Horton

Re: unsupportable composite type partition keys

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Amit Langote <amitlangote09@gmail.com>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2019-12-22T21:51:15Z
Lists: pgsql-hackers

Attachments

I wrote:
> Now as far as point 1 goes, I think it's not really that awful to use
> CheckAttributeType() with a dummy attribute name.  The attached
> incomplete patch uses "partition key" which causes it to emit errors
> like
> regression=# create table fool (a int, b int) partition by list ((row(a, b))); 
> ERROR:  column "partition key" has pseudo-type record
> I don't think that that's unacceptable.  But if we wanted to improve it,
> we could imagine adding another flag, say CHKATYPE_IS_PARTITION_KEY,
> that doesn't affect CheckAttributeType's semantics, just the wording of
> the error messages it throws.

Here's a fleshed-out patch that does it like that.

While poking at this, I also started to wonder why CheckAttributeType
wasn't recursing into ranges, since those are our other kind of
container type.  And the answer is that it must, because we allow
creation of ranges over composite types:

regression=# create table foo (f1 int, f2 int);
CREATE TABLE
regression=# create type foorange as range (subtype = foo);
CREATE TYPE
regression=# alter table foo add column r foorange;
ALTER TABLE

Simple things still work on table foo, but surely this is exactly
what CheckAttributeType is supposed to be preventing.  With the
second attached patch you get

regression=# alter table foo add column r foorange;
ERROR:  composite type foo cannot be made a member of itself

The second patch needs to go back all the way, the first one
only as far as we have partitions.

			regards, tom lane

Commits

  1. Fix CheckAttributeType's handling of collations for ranges.

  2. Improve comments in utils/rel.h.

  3. Allow whole-row Vars to be used in partitioning expressions.

  4. Remove equalPartitionDescs().

  5. Load relcache entries' partitioning data on-demand, not immediately.

  6. Disallow partition key expressions that return pseudo-types.

  7. Prevent a rowtype from being included in itself via a range.