In transformRowExpr(), check for too many columns in the row.

A RowExpr with more than MaxTupleAttributeNumber columns would fail at
execution anyway, since we cannot form a tuple datum with more than that
many columns.  While heap_form_tuple() has a check for too many columns,
it emerges that there are some intermediate bits of code that don't
check and can be driven to failure with sufficiently many columns.
Checking this at parse time seems like the most appropriate place to
install a defense, since we already check SELECT list length there.

While at it, make the SELECT-list-length error use the same errcode
(TOO_MANY_COLUMNS) as heap_form_tuple does, rather than the generic
PROGRAM_LIMIT_EXCEEDED.

Per bug #17561 from Egor Chindyaskin.  The given test case crashes
in all supported branches (and probably a lot further back),
so patch all.

Discussion: https://postgr.es/m/17561-80350151b9ad2ad4@postgresql.org

diff --git a/src/backend/parser/parse_expr.c b/src/backend/parser/parse_expr.c
index 9f567f4bf414a9695393a1f7566767709f583a57..059cb7097c7637e756d361816e7c1dd1f5e68ad3 100644 (file)
--- a/src/backend/parser/parse_expr.c
+++ b/src/backend/parser/parse_expr.c
@@ -2140,6 +2140,14 @@ transformRowExpr(ParseState *pstate, RowExpr *r, bool allowDefault)
    newr->args = transformExpressionList(pstate, r->args,
                                         pstate->p_expr_kind, allowDefault);
 
+   /* Disallow more columns than will fit in a tuple */
+   if (list_length(newr->args) > MaxTupleAttributeNumber)
+       ereport(ERROR,
+               (errcode(ERRCODE_TOO_MANY_COLUMNS),
+                errmsg("ROW expressions can have at most %d entries",
+                       MaxTupleAttributeNumber),
+                parser_errposition(pstate, r->location)));
+
    /* Barring later casting, we consider the type RECORD */
    newr->row_typeid = RECORDOID;
    newr->row_format = COERCE_IMPLICIT_CAST;

diff --git a/src/backend/parser/parse_node.c b/src/backend/parser/parse_node.c
index 4d39cf959450b3392306cc0dadf5e76ed32ac766..4014db4b80f9b2c1a1cfdd5ee9087721b35753ce 100644 (file)
--- a/src/backend/parser/parse_node.c
+++ b/src/backend/parser/parse_node.c
@@ -82,7 +82,7 @@ free_parsestate(ParseState *pstate)
     */
    if (pstate->p_next_resno - 1 > MaxTupleAttributeNumber)
        ereport(ERROR,
-               (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+               (errcode(ERRCODE_TOO_MANY_COLUMNS),
                 errmsg("target lists can have at most %d entries",
                        MaxTupleAttributeNumber)));