Fix reporting of column typmods for multi-row VALUES constructs.

expandRTE() and get_rte_attribute_type() reported the exprType() and
exprTypmod() values of the expressions in the first row of the VALUES as
being the column type/typmod returned by the VALUES RTE.  That's fine for
the data type, since we coerce all expressions in a column to have the same
common type.  But we don't coerce them to have a common typmod, so it was
possible for rows after the first one to return values that violate the
claimed column typmod.  This leads to the incorrect result seen in bug
#14448 from Hassan Mahmood, as well as some other corner-case misbehaviors.

The desired behavior is the same as we use in other type-unification
cases: report the common typmod if there is one, but otherwise return -1
indicating no particular constraint.  It's cheap for transformValuesClause
to determine the common typmod while transforming a multi-row VALUES, but
it'd be less cheap for expandRTE() and get_rte_attribute_type() to
re-determine that info every time they're asked --- possibly a lot less
cheap, if the VALUES has many rows.  Therefore, the best fix is to record
the common typmods explicitly in a list in the VALUES RTE, as we were
already doing for column collations.  This looks quite a bit like what
we're doing for CTE RTEs, so we can save a little bit of space and code by
unifying the representation for those two RTE types.  They both now share
coltypes/coltypmods/colcollations fields.  (At some point it might seem
desirable to populate those fields for all RTE types; but right now it
looks like constructing them for other RTE types would add more code and
cycles than it would save.)

The RTE change requires a catversion bump, so this fix is only usable
in HEAD.  If we fix this at all in the back branches, the patch will
need to look quite different.

Report: https://postgr.es/m/[email protected]
Discussion: https://postgr.es/m/[email protected]

1 files changed, 6 insertions, 4 deletions

diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index 0d858f59206..7258c0357db 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -2841,15 +2841,17 @@ _outRangeTblEntry(StringInfo str, const RangeTblEntry *node)
 			break;
 		case RTE_VALUES:
 			WRITE_NODE_FIELD(values_lists);
-			WRITE_NODE_FIELD(values_collations);
+			WRITE_NODE_FIELD(coltypes);
+			WRITE_NODE_FIELD(coltypmods);
+			WRITE_NODE_FIELD(colcollations);
 			break;
 		case RTE_CTE:
 			WRITE_STRING_FIELD(ctename);
 			WRITE_UINT_FIELD(ctelevelsup);
 			WRITE_BOOL_FIELD(self_reference);
-			WRITE_NODE_FIELD(ctecoltypes);
-			WRITE_NODE_FIELD(ctecoltypmods);
-			WRITE_NODE_FIELD(ctecolcollations);
+			WRITE_NODE_FIELD(coltypes);
+			WRITE_NODE_FIELD(coltypmods);
+			WRITE_NODE_FIELD(colcollations);
 			break;
 		default:
 			elog(ERROR, "unrecognized RTE kind: %d", (int) node->rtekind);