Fix LATERAL references to target table of UPDATE/DELETE.

I failed to think much about UPDATE/DELETE when implementing LATERAL :-(.
The implemented behavior ended up being that subqueries in the FROM or
USING clause (respectively) could access the update/delete target table as
though it were a lateral reference; which seems fine if they said LATERAL,
but certainly ought to draw an error if they didn't.  Fix it so you get a
suitable error when you omit LATERAL.  Per report from Emre Hasegeli.

1 files changed, 18 insertions, 0 deletions

diff --git a/src/test/regress/sql/join.sql b/src/test/regress/sql/join.sql
index 2168c55722..e2bf915be0 100644
--- a/src/test/regress/sql/join.sql
+++ b/src/test/regress/sql/join.sql
@@ -1147,3 +1147,21 @@ select * from
   int8_tbl x cross join (int4_tbl x cross join lateral (select x.f1) ss);
 -- LATERAL can be used to put an aggregate into the FROM clause of its query
 select 1 from tenk1 a, lateral (select max(a.unique1) from int4_tbl b) ss;
+
+-- check behavior of LATERAL in UPDATE/DELETE
+
+create temp table xx1 as select f1 as x1, -f1 as x2 from int4_tbl;
+select * from xx1;
+
+-- error, can't do this without LATERAL:
+update xx1 set x2 = f1 from (select * from int4_tbl where f1 = x1) ss;
+update xx1 set x2 = f1 from (select * from int4_tbl where f1 = xx1.x1) ss;
+-- OK:
+update xx1 set x2 = f1 from lateral (select * from int4_tbl where f1 = x1) ss;
+select * from xx1;
+
+-- error:
+delete from xx1 using (select * from int4_tbl where f1 = x1) ss;
+-- OK:
+delete from xx1 using lateral (select * from int4_tbl where f1 = x1) ss;
+select * from xx1;