From: Tom Lane <tgl@sss.pgh.pa.us>
To: Alvaro Herrera <alvherre@2ndquadrant.com>
cc: Peter Geoghegan <pg@bowt.ie>,
        PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Subject: Re: Fixing findDependentObjects()'s dependency on scan order
 (regressions in DROP diagnostic messages)
In-reply-to: <19220.1547767251@sss.pgh.pa.us>
References: <201901172247.uqvtve6ekpvh@alvherre.pgsql>
 <19220.1547767251@sss.pgh.pa.us>
Comments: In-reply-to Tom Lane <tgl@sss.pgh.pa.us>
	message dated "Thu, 17 Jan 2019 18:20:51 -0500"
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Date: Thu, 17 Jan 2019 18:57:36 -0500
Message-ID: <20599.1547769456@sss.pgh.pa.us>
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I wrote:
> Also, I am suspicious that this implementation fails on point 3
> anyway ... If nothing else, it looks like ALTER OBJECT DEPENDS ON
> EXTENSION can be used to attach a random dependency to just
> about anything.

Yup:

regression=3D# drop table if exists idxpart cascade;
DROP TABLE
regression=3D# create table idxpart (a int) partition by range (a);
CREATE TABLE
regression=3D# create index on idxpart (a);
CREATE INDEX
regression=3D# create table idxpart1 partition of idxpart for values from =
(0) to (10);
CREATE TABLE
regression=3D# drop index idxpart1_a_idx;      -- no way
ERROR:  cannot drop index idxpart1_a_idx because index idxpart_a_idx requi=
res it
HINT:  You can drop index idxpart_a_idx instead.
regression=3D# \d idxpart1
              Table "public.idxpart1"
 Column |  Type   | Collation | Nullable | Default =

--------+---------+-----------+----------+---------
 a      | integer |           |          | =

Partition of: idxpart FOR VALUES FROM (0) TO (10)
Indexes:
    "idxpart1_a_idx" btree (a)
regression=3D# create extension cube;
CREATE EXTENSION
regression=3D# alter index idxpart1_a_idx depends on extension cube;
ALTER INDEX
regression=3D# drop extension cube;
DROP EXTENSION
regression=3D# \d idxpart1
              Table "public.idxpart1"
 Column |  Type   | Collation | Nullable | Default =

--------+---------+-----------+----------+---------
 a      | integer |           |          | =

Partition of: idxpart FOR VALUES FROM (0) TO (10)


			regards, tom lane