Fix some issues with LATERAL(SELECT UNION ALL SELECT).

The LATERAL marking has to be propagated down to the UNION leaf queries
when we pull them up.  Also, fix the formerly stubbed-off
set_append_rel_pathlist().  It does already have enough smarts to cope with
making a parameterized Append path at need; it just has to not assume that
there *must* be an unparameterized path.

2 files changed, 35 insertions, 0 deletions

diff --git a/src/test/regress/expected/join.out b/src/test/regress/expected/join.out
index 5e17432198e..6503dd1d2f8 100644
--- a/src/test/regress/expected/join.out
+++ b/src/test/regress/expected/join.out
@@ -3109,6 +3109,32 @@ explain (costs off)
          ->  Function Scan on generate_series g
 (4 rows)
 
+-- lateral with UNION ALL subselect
+explain (costs off)
+  select * from generate_series(100,200) g,
+    lateral (select * from int8_tbl a where g = q1 union all
+             select * from int8_tbl b where g = q2) ss;
+                QUERY PLAN                
+------------------------------------------
+ Nested Loop
+   ->  Function Scan on generate_series g
+   ->  Append
+         ->  Seq Scan on int8_tbl a
+               Filter: (g.g = q1)
+         ->  Seq Scan on int8_tbl b
+               Filter: (g.g = q2)
+(7 rows)
+
+select * from generate_series(100,200) g,
+  lateral (select * from int8_tbl a where g = q1 union all
+           select * from int8_tbl b where g = q2) ss;
+  g  |        q1        |        q2        
+-----+------------------+------------------
+ 123 |              123 |              456
+ 123 |              123 | 4567890123456789
+ 123 | 4567890123456789 |              123
+(3 rows)
+
 -- test some error cases where LATERAL should have been used but wasn't
 select f1,g from int4_tbl a, generate_series(0, f1) g;
 ERROR:  column "f1" does not exist
diff --git a/src/test/regress/sql/join.sql b/src/test/regress/sql/join.sql
index 5de98dc0a72..40db5602dd4 100644
--- a/src/test/regress/sql/join.sql
+++ b/src/test/regress/sql/join.sql
@@ -876,6 +876,15 @@ explain (costs off)
 explain (costs off)
   select count(*) from tenk1 a cross join lateral generate_series(1,two) g;
 
+-- lateral with UNION ALL subselect
+explain (costs off)
+  select * from generate_series(100,200) g,
+    lateral (select * from int8_tbl a where g = q1 union all
+             select * from int8_tbl b where g = q2) ss;
+select * from generate_series(100,200) g,
+  lateral (select * from int8_tbl a where g = q1 union all
+           select * from int8_tbl b where g = q2) ss;
+
 -- test some error cases where LATERAL should have been used but wasn't
 select f1,g from int4_tbl a, generate_series(0, f1) g;
 select f1,g from int4_tbl a, generate_series(0, a.f1) g;