Fix ALTER TABLE code to update domain constraints when needed.

It's possible for dropping a column, or altering its type, to require
changes in domain CHECK constraint expressions; but the code was
previously only expecting to find dependent table CHECK constraints.
Make the necessary adjustments.

This is a fairly old oversight, but it's a lot easier to encounter
the problem in the context of domains over composite types than it
was before.  Given the lack of field complaints, I'm not going to
bother with a back-patch, though I'd be willing to reconsider that
decision if someone does complain.

Patch by me, reviewed by Michael Paquier

Discussion: https://postgr.es/m/30656.1509128130@sss.pgh.pa.us

2 files changed, 45 insertions, 0 deletions

diff --git a/src/test/regress/expected/domain.out b/src/test/regress/expected/domain.out
index f7f3948d431..f4eebb75cf2 100644
--- a/src/test/regress/expected/domain.out
+++ b/src/test/regress/expected/domain.out
@@ -286,6 +286,31 @@ Rules:
 drop table dcomptable;
 drop type comptype cascade;
 NOTICE:  drop cascades to type dcomptype
+-- check altering and dropping columns used by domain constraints
+create type comptype as (r float8, i float8);
+create domain dcomptype as comptype;
+alter domain dcomptype add constraint c1 check ((value).r > 0);
+comment on constraint c1 on domain dcomptype is 'random commentary';
+select row(0,1)::dcomptype;  -- fail
+ERROR:  value for domain dcomptype violates check constraint "c1"
+alter type comptype alter attribute r type varchar;  -- fail
+ERROR:  operator does not exist: character varying > double precision
+HINT:  No operator matches the given name and argument types. You might need to add explicit type casts.
+alter type comptype alter attribute r type bigint;
+alter type comptype drop attribute r;  -- fail
+ERROR:  cannot drop composite type comptype column r because other objects depend on it
+DETAIL:  constraint c1 depends on composite type comptype column r
+HINT:  Use DROP ... CASCADE to drop the dependent objects too.
+alter type comptype drop attribute i;
+select conname, obj_description(oid, 'pg_constraint') from pg_constraint
+  where contypid = 'dcomptype'::regtype;  -- check comment is still there
+ conname |  obj_description  
+---------+-------------------
+ c1      | random commentary
+(1 row)
+
+drop type comptype cascade;
+NOTICE:  drop cascades to type dcomptype
 -- Test domains over arrays of composite
 create type comptype as (r float8, i float8);
 create domain dcomptypea as comptype[];
diff --git a/src/test/regress/sql/domain.sql b/src/test/regress/sql/domain.sql
index 5201f008a1c..68da27de22b 100644
--- a/src/test/regress/sql/domain.sql
+++ b/src/test/regress/sql/domain.sql
@@ -159,6 +159,26 @@ drop table dcomptable;
 drop type comptype cascade;
 
 
+-- check altering and dropping columns used by domain constraints
+create type comptype as (r float8, i float8);
+create domain dcomptype as comptype;
+alter domain dcomptype add constraint c1 check ((value).r > 0);
+comment on constraint c1 on domain dcomptype is 'random commentary';
+
+select row(0,1)::dcomptype;  -- fail
+
+alter type comptype alter attribute r type varchar;  -- fail
+alter type comptype alter attribute r type bigint;
+
+alter type comptype drop attribute r;  -- fail
+alter type comptype drop attribute i;
+
+select conname, obj_description(oid, 'pg_constraint') from pg_constraint
+  where contypid = 'dcomptype'::regtype;  -- check comment is still there
+
+drop type comptype cascade;
+
+
 -- Test domains over arrays of composite
 
 create type comptype as (r float8, i float8);