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Fix incorrect handling of CTEs and ENRs as DML target relations. 

setTargetTable threw an error if the proposed target RangeVar's relname
matched any visible CTE or ENR.  This breaks backwards compatibility in
the CTE case, since pre-v10 we never looked for a CTE here at all, so that
CTE names did not mask regular tables.  It does seem like a good idea to
throw an error for the ENR case, though, thus causing ENRs to mask tables
for this purpose; ENRs are new in v10 so we're not breaking existing code,
and we may someday want to allow them to be the targets of DML.

To fix that, replace use of getRTEForSpecialRelationTypes, which was
overkill anyway, with use of scanNameSpaceForENR.

A second problem was that the check neglected to verify null schemaname,
so that a CTE or ENR could incorrectly be thought to match a qualified
RangeVar.  That happened because getRTEForSpecialRelationTypes relied
on its caller to have checked for null schemaname.  Even though the one
remaining caller got it right, this is obviously bug-prone, so move
the check inside getRTEForSpecialRelationTypes.

Also, revert commit 18ce3a4ab's extremely poorly thought out decision to
add a NULL return case to parserOpenTable --- without either documenting
that or adjusting any of the callers to check for it.  The current bug
seems to have arisen in part due to working around that bad idea.

In passing, remove the one-line shim functions transformCTEReference and
transformENRReference --- they don't seem to be adding any clarity or
functionality.

Per report from Hugo Mercier (via Julien Rouhaud).  Back-patch to v10
where the bug was introduced.

Thomas Munro, with minor editing by me

Discussion: https://postgr.es/m/CAOBaU_YdPVH+PTtiKSSLOiiW3mVDYsnNUekK+XPbHXiP=wrFLA@mail.gmail.com
This commit is contained in:
Tom Lane 2017-10-16 17:56:42 -04:00
parent 4211673622
commit 7421f4b89a
6 changed files with 59 additions and 63 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

74
src/backend/parser/parse_clause.c
View File

@ -62,9 +62,6 @@ static Node *transformJoinOnClause(ParseState *pstate, JoinExpr *j,
static RangeTblEntry *getRTEForSpecialRelationTypes(ParseState *pstate,
RangeVar *rv);
static RangeTblEntry *transformTableEntry(ParseState *pstate, RangeVar *r);
static RangeTblEntry *transformCTEReference(ParseState *pstate, RangeVar *r,
CommonTableExpr *cte, Index levelsup);
static RangeTblEntry *transformENRReference(ParseState *pstate, RangeVar *r);
static RangeTblEntry *transformRangeSubselect(ParseState *pstate,
RangeSubselect *r);
static RangeTblEntry *transformRangeFunction(ParseState *pstate,
@ -184,9 +181,12 @@ setTargetTable(ParseState *pstate, RangeVar *relation,
RangeTblEntry *rte;
int rtindex;
/* So far special relations are immutable; so they cannot be targets. */
rte = getRTEForSpecialRelationTypes(pstate, relation);
if (rte != NULL)
/*
* ENRs hide tables of the same name, so we need to check for them first.
* In contrast, CTEs don't hide tables (for this purpose).
*/
if (relation->schemaname == NULL &&
scanNameSpaceForENR(pstate, relation->relname))
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("relation \"%s\" cannot be the target of a modifying statement",
@ -430,35 +430,6 @@ transformTableEntry(ParseState *pstate, RangeVar *r)
return rte;
}
/*
* transformCTEReference --- transform a RangeVar that references a common
* table expression (ie, a sub-SELECT defined in a WITH clause)
*/
static RangeTblEntry *
transformCTEReference(ParseState *pstate, RangeVar *r,
CommonTableExpr *cte, Index levelsup)
{
RangeTblEntry *rte;
rte = addRangeTableEntryForCTE(pstate, cte, levelsup, r, true);
return rte;
}
/*
* transformENRReference --- transform a RangeVar that references an ephemeral
* named relation
*/
static RangeTblEntry *
transformENRReference(ParseState *pstate, RangeVar *r)
{
RangeTblEntry *rte;
rte = addRangeTableEntryForENR(pstate, r, true);
return rte;
}
/*
* transformRangeSubselect --- transform a sub-SELECT appearing in FROM
*/
@ -1071,19 +1042,32 @@ transformRangeTableSample(ParseState *pstate, RangeTableSample *rts)
return tablesample;
}
/*
* getRTEForSpecialRelationTypes
*
* If given RangeVar refers to a CTE or an EphemeralNamedRelation,
* build and return an appropriate RTE, otherwise return NULL
*/
static RangeTblEntry *
getRTEForSpecialRelationTypes(ParseState *pstate, RangeVar *rv)
{
CommonTableExpr *cte;
Index levelsup;
RangeTblEntry *rte = NULL;
RangeTblEntry *rte;
/*
* if it is a qualified name, it can't be a CTE or tuplestore reference
*/
if (rv->schemaname)
return NULL;
cte = scanNameSpaceForCTE(pstate, rv->relname, &levelsup);
if (cte)
rte = transformCTEReference(pstate, rv, cte, levelsup);
if (!rte && scanNameSpaceForENR(pstate, rv->relname))
rte = transformENRReference(pstate, rv);
rte = addRangeTableEntryForCTE(pstate, cte, levelsup, rv, true);
else if (scanNameSpaceForENR(pstate, rv->relname))
rte = addRangeTableEntryForENR(pstate, rv, true);
else
rte = NULL;
return rte;
}
@ -1119,15 +1103,11 @@ transformFromClauseItem(ParseState *pstate, Node *n,
/* Plain relation reference, or perhaps a CTE reference */
RangeVar *rv = (RangeVar *) n;
RangeTblRef *rtr;
RangeTblEntry *rte = NULL;
RangeTblEntry *rte;
int rtindex;
/*
* if it is an unqualified name, it might be a CTE or tuplestore
* reference
*/
if (!rv->schemaname)
rte = getRTEForSpecialRelationTypes(pstate, rv);
/* Check if it's a CTE or tuplestore reference */
rte = getRTEForSpecialRelationTypes(pstate, rv);
/* if not found above, must be a table reference */
if (!rte)

