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/20161205143037.4377.60754@wrigleys.postgresql.org
Discussion: https://postgr.es/m/27429.1480968538@sss.pgh.pa.us

1 files changed, 24 insertions, 70 deletions

diff --git a/src/backend/parser/parse_relation.c b/src/backend/parser/parse_relation.c
index 1e3ecbc51ef..58f70508fea 100644
--- a/src/backend/parser/parse_relation.c
+++ b/src/backend/parser/parse_relation.c
@@ -1635,7 +1635,9 @@ addRangeTableEntryForFunction(ParseState *pstate,
 RangeTblEntry *
 addRangeTableEntryForValues(ParseState *pstate,
 							List *exprs,
-							List *collations,
+							List *coltypes,
+							List *coltypmods,
+							List *colcollations,
 							Alias *alias,
 							bool lateral,
 							bool inFromCl)
@@ -1652,7 +1654,9 @@ addRangeTableEntryForValues(ParseState *pstate,
 	rte->relid = InvalidOid;
 	rte->subquery = NULL;
 	rte->values_lists = exprs;
-	rte->values_collations = collations;
+	rte->coltypes = coltypes;
+	rte->coltypmods = coltypmods;
+	rte->colcollations = colcollations;
 	rte->alias = alias;
 
 	eref = alias ? copyObject(alias) : makeAlias(refname, NIL);
@@ -1822,9 +1826,9 @@ addRangeTableEntryForCTE(ParseState *pstate,
 					 parser_errposition(pstate, rv->location)));
 	}
 
-	rte->ctecoltypes = cte->ctecoltypes;
-	rte->ctecoltypmods = cte->ctecoltypmods;
-	rte->ctecolcollations = cte->ctecolcollations;
+	rte->coltypes = cte->ctecoltypes;
+	rte->coltypmods = cte->ctecoltypmods;
+	rte->colcollations = cte->ctecolcollations;
 
 	rte->alias = alias;
 	if (alias)
@@ -2153,46 +2157,6 @@ expandRTE(RangeTblEntry *rte, int rtindex, int sublevels_up,
 				}
 			}
 			break;
-		case RTE_VALUES:
-			{
-				/* Values RTE */
-				ListCell   *aliasp_item = list_head(rte->eref->colnames);
-				ListCell   *lcv;
-				ListCell   *lcc;
-
-				varattno = 0;
-				forboth(lcv, (List *) linitial(rte->values_lists),
-						lcc, rte->values_collations)
-				{
-					Node	   *col = (Node *) lfirst(lcv);
-					Oid			colcollation = lfirst_oid(lcc);
-
-					varattno++;
-					if (colnames)
-					{
-						/* Assume there is one alias per column */
-						char	   *label = strVal(lfirst(aliasp_item));
-
-						*colnames = lappend(*colnames,
-											makeString(pstrdup(label)));
-						aliasp_item = lnext(aliasp_item);
-					}
-
-					if (colvars)
-					{
-						Var		   *varnode;
-
-						varnode = makeVar(rtindex, varattno,
-										  exprType(col),
-										  exprTypmod(col),
-										  colcollation,
-										  sublevels_up);
-						varnode->location = location;
-						*colvars = lappend(*colvars, varnode);
-					}
-				}
-			}
-			break;
 		case RTE_JOIN:
 			{
 				/* Join RTE */
@@ -2262,17 +2226,19 @@ expandRTE(RangeTblEntry *rte, int rtindex, int sublevels_up,
 				}
 			}
 			break;
+		case RTE_VALUES:
 		case RTE_CTE:
 			{
+				/* Values or CTE RTE */
 				ListCell   *aliasp_item = list_head(rte->eref->colnames);
 				ListCell   *lct;
 				ListCell   *lcm;
 				ListCell   *lcc;
 
 				varattno = 0;
-				forthree(lct, rte->ctecoltypes,
-						 lcm, rte->ctecoltypmods,
-						 lcc, rte->ctecolcollations)
+				forthree(lct, rte->coltypes,
+						 lcm, rte->coltypmods,
+						 lcc, rte->colcollations)
 				{
 					Oid			coltype = lfirst_oid(lct);
 					int32		coltypmod = lfirst_int(lcm);
@@ -2285,7 +2251,8 @@ expandRTE(RangeTblEntry *rte, int rtindex, int sublevels_up,
 						/* Assume there is one alias per output column */
 						char	   *label = strVal(lfirst(aliasp_item));
 
-						*colnames = lappend(*colnames, makeString(pstrdup(label)));
+						*colnames = lappend(*colnames,
+											makeString(pstrdup(label)));
 						aliasp_item = lnext(aliasp_item);
 					}
 
@@ -2296,6 +2263,8 @@ expandRTE(RangeTblEntry *rte, int rtindex, int sublevels_up,
 						varnode = makeVar(rtindex, varattno,
 										  coltype, coltypmod, colcoll,
 										  sublevels_up);
+						varnode->location = location;
+
 						*colvars = lappend(*colvars, varnode);
 					}
 				}
@@ -2654,22 +2623,6 @@ get_rte_attribute_type(RangeTblEntry *rte, AttrNumber attnum,
 								rte->eref->aliasname)));
 			}
 			break;
-		case RTE_VALUES:
-			{
-				/* Values RTE --- get type info from first sublist */
-				/* collation is stored separately, though */
-				List	   *collist = (List *) linitial(rte->values_lists);
-				Node	   *col;
-
-				if (attnum < 1 || attnum > list_length(collist))
-					elog(ERROR, "values list %s does not have attribute %d",
-						 rte->eref->aliasname, attnum);
-				col = (Node *) list_nth(collist, attnum - 1);
-				*vartype = exprType(col);
-				*vartypmod = exprTypmod(col);
-				*varcollid = list_nth_oid(rte->values_collations, attnum - 1);
-			}
-			break;
 		case RTE_JOIN:
 			{
 				/*
@@ -2685,13 +2638,14 @@ get_rte_attribute_type(RangeTblEntry *rte, AttrNumber attnum,
 				*varcollid = exprCollation(aliasvar);
 			}
 			break;
+		case RTE_VALUES:
 		case RTE_CTE:
 			{
-				/* CTE RTE --- get type info from lists in the RTE */
-				Assert(attnum > 0 && attnum <= list_length(rte->ctecoltypes));
-				*vartype = list_nth_oid(rte->ctecoltypes, attnum - 1);
-				*vartypmod = list_nth_int(rte->ctecoltypmods, attnum - 1);
-				*varcollid = list_nth_oid(rte->ctecolcollations, attnum - 1);
+				/* VALUES or CTE RTE --- get type info from lists in the RTE */
+				Assert(attnum > 0 && attnum <= list_length(rte->coltypes));
+				*vartype = list_nth_oid(rte->coltypes, attnum - 1);
+				*vartypmod = list_nth_int(rte->coltypmods, attnum - 1);
+				*varcollid = list_nth_oid(rte->colcollations, attnum - 1);
 			}
 			break;
 		default: