Reject cases where a query in WITH rewrites to just NOTIFY.

Since the executor can't cope with a utility statement appearing
as a node of a plan tree, we can't support cases where a rewrite
rule inserts a NOTIFY into an INSERT/UPDATE/DELETE command appearing
in a WITH clause of a larger query.  (One can imagine ways around
that, but it'd be a new feature not a bug fix, and so far there's
been no demand for it.)  RewriteQuery checked for this, but it
missed the case where the DML command rewrites to *only* a NOTIFY.
That'd lead to crashes later on in planning.  Add the missed check,
and improve the level of testing of this area.

Per bug #17094 from Yaoguang Chen.  It's been busted since WITH
was introduced, so back-patch to all supported branches.

Discussion: https://postgr.es/m/17094-bf15dff55eaf2e28@postgresql.org

diff --git a/src/backend/rewrite/rewriteHandler.c b/src/backend/rewrite/rewriteHandler.c
index efecb6e1d81f414b4d6247ae121d6335b5e0d444..14893ed5cd824b59220661ed6fe26421637b53f5 100644 (file)
--- a/src/backend/rewrite/rewriteHandler.c
+++ b/src/backend/rewrite/rewriteHandler.c
@@ -3516,15 +3516,29 @@ RewriteQuery(Query *parsetree, List *rewrite_events)
 
        /*
         * Currently we can only handle unconditional, single-statement DO
-        * INSTEAD rules correctly; we have to get exactly one Query out of
-        * the rewrite operation to stuff back into the CTE node.
+        * INSTEAD rules correctly; we have to get exactly one non-utility
+        * Query out of the rewrite operation to stuff back into the CTE node.
         */
        if (list_length(newstuff) == 1)
        {
-           /* Push the single Query back into the CTE node */
+           /* Must check it's not a utility command */
            ctequery = linitial_node(Query, newstuff);
+           if (!(ctequery->commandType == CMD_SELECT ||
+                 ctequery->commandType == CMD_UPDATE ||
+                 ctequery->commandType == CMD_INSERT ||
+                 ctequery->commandType == CMD_DELETE))
+           {
+               /*
+                * Currently it could only be NOTIFY; this error message will
+                * need work if we ever allow other utility commands in rules.
+                */
+               ereport(ERROR,
+                       (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+                        errmsg("DO INSTEAD NOTIFY rules are not supported for data-modifying statements in WITH")));
+           }
            /* WITH queries should never be canSetTag */
            Assert(!ctequery->canSetTag);
+           /* Push the single Query back into the CTE node */
            cte->ctequery = (Node *) ctequery;
        }
        else if (newstuff == NIL)

diff --git a/src/test/regress/expected/with.out b/src/test/regress/expected/with.out
index 0d506348e1c9ea073c4a081d776e1e052a0983bf..9a99bd64194672cf5287dc34205bb3adb69dcd1c 100644 (file)
--- a/src/test/regress/expected/with.out
+++ b/src/test/regress/expected/with.out
@@ -2315,6 +2315,31 @@ WITH t AS (
 )
 VALUES(FALSE);
 ERROR:  conditional DO INSTEAD rules are not supported for data-modifying statements in WITH
+CREATE OR REPLACE RULE y_rule AS ON INSERT TO y DO INSTEAD NOTHING;
+WITH t AS (
+   INSERT INTO y VALUES(0)
+)
+VALUES(FALSE);
+ERROR:  DO INSTEAD NOTHING rules are not supported for data-modifying statements in WITH
+CREATE OR REPLACE RULE y_rule AS ON INSERT TO y DO INSTEAD NOTIFY foo;
+WITH t AS (
+   INSERT INTO y VALUES(0)
+)
+VALUES(FALSE);
+ERROR:  DO INSTEAD NOTIFY rules are not supported for data-modifying statements in WITH
+CREATE OR REPLACE RULE y_rule AS ON INSERT TO y DO ALSO NOTIFY foo;
+WITH t AS (
+   INSERT INTO y VALUES(0)
+)
+VALUES(FALSE);
+ERROR:  DO ALSO rules are not supported for data-modifying statements in WITH
+CREATE OR REPLACE RULE y_rule AS ON INSERT TO y
+  DO INSTEAD (NOTIFY foo; NOTIFY bar);
+WITH t AS (
+   INSERT INTO y VALUES(0)
+)
+VALUES(FALSE);
+ERROR:  multi-statement DO INSTEAD rules are not supported for data-modifying statements in WITH
 DROP RULE y_rule ON y;
 -- check that parser lookahead for WITH doesn't cause any odd behavior
 create table foo (with baz);  -- fail, WITH is a reserved word

diff --git a/src/test/regress/sql/with.sql b/src/test/regress/sql/with.sql
index 43cd2e10af35f3511f49443b8391c71c0b3dc748..4869de4067d138f0a24fc5f9657de2e41f3428b2 100644 (file)
--- a/src/test/regress/sql/with.sql
+++ b/src/test/regress/sql/with.sql
@@ -1066,6 +1066,27 @@ WITH t AS (
    INSERT INTO y VALUES(0)
 )
 VALUES(FALSE);
+CREATE OR REPLACE RULE y_rule AS ON INSERT TO y DO INSTEAD NOTHING;
+WITH t AS (
+   INSERT INTO y VALUES(0)
+)
+VALUES(FALSE);
+CREATE OR REPLACE RULE y_rule AS ON INSERT TO y DO INSTEAD NOTIFY foo;
+WITH t AS (
+   INSERT INTO y VALUES(0)
+)
+VALUES(FALSE);
+CREATE OR REPLACE RULE y_rule AS ON INSERT TO y DO ALSO NOTIFY foo;
+WITH t AS (
+   INSERT INTO y VALUES(0)
+)
+VALUES(FALSE);
+CREATE OR REPLACE RULE y_rule AS ON INSERT TO y
+  DO INSTEAD (NOTIFY foo; NOTIFY bar);
+WITH t AS (
+   INSERT INTO y VALUES(0)
+)
+VALUES(FALSE);
 DROP RULE y_rule ON y;
 
 -- check that parser lookahead for WITH doesn't cause any odd behavior