Fix ruleutils.c for domain-over-array cases, too.

Further investigation shows that ruleutils isn't quite up to speed either
for cases where we have a domain-over-array: it needs to be prepared to
look past a CoerceToDomain at the top level of field and element
assignments, else it decompiles them incorrectly.  Potentially this would
result in failure to dump/reload a rule, if it looked like the one in the
new test case.  (I also added a test for EXPLAIN; that output isn't broken,
but clearly we need more test coverage here.)

Like commit b1cb32fb6, this bug is reachable in cases we already support,
so back-patch all the way.

2 files changed, 45 insertions, 8 deletions

diff --git a/src/test/regress/expected/domain.out b/src/test/regress/expected/domain.out
index 0385757ad7a..d2f9730d66e 100644
--- a/src/test/regress/expected/domain.out
+++ b/src/test/regress/expected/domain.out
@@ -266,20 +266,48 @@ insert into dcomptable (d1[1].r, d1[1].i) values(100, 99);  -- fail
 ERROR:  value for domain dcomptypea violates check constraint "c1"
 update dcomptable set d1[1].r = d1[1].r + 1 where d1[1].i > 0;  -- fail
 ERROR:  value for domain dcomptypea violates check constraint "c1"
-update dcomptable set d1[1].r = d1[1].r - 1 where d1[1].i > 0;
+update dcomptable set d1[1].r = d1[1].r - 1, d1[1].i = d1[1].i + 1
+  where d1[1].i > 0;
 select * from dcomptable;
          d1         
 --------------------
  {"(11,)","(,)"}
  {"(99,)"}
- {"(1,2)","(,)"}
- {"(3,4)","(6,5)"}
- {"(7,8)","(10,9)"}
- {"(9,10)","(,)"}
- {"(0,2)"}
- {"(98,100)"}
+ {"(1,3)","(,)"}
+ {"(3,5)","(6,5)"}
+ {"(7,9)","(10,9)"}
+ {"(9,11)","(,)"}
+ {"(0,3)"}
+ {"(98,101)"}
 (8 rows)
 
+explain (verbose, costs off)
+  update dcomptable set d1[1].r = d1[1].r - 1, d1[1].i = d1[1].i + 1
+    where d1[1].i > 0;
+                                                 QUERY PLAN                                                 
+------------------------------------------------------------------------------------------------------------
+ Update on public.dcomptable
+   ->  Seq Scan on public.dcomptable
+         Output: (d1[1].r := (d1[1].r - 1::double precision))[1].i := (d1[1].i + 1::double precision), ctid
+         Filter: (dcomptable.d1[1].i > 0::double precision)
+(4 rows)
+
+create rule silly as on delete to dcomptable do instead
+  update dcomptable set d1[1].r = d1[1].r - 1, d1[1].i = d1[1].i + 1
+    where d1[1].i > 0;
+\d+ dcomptable
+                        Table "public.dcomptable"
+ Column |    Type    | Modifiers | Storage  | Stats target | Description 
+--------+------------+-----------+----------+--------------+-------------
+ d1     | dcomptypea |           | extended |              | 
+Indexes:
+    "dcomptable_d1_key" UNIQUE CONSTRAINT, btree (d1)
+Rules:
+    silly AS
+    ON DELETE TO dcomptable DO INSTEAD  UPDATE dcomptable SET d1[1].r = dcomptable.d1[1].r - 1::double precision, d1[1].i = dcomptable.d1[1].i + 1::double precision
+  WHERE dcomptable.d1[1].i > 0::double precision
+Has OIDs: no
+
 drop table dcomptable;
 drop type comptype cascade;
 NOTICE:  drop cascades to type dcomptypea
diff --git a/src/test/regress/sql/domain.sql b/src/test/regress/sql/domain.sql
index fae95c6861b..c149efc347c 100644
--- a/src/test/regress/sql/domain.sql
+++ b/src/test/regress/sql/domain.sql
@@ -150,9 +150,18 @@ insert into dcomptable (d1[1].r) values(99);
 insert into dcomptable (d1[1].r, d1[1].i) values(99, 100);
 insert into dcomptable (d1[1].r, d1[1].i) values(100, 99);  -- fail
 update dcomptable set d1[1].r = d1[1].r + 1 where d1[1].i > 0;  -- fail
-update dcomptable set d1[1].r = d1[1].r - 1 where d1[1].i > 0;
+update dcomptable set d1[1].r = d1[1].r - 1, d1[1].i = d1[1].i + 1
+  where d1[1].i > 0;
 select * from dcomptable;
 
+explain (verbose, costs off)
+  update dcomptable set d1[1].r = d1[1].r - 1, d1[1].i = d1[1].i + 1
+    where d1[1].i > 0;
+create rule silly as on delete to dcomptable do instead
+  update dcomptable set d1[1].r = d1[1].r - 1, d1[1].i = d1[1].i + 1
+    where d1[1].i > 0;
+\d+ dcomptable
+
 drop table dcomptable;
 drop type comptype cascade;