8
src/backend/parser/parse_relation.c
View File

@ -1159,19 +1159,13 @@ parserOpenTable(ParseState *pstate, const RangeVar *relation, int lockmode)
relation->schemaname, relation->relname)));
else
{
/*
* An unqualified name might be a named ephemeral relation.
*/
if (get_visible_ENR_metadata(pstate->p_queryEnv, relation->relname))
rel = NULL;
/*
* An unqualified name might have been meant as a reference to
* some not-yet-in-scope CTE. The bare "does not exist" message
* has proven remarkably unhelpful for figuring out such problems,
* so we take pains to offer a specific hint.
*/
else if (isFutureCTE(pstate, relation->relname))
if (isFutureCTE(pstate, relation->relname))
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_TABLE),
errmsg("relation \"%s\" does not exist",

8
src/test/regress/expected/plpgsql.out
View File

@ -5879,19 +5879,19 @@ CREATE FUNCTION transition_table_level2_bad_usage_func()
LANGUAGE plpgsql
AS $$
BEGIN
INSERT INTO d VALUES (1000000, 1000000, 'x');
INSERT INTO dx VALUES (1000000, 1000000, 'x');
RETURN NULL;
END;
$$;
CREATE TRIGGER transition_table_level2_bad_usage_trigger
AFTER DELETE ON transition_table_level2
REFERENCING OLD TABLE AS d
REFERENCING OLD TABLE AS dx
FOR EACH STATEMENT EXECUTE PROCEDURE
transition_table_level2_bad_usage_func();
DELETE FROM transition_table_level2
WHERE level2_no BETWEEN 301 AND 305;
ERROR: relation "d" cannot be the target of a modifying statement
CONTEXT: SQL statement "INSERT INTO d VALUES (1000000, 1000000, 'x')"
ERROR: relation "dx" cannot be the target of a modifying statement
CONTEXT: SQL statement "INSERT INTO dx VALUES (1000000, 1000000, 'x')"
PL/pgSQL function transition_table_level2_bad_usage_func() line 3 at SQL statement
DROP TRIGGER transition_table_level2_bad_usage_trigger
ON transition_table_level2;

18
src/test/regress/expected/with.out
View File

@ -2273,5 +2273,19 @@ with ordinality as (select 1 as x) select * from ordinality;
(1 row)
-- check sane response to attempt to modify CTE relation
WITH d AS (SELECT 42) INSERT INTO d VALUES (1);
ERROR: relation "d" cannot be the target of a modifying statement
WITH test AS (SELECT 42) INSERT INTO test VALUES (1);
ERROR: relation "test" does not exist
LINE 1: WITH test AS (SELECT 42) INSERT INTO test VALUES (1);
^
-- check response to attempt to modify table with same name as a CTE (perhaps
-- surprisingly it works, because CTEs don't hide tables from data-modifying
-- statements)
create table test (i int);
with test as (select 42) insert into test select * from test;
select * from test;
i
----
42
(1 row)
drop table test;

4
src/test/regress/sql/plpgsql.sql
View File

@ -4678,14 +4678,14 @@ CREATE FUNCTION transition_table_level2_bad_usage_func()
LANGUAGE plpgsql
AS $$
BEGIN
INSERT INTO d VALUES (1000000, 1000000, 'x');
INSERT INTO dx VALUES (1000000, 1000000, 'x');
RETURN NULL;
END;
$$;
CREATE TRIGGER transition_table_level2_bad_usage_trigger
AFTER DELETE ON transition_table_level2
REFERENCING OLD TABLE AS d
REFERENCING OLD TABLE AS dx
FOR EACH STATEMENT EXECUTE PROCEDURE
transition_table_level2_bad_usage_func();

10
src/test/regress/sql/with.sql
View File

@ -1030,4 +1030,12 @@ create table foo (with ordinality); -- fail, WITH is a reserved word
with ordinality as (select 1 as x) select * from ordinality;
-- check sane response to attempt to modify CTE relation
WITH d AS (SELECT 42) INSERT INTO d VALUES (1);
WITH test AS (SELECT 42) INSERT INTO test VALUES (1);
-- check response to attempt to modify table with same name as a CTE (perhaps
-- surprisingly it works, because CTEs don't hide tables from data-modifying
-- statements)
create table test (i int);
with test as (select 42) insert into test select * from test;
select * from test;
drop table test;