Further mucking with PlaceHolderVar-related restrictions on join order.

Commit 85e5e222b1 turns out not to have taken
care of all cases of the partially-evaluatable-PlaceHolderVar problem found
by Andreas Seltenreich's fuzz testing.  I had set it up to check for risky
PHVs only in the event that we were making a star-schema-based exception to
the param_source_rels join ordering heuristic.  However, it turns out that
the problem can occur even in joins that satisfy the param_source_rels
heuristic, in which case allow_star_schema_join() isn't consulted.
Refactor so that we check for risky PHVs whenever the proposed join has
any remaining parameterization.

Back-patch to 9.2, like the previous patch (except for the regression test
case, which only works back to 9.3 because it uses LATERAL).

Note that this discovery implies that problems of this sort could've
occurred in 9.2 and up even before the star-schema patch; though I've not
tried to prove that experimentally.

src/test/regress/expected/join.out

@@ -3000,6 +3000,26 @@ where t1.unique2 < 42 and t1.stringu1 > t2.stringu2;
       11 | WFAAAA   |       3 | LKIAAA
 (1 row)
 
+-- variant that isn't quite a star-schema case
+select ss1.d1 from
+  tenk1 as t1
+  inner join tenk1 as t2
+  on t1.tenthous = t2.ten
+  inner join
+    int8_tbl as i8
+    left join int4_tbl as i4
+      inner join (select 64::information_schema.cardinal_number as d1
+                  from tenk1 t3,
+                       lateral (select abs(t3.unique1) + random()) ss0(x)
+                  where t3.fivethous < 0) as ss1
+      on i4.f1 = ss1.d1
+    on i8.q1 = i4.f1
+  on t1.tenthous = ss1.d1
+where t1.unique1 < i4.f1;
+ d1 
+----
+(0 rows)
+
 --
 -- test extraction of restriction OR clauses from join OR clause
 -- (we used to only do this for indexable clauses)

src/test/regress/sql/join.sql

@@ -874,6 +874,24 @@ select t1.unique2, t1.stringu1, t2.unique1, t2.stringu2 from
   on (subq1.y1 = t2.unique1)
 where t1.unique2 < 42 and t1.stringu1 > t2.stringu2;
 
+-- variant that isn't quite a star-schema case
+
+select ss1.d1 from
+  tenk1 as t1
+  inner join tenk1 as t2
+  on t1.tenthous = t2.ten
+  inner join
+    int8_tbl as i8
+    left join int4_tbl as i4
+      inner join (select 64::information_schema.cardinal_number as d1
+                  from tenk1 t3,
+                       lateral (select abs(t3.unique1) + random()) ss0(x)
+                  where t3.fivethous < 0) as ss1
+      on i4.f1 = ss1.d1
+    on i8.q1 = i4.f1
+  on t1.tenthous = ss1.d1
+where t1.unique1 < i4.f1;
+
 --
 -- test extraction of restriction OR clauses from join OR clause
 -- (we used to only do this for indexable clauses)