Horton

Re: BUG #17803: Rule "ALSO INSERT ... SELECT ..." fails to substitute default values

Alexander Law <exclusion@gmail.com>

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From: Alexander Lakhin <exclusion@gmail.com>
To: Dean Rasheed <dean.a.rasheed@gmail.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, pgsql-bugs@lists.postgresql.org
Date: 2023-02-22T12:00:00Z
Lists: pgsql-bugs 
22.02.2023 12:07, Dean Rasheed wrote:
> On Wed, 22 Feb 2023 at 08:00, Alexander Lakhin <exclusion@gmail.com> wrote:
>> I have a minor question about the condition:
>> +                if (pt->commandType == CMD_INSERT ...
>> Is it possible to get another commandType there?
> Yes, there could also be ON INSERT DO ALSO UPDATE/DELETE rules. The
> new code is intended to apply only for DO ALSO INSERT .. SELECT rules
> (where the VALUES RTE in "pt" isn't in the usual place), but other
> types of command in the rule are also possible. As long as the
> top-level command is a multi-row INSERT ... VALUES (), (), ... it can
> reach this code block.

Thanks! I understand this place better now.
I mistakenly supposed that VALUES RTE can intervene with INSERT only.
But while exploring how they can affect other statements,
I've found one more interesting thing:
CREATE TABLE t (a int, b int DEFAULT -1);
CREATE VIEW v AS SELECT * FROM t;
CREATE RULE vr AS ON INSERT TO v DO ALSO INSERT INTO t SELECT NEW.b;
INSERT INTO v VALUES(10, -1), (20, DEFAULT);
SELECT * FROM v;

  a  | b
----+----
  10 | -1
  20 | -1
  -1 | -1
     | -1

It seems that a NEW field filled correctly if it is not DEFAULT,
but DEFAULT is lost somehow.

Best regards,
Alexander

Commits

  1. Fix mishandling of OLD/NEW references in subqueries in rule actions.

  2. Fix multi-row DEFAULT handling for INSERT ... SELECT rules.

  3. Fix DEFAULT-handling in multi-row VALUES lists for updatable views.