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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.
This commit is contained in:
Tom Lane 2014-01-07 15:25:16 -05:00
parent f68220df92
commit 0c051c9008
5 changed files with 95 additions and 0 deletions
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21
src/backend/parser/analyze.c
View File

@ -342,6 +342,7 @@ static Query *
transformDeleteStmt(ParseState *pstate, DeleteStmt *stmt)
{
Query *qry = makeNode(Query);
ParseNamespaceItem *nsitem;
Node *qual;
qry->commandType = CMD_DELETE;
@ -360,8 +361,15 @@ transformDeleteStmt(ParseState *pstate, DeleteStmt *stmt)
true,
ACL_DELETE);
/* grab the namespace item made by setTargetTable */
nsitem = (ParseNamespaceItem *) llast(pstate->p_namespace);
/* there's no DISTINCT in DELETE */
qry->distinctClause = NIL;
/* subqueries in USING can see the result relation only via LATERAL */
nsitem->p_lateral_only = true;
/*
* The USING clause is non-standard SQL syntax, and is equivalent in
* functionality to the FROM list that can be specified for UPDATE. The
@ -370,6 +378,9 @@ transformDeleteStmt(ParseState *pstate, DeleteStmt *stmt)
*/
transformFromClause(pstate, stmt->usingClause);
/* remaining clauses can see the result relation normally */
nsitem->p_lateral_only = false;
qual = transformWhereClause(pstate, stmt->whereClause,
EXPR_KIND_WHERE, "WHERE");
@ -1889,6 +1900,7 @@ static Query *
transformUpdateStmt(ParseState *pstate, UpdateStmt *stmt)
{
Query *qry = makeNode(Query);
ParseNamespaceItem *nsitem;
RangeTblEntry *target_rte;
Node *qual;
ListCell *origTargetList;
@ -1910,12 +1922,21 @@ transformUpdateStmt(ParseState *pstate, UpdateStmt *stmt)
true,
ACL_UPDATE);
/* grab the namespace item made by setTargetTable */
nsitem = (ParseNamespaceItem *) llast(pstate->p_namespace);
/* subqueries in FROM can see the result relation only via LATERAL */
nsitem->p_lateral_only = true;
/*
* the FROM clause is non-standard SQL syntax. We used to be able to do
* this with REPLACE in POSTQUEL so we keep the feature.
*/
transformFromClause(pstate, stmt->fromClause);
/* remaining clauses can see the result relation normally */
nsitem->p_lateral_only = false;
qry->targetList = transformTargetList(pstate, stmt->targetList,
EXPR_KIND_UPDATE_SOURCE);

4
src/backend/parser/parse_clause.c
View File

@ -204,6 +204,10 @@ setTargetTable(ParseState *pstate, RangeVar *relation,
/*
* If UPDATE/DELETE, add table to joinlist and namespace.
*
* Note: some callers know that they can find the new ParseNamespaceItem
* at the end of the pstate->p_namespace list. This is a bit ugly but not
* worth complicating this function's signature for.
*/
if (alsoSource)
addRTEtoQuery(pstate, rte, true, true, true);

4
src/backend/parser/parse_relation.c
View File

@ -1730,6 +1730,10 @@ isLockedRefname(ParseState *pstate, const char *refname)
* and/or namespace list. (We assume caller has checked for any
* namespace conflicts.) The RTE is always marked as unconditionally
* visible, that is, not LATERAL-only.
*
* Note: some callers know that they can find the new ParseNamespaceItem
* at the end of the pstate->p_namespace list. This is a bit ugly but not
* worth complicating this function's signature for.
*/
void
addRTEtoQuery(ParseState *pstate, RangeTblEntry *rte,

48
src/test/regress/expected/join.out
View File

@ -4103,3 +4103,51 @@ select 1 from tenk1 a, lateral (select max(a.unique1) from int4_tbl b) ss;
ERROR: aggregate functions are not allowed in FROM clause of their own query level
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:
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;
^
HINT: There is a column named "x1" in table "xx1", but it cannot be referenced from this part of the query.
update xx1 set x2 = f1 from (select * from int4_tbl where f1 = xx1.x1) ss;
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:
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:
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 lateral (select * from int4_tbl where f1 = x1) ss;
select * from xx1;
x1 | x2
----+----
(0 rows)

18
src/test/regress/sql/join.sql
View File

@ -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;