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

diff --git a/src/backend/parser/parse_clause.c b/src/backend/parser/parse_clause.c
index 9ff80b8b403552e1de5182fe199de0ee66703a4b..af99e65aa7df2eaa43bd29e5db6336dab6c1d181 100644 (file)
--- a/src/backend/parser/parse_clause.c
+++ b/src/backend/parser/parse_clause.c
@@ -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)

diff --git a/src/backend/parser/parse_relation.c b/src/backend/parser/parse_relation.c
index a0ad01104a829044c982d8db3dfffc370747d5f2..0056b1944363949e37e10a6376c9b8a98c646fe2 100644 (file)
--- a/src/backend/parser/parse_relation.c
+++ b/src/backend/parser/parse_relation.c
@@ -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",

diff --git a/src/test/regress/expected/plpgsql.out b/src/test/regress/expected/plpgsql.out
index 71099969a47e8db16478db61f3d476ca4859e5d0..36ecedac5e1abd6f922e81d0b6c76f00a7d820f8 100644 (file)
--- a/src/test/regress/expected/plpgsql.out
+++ b/src/test/regress/expected/plpgsql.out
@@ -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;

diff --git a/src/test/regress/expected/with.out b/src/test/regress/expected/with.out
index fdcc4970a130496711b31eb22920cf86babdd8eb..3e2b34c6fcdd92aaf468b693c295faf3436c54c3 100644 (file)
--- a/src/test/regress/expected/with.out
+++ b/src/test/regress/expected/with.out
@@ -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;

diff --git a/src/test/regress/sql/plpgsql.sql b/src/test/regress/sql/plpgsql.sql
index 771d68282eed8c744f77f9bcf955ce23202ee835..d025605b1b1c534f94fc5932bbe636ea511aef69 100644 (file)
--- a/src/test/regress/sql/plpgsql.sql
+++ b/src/test/regress/sql/plpgsql.sql
@@ -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();
 

diff --git a/src/test/regress/sql/with.sql b/src/test/regress/sql/with.sql
index 8ae5184d0f17cc4c2e805aad0280ae90134fe41f..baf65488a8edd9efd078f9422cd2cd8987b6f5a1 100644 (file)
--- a/src/test/regress/sql/with.sql
+++ b/src/test/regress/sql/with.sql
@@ -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;