Date: Sat, 9 Feb 2019 12:56:13 -0300
From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Amit Langote <amitlangote09@gmail.com>, 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)
Message-ID: <20190209155613.GA2091@alvherre.pgsql>
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On 2019-Feb-09, Tom Lane wrote:

> Amit Langote <amitlangote09@gmail.com> writes:
> > On Sat, Feb 9, 2019 at 9:41 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> >> +1.  The best solution would presumably be to go through the normal
> >> object deletion mechanism; though possibly there's a reason that
> >> won't work given you're already inside some other DDL.
> 
> > Maybe:
> > - CatalogTupleDelete(trigrel, &trigtup->t_self);
> > + RemoveTriggerById(trgform->oid)?
> 
> No, that's still the back end of the deletion machinery, and in particular
> it would fail to clean pg_depend entries for the trigger.  Going in by the
> front door would use performDeletion().  (See deleteOneObject() to get
> an idea of what's being possibly missed out here.)

This patch I think does the right thing.

-- 
Álvaro Herrera                https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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commit 7031ce2b1f79a2e03b29ac896f0a008b0621d654
Author:     Alvaro Herrera <alvherre@alvh.no-ip.org>
AuthorDate: Sat Feb 9 12:31:25 2019 -0300
CommitDate: Sat Feb 9 12:53:00 2019 -0300

    fix trigger drop

diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 910e5deaa3f..923866b7e11 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -8024,17 +8024,21 @@ CloneFkReferencing(Relation pg_constraint, Relation parentRel,
 			while ((trigtup = systable_getnext(scan)) != NULL)
 			{
 				Form_pg_trigger	trgform = (Form_pg_trigger) GETSTRUCT(trigtup);
+				ObjectAddress	trigger;
 
 				if (trgform->tgconstrrelid != fk->conrelid)
 					continue;
 				if (trgform->tgrelid != fk->confrelid)
 					continue;
 
-				deleteDependencyRecordsForClass(TriggerRelationId,
-												HeapTupleGetOid(trigtup),
-												ConstraintRelationId,
-												DEPENDENCY_INTERNAL);
-				CatalogTupleDelete(trigrel, &trigtup->t_self);
+				deleteDependencyRecordsFor(TriggerRelationId,
+										   HeapTupleGetOid(trigtup),
+										   false);
+				/* make dependency deletion visible to performDeletion */
+				CommandCounterIncrement();
+				ObjectAddressSet(trigger, TriggerRelationId,
+								 HeapTupleGetOid(trigtup));
+				performDeletion(&trigger, DROP_RESTRICT, 0);
 			}
 
 			systable_endscan(scan);

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