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Disallow LATERAL references to the target table of an UPDATE/DELETE.

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On second thought, commit 0c051c9008 was
over-hasty: rather than allowing this case, we ought to reject it for now.
That leaves the field clear for a future feature that allows the target
table to be re-specified in the FROM (or USING) clause, which will enable
left-joining the target table to something else.  We can then also allow
LATERAL references to such an explicitly re-specified target table.
But allowing them right now will create ambiguities or worse for such a
feature, and it isn't something we documented 9.3 as supporting.

While at it, add a convenience subroutine to avoid having several copies
of the ereport for disalllowed-LATERAL-reference cases.
This commit is contained in:
Tom Lane
2014-01-11 19:03:15 -05:00
parent 5bfcc9ec5e
commit 27ff4cfe76
5 changed files with 72 additions and 66 deletions
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48
src/test/regress/expected/join.out
View File

@@ -4057,17 +4057,7 @@ LINE 1: select 1 from tenk1 a, lateral (select max(a.unique1) from i...
^
-- 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;
x1 | x2
-------------+-------------
0 | 0
123456 | -123456
-123456 | 123456
2147483647 | -2147483647
-2147483647 | 2147483647
(5 rows)
-- error, can't do this without LATERAL:
-- error, can't do this:
update xx1 set x2 = f1 from (select * from int4_tbl where f1 = x1) ss;
ERROR: column "x1" does not exist
LINE 1: ... set x2 = f1 from (select * from int4_tbl where f1 = x1) ss;
@@ -4078,28 +4068,28 @@ ERROR: invalid reference to FROM-clause entry for table "xx1"
LINE 1: ...t x2 = f1 from (select * from int4_tbl where f1 = xx1.x1) ss...
^
HINT: There is an entry for table "xx1", but it cannot be referenced from this part of the query.
-- OK:
-- can't do it even with LATERAL:
update xx1 set x2 = f1 from lateral (select * from int4_tbl where f1 = x1) ss;
select * from xx1;
x1 | x2
-------------+-------------
0 | 0
123456 | 123456
-123456 | -123456
2147483647 | 2147483647
-2147483647 | -2147483647
(5 rows)
-- error:
ERROR: invalid reference to FROM-clause entry for table "xx1"
LINE 1: ...= f1 from lateral (select * from int4_tbl where f1 = x1) ss;
^
HINT: There is an entry for table "xx1", but it cannot be referenced from this part of the query.
-- we might in future allow something like this, but for now it's an error:
update xx1 set x2 = f1 from xx1, lateral (select * from int4_tbl where f1 = x1) ss;
ERROR: table name "xx1" specified more than once
-- also errors:
delete from xx1 using (select * from int4_tbl where f1 = x1) ss;
ERROR: column "x1" does not exist
LINE 1: ...te from xx1 using (select * from int4_tbl where f1 = x1) ss;
^
HINT: There is a column named "x1" in table "xx1", but it cannot be referenced from this part of the query.
-- OK:
delete from xx1 using (select * from int4_tbl where f1 = xx1.x1) ss;
ERROR: invalid reference to FROM-clause entry for table "xx1"
LINE 1: ...from xx1 using (select * from int4_tbl where f1 = xx1.x1) ss...
^
HINT: There is an entry for table "xx1", but it cannot be referenced from this part of the query.
delete from xx1 using lateral (select * from int4_tbl where f1 = x1) ss;
select * from xx1;
x1 | x2
----+----
(0 rows)
ERROR: invalid reference to FROM-clause entry for table "xx1"
LINE 1: ...xx1 using lateral (select * from int4_tbl where f1 = x1) ss;
^
HINT: There is an entry for table "xx1", but it cannot be referenced from this part of the query.

13
src/test/regress/sql/join.sql
View File

@@ -1137,17 +1137,16 @@ 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:
-- error, can't do this:
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:
-- can't do it even with LATERAL:
update xx1 set x2 = f1 from lateral (select * from int4_tbl where f1 = x1) ss;
select * from xx1;
-- we might in future allow something like this, but for now it's an error:
update xx1 set x2 = f1 from xx1, lateral (select * from int4_tbl where f1 = x1) ss;
-- error:
-- also errors:
delete from xx1 using (select * from int4_tbl where f1 = x1) ss;
-- OK:
delete from xx1 using (select * from int4_tbl where f1 = xx1.x1) ss;
delete from xx1 using lateral (select * from int4_tbl where f1 = x1) ss;
select * from xx1;