pg_restore -t should match views, matviews, and foreign tables

On 3/31/15 11:01 PM, Craig Ringer wrote:

Following on from this -bugs post:

/messages/by-id/CAMsr+YGJ50TvTVK4Dbp66gAjeOC0KaP6KXFEHAOM+neQmHvoQA@mail.gmail.com

this patch adds support for views, foreign tables, and materialised
views to the pg_restore -t flag.

I think this is a good change. Any concerns?

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Peter Eisentraut <peter_e@gmx.net> writes:

On 3/31/15 11:01 PM, Craig Ringer wrote:

this patch adds support for views, foreign tables, and materialised
views to the pg_restore -t flag.

I think this is a good change. Any concerns?

Are we happy with pg_dump/pg_restore not distinguishing these objects
by type? It seems rather analogous to letting ALTER TABLE work on views
etc. Personally I'm fine with this, but certainly some people have
complained about that approach so far as ALTER is concerned. (But the
implication would be that we'd need four distinct switches, which is
not an outcome I favor.)

Also, I think you missed "MATERIALIZED VIEW DATA".

Also, shouldn't there be a documentation update?

regards, tom lane

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On Tue, Apr 7, 2015 at 1:33 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:

Peter Eisentraut <peter_e@gmx.net> writes:

On 3/31/15 11:01 PM, Craig Ringer wrote:

this patch adds support for views, foreign tables, and materialised
views to the pg_restore -t flag.

I think this is a good change. Any concerns?

Are we happy with pg_dump/pg_restore not distinguishing these objects
by type? It seems rather analogous to letting ALTER TABLE work on views
etc. Personally I'm fine with this, but certainly some people have
complained about that approach so far as ALTER is concerned. (But the
implication would be that we'd need four distinct switches, which is
not an outcome I favor.)

​The pg_dump documentation for the equivalent "-t" switch states:

​"Dump only tables (or views or sequences or foreign tables) matching table"

Does pg_dump need to be updated to address materialized views here?

Does pg_restore need to be updated to address sequences here?

ISTM that the two should mirror each other.

David J.

On 8 April 2015 at 04:33, Tom Lane <tgl@sss.pgh.pa.us> wrote:

Peter Eisentraut <peter_e@gmx.net> writes:

On 3/31/15 11:01 PM, Craig Ringer wrote:

this patch adds support for views, foreign tables, and materialised
views to the pg_restore -t flag.

I think this is a good change. Any concerns?

Are we happy with pg_dump/pg_restore not distinguishing these objects
by type? It seems rather analogous to letting ALTER TABLE work on views
etc. Personally I'm fine with this, but certainly some people have
complained about that approach so far as ALTER is concerned. (But the
implication would be that we'd need four distinct switches, which is
not an outcome I favor.)

My reasoning was that these are all relations that, as far as SELECT et al
are concerned, can be interchangeable.

I guess this is more like the ALTER TABLE case though - if you "pg_restore
-t" a view, you don't get the data from any table(s) it depends on. So
substituting a table for a view won't be transparent to the user anyway.

I mostly just don't see the point of requiring multiple flags for things
that are all in the same namespace. It'll mean new flags each time we add
some new object type, more logic in apps that invoke pg_restore, etc, and
for what seems like no meaningful gain. We'll just land up with "No table
'viewblah' matched, did you mean -V 'viewblah'? "

Also, I think you missed "MATERIALIZED VIEW DATA".

Thanks, amended.

Also, shouldn't there be a documentation update?

Yes. Again, amended.

I've also added mention of materialized views to the pg_dump docs for
--table, which omitted them.

(It's rather unfortunate that pg_restore's -t is completely different to
pg_dump's -t . Fixing that would involve implementing wildcard search
support in pg_restore and would break backward compatibility, though).

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Craig Ringer http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services

On 8 April 2015 at 05:05, David G. Johnston <david.g.johnston@gmail.com>
wrote:

On Tue, Apr 7, 2015 at 1:33 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:

Peter Eisentraut <peter_e@gmx.net> writes:

On 3/31/15 11:01 PM, Craig Ringer wrote:

this patch adds support for views, foreign tables, and materialised
views to the pg_restore -t flag.

I think this is a good change. Any concerns?

Are we happy with pg_dump/pg_restore not distinguishing these objects
by type? It seems rather analogous to letting ALTER TABLE work on views
etc. Personally I'm fine with this, but certainly some people have
complained about that approach so far as ALTER is concerned. (But the
implication would be that we'd need four distinct switches, which is
not an outcome I favor.)

​The pg_dump documentation for the equivalent "-t" switch states:

​"Dump only tables (or views or sequences or foreign tables) matching
table"

Does pg_dump need to be updated to address materialized views here?

The pg_dump code handles materialized views, the docs weren't updated. I
added mention of them in the next rev of the patch to pg_restore.

Does pg_restore need to be updated to address sequences here?

I'd be against that if pg_dump didn't already behave the same way. Given
that, yes, I think so.

ISTM that the two should mirror each other.

Ideally, yes, but the differences go much deeper than this.

to get the equivalent of:

pg_restore -n myschema -t sometable

in pg_dump you need:

pg_dump -t "\"myschema\".\"sometable\""

pg_dump -n myschema -t sometable is **not** equivalent. In fact, the -n is
ignored, and -t will match using the search_path.

so they're never really going to be the same, just similar enough to catch
people out most of the time.

I think you're right that sequences should be included by pg_restore since
they are by pg_dump, though. So v3 patch attached.

--
Craig Ringer http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services

Hi

I am sending a review of this trivial patch.

1.This patch enables the possibility to restore only selected view, mat.
view, foreign table or sequence. Currently the option -t works with tables
only. All other relation like objects are quietly ignored. With this patch,
the check on type is enhanced to allow other types described by pg_class
system table. The implementation is trivial:

 +            strcmp(te->desc, "TABLE DATA") == 0 ||
+            strcmp(te->desc, "VIEW") == 0 ||
+            strcmp(te->desc, "FOREIGN TABLE") == 0 ||
+            strcmp(te->desc, "MATERIALIZED VIEW") == 0 ||
+            strcmp(te->desc, "MATERIALIZED VIEW DATA") == 0 ||
+            strcmp(te->desc, "SEQUENCE") == 0)

2. There was not any objections against this patch.
3. There was not any problem with patching and compilation.
4. This feature is good enough documented.

There is opened question, if the related line should be changed? The
current text is not 100% accurate, but it is short, and well readable and
understandable.

-S, --superuser=NAME superuser user name to use for disabling
triggers
-t, --table=NAME restore named table
-T, --trigger=NAME restore named trigger

5. All tests passed

6. There are no tests. But pg_dump related sw has not any tests yet.

I don't see any issues - this patch is really trivial without risks. It is
working already on pg_dump side, so the fix on pg_restore side is natural.

Regards

Pavel

2015-04-01 5:01 GMT+02:00 Craig Ringer <craig@2ndquadrant.com>:

Craig Ringer <craig@2ndquadrant.com> writes:

I think you're right that sequences should be included by pg_restore since
they are by pg_dump, though. So v3 patch attached.

You forgot "SEQUENCE SET" :-(. I fixed that and adjusted the docs a bit
more and committed.

regards, tom lane

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