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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. We fixed this in HEAD by deriving the typmods during transformValuesClause and storing them in the RTE, but that's not a feasible solution in the back branches. Instead, just use a brute-force approach of determining the correct common typmod during expandRTE() and get_rte_attribute_type(). Simple testing says that that doesn't really cost much, at least not in common cases where expandRTE() is only used once per query. It turns out that get_rte_attribute_type() is typically never used at all on VALUES RTEs, so the inefficiency there is of no great concern. Report: https://postgr.es/m/20161205143037.4377.60754@wrigleys.postgresql.org Discussion: https://postgr.es/m/27429.1480968538@sss.pgh.pa.us