote:

I should be able to chase pg_depends entries to create this
ordering, right?

Not always, there may be circular dependencies between them.

I haven't been able to think of a way to create circular references
among a set of materialized views, short of committing violence
against the system catalog tables directly. What have I missed?

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Kevin Grittner
EDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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Kevin Grittner <kgrittn@ymail.com> writes:

Marti Raudsepp <marti@juffo.org> wrote:

Not always, there may be circular dependencies between them.

I haven't been able to think of a way to create circular references
among a set of materialized views, short of committing violence
against the system catalog tables directly. What have I missed?

It'd be pretty trivial if we had CREATE OR REPLACE MATERIALIZED VIEW.

Which I assume is not there only for lack of round tuits, and not
because you deliberately intend that it will never be implemented.

regards, tom lane

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On Tue, Mar 11, 2014 at 9:17 PM, Kevin Grittner <kgrittn@ymail.com> wrote:

I haven't been able to think of a way to create circular references
among a set of materialized views, short of committing violence
against the system catalog tables directly. What have I missed?

Not directly, but you can create circles with matviews selecting from
ordinary views:

create view v_a as select 1 i;
create materialized view m_a as select * from v_a;
create view v_b as select * from m_a;
create materialized view m_b as select * from v_b;
create or replace view v_a as select * from m_b; -- Cha-ching!

You probably won't hit them if you don't recurse into views in
pg_depends, but then you might miss some necessary dependencies.

I didn't really give this much thought though. Such a setup might not
be refresh'able after a restore because you run into a recursive
"materialized view "x" has not been populated". (Maybe it is possible
if the recursive reference occurs in a subquery that isn't scanned?
dunno)

Now that I tried it, pg_dump has this to say:

pg_dump: [sorter] WARNING: could not resolve dependency loop among these items:
pg_dump: [sorter] REFRESH MATERIALIZED VIEW m_a (ID 1971 OID 18834835)
pg_dump: [sorter] WARNING: could not resolve dependency loop among these items:
pg_dump: [sorter] REFRESH MATERIALIZED VIEW m_b (ID 1972 OID 18834843)
pg_dump: [sorter] WARNING: could not resolve dependency loop among these items:
pg_dump: [sorter] REFRESH MATERIALIZED VIEW m_a (ID 1971 OID 18834835)
pg_dump: [sorter] REFRESH MATERIALIZED VIEW m_b (ID 1972 OID 18834843)

Regards,
Marti

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