Improve regression test case to avoid depending on system catalog stats.

In commit 95f4e59c32866716 I added a regression test case that examined
the plan of a query on system catalogs.  That isn't a terribly great idea
because the catalogs tend to change from version to version, or even
within a version if someone makes an unrelated regression-test change that
populates the catalogs a bit differently.  Usually I try to make planner
test cases rely on test tables that have not changed since Berkeley days,
but I got sloppy in this case because the submitted crasher example queried
the catalogs and I didn't spend enough time on rewriting it.  But it was a
problem waiting to happen, as I was rudely reminded when I tried to port
that patch into Salesforce's Postgres variant :-(.  So spend a little more
effort and rewrite the query to not use any system catalogs.  I verified
that this version still provokes the Assert if 95f4e59c32866716's code fix
is reverted.

I also removed the EXPLAIN output from the test, as it turns out that the
assertion occurs while considering a plan that isn't the one ultimately
selected anyway; so there's no value in risking any cross-platform
variation in that printout.

Back-patch to 9.2, like the previous patch.

src/test/regress/expected/join.out

@@ -2220,51 +2220,21 @@ order by 1, 2;
 
 --
 -- regression test: check a case where join_clause_is_movable_into() gives
--- an imprecise result
+-- an imprecise result, causing an assertion failure
 --
-analyze pg_enum;
-explain (costs off)
-select anname, outname, enumtypid
+select count(*)
 from
-  (select pa.proname as anname, coalesce(po.proname, typname) as outname
-   from pg_type t
-     left join pg_proc po on po.oid = t.typoutput
-     join pg_proc pa on pa.oid = t.typanalyze) ss,
-  pg_enum,
-  pg_type t2
-where anname = enumlabel and outname = t2.typname and enumtypid = t2.oid;
-                              QUERY PLAN                               
------------------------------------------------------------------------
- Nested Loop
-   Join Filter: (pg_enum.enumtypid = t2.oid)
-   ->  Nested Loop Left Join
-         ->  Hash Join
-               Hash Cond: ((t.typanalyze)::oid = pa.oid)
-               ->  Seq Scan on pg_type t
-               ->  Hash
-                     ->  Hash Join
-                           Hash Cond: (pa.proname = pg_enum.enumlabel)
-                           ->  Seq Scan on pg_proc pa
-                           ->  Hash
-                                 ->  Seq Scan on pg_enum
-         ->  Index Scan using pg_proc_oid_index on pg_proc po
-               Index Cond: (oid = (t.typoutput)::oid)
-   ->  Index Scan using pg_type_typname_nsp_index on pg_type t2
-         Index Cond: (typname = COALESCE(po.proname, t.typname))
-(16 rows)
-
-select anname, outname, enumtypid
-from
-  (select pa.proname as anname, coalesce(po.proname, typname) as outname
-   from pg_type t
-     left join pg_proc po on po.oid = t.typoutput
-     join pg_proc pa on pa.oid = t.typanalyze) ss,
-  pg_enum,
-  pg_type t2
-where anname = enumlabel and outname = t2.typname and enumtypid = t2.oid;
- anname | outname | enumtypid 
---------+---------+-----------
-(0 rows)
+  (select t3.tenthous as x1, coalesce(t1.stringu1, t2.stringu1) as x2
+   from tenk1 t1
+   left join tenk1 t2 on t1.unique1 = t2.unique1
+   join tenk1 t3 on t1.unique2 = t3.unique2) ss,
+  tenk1 t4,
+  tenk1 t5
+where t4.thousand = t5.unique1 and ss.x1 = t4.tenthous and ss.x2 = t5.stringu1;
+ count 
+-------
+  1000
+(1 row)
 
 --
 -- Clean up

src/test/regress/sql/join.sql

@@ -379,29 +379,17 @@ order by 1, 2;
 
 --
 -- regression test: check a case where join_clause_is_movable_into() gives
--- an imprecise result
+-- an imprecise result, causing an assertion failure
 --
-analyze pg_enum;
-explain (costs off)
-select anname, outname, enumtypid
+select count(*)
 from
-  (select pa.proname as anname, coalesce(po.proname, typname) as outname
-   from pg_type t
-     left join pg_proc po on po.oid = t.typoutput
-     join pg_proc pa on pa.oid = t.typanalyze) ss,
-  pg_enum,
-  pg_type t2
-where anname = enumlabel and outname = t2.typname and enumtypid = t2.oid;
-
-select anname, outname, enumtypid
-from
-  (select pa.proname as anname, coalesce(po.proname, typname) as outname
-   from pg_type t
-     left join pg_proc po on po.oid = t.typoutput
-     join pg_proc pa on pa.oid = t.typanalyze) ss,
-  pg_enum,
-  pg_type t2
-where anname = enumlabel and outname = t2.typname and enumtypid = t2.oid;
+  (select t3.tenthous as x1, coalesce(t1.stringu1, t2.stringu1) as x2
+   from tenk1 t1
+   left join tenk1 t2 on t1.unique1 = t2.unique1
+   join tenk1 t3 on t1.unique2 = t3.unique2) ss,
+  tenk1 t4,
+  tenk1 t5
+where t4.thousand = t5.unique1 and ss.x1 = t4.tenthous and ss.x2 = t5.stringu1;
 
 
 --