Preserve column names in the execution-time tupledesc for a RowExpr.

The hstore and json datatypes both have record-conversion functions that
pay attention to column names in the composite values they're handed.
We used to not worry about inserting correct field names into tuple
descriptors generated at runtime, but given these examples it seems
useful to do so.  Observe the nicer-looking results in the regression
tests whose results changed.

catversion bump because there is a subtle change in requirements for stored
rule parsetrees: RowExprs from ROW() constructs now have to include field
names.

Andrew Dunstan and Tom Lane

1 files changed, 9 insertions, 4 deletions

diff --git a/src/backend/optimizer/util/var.c b/src/backend/optimizer/util/var.c
index 475299daddd..2bffb0a651e 100644
--- a/src/backend/optimizer/util/var.c
+++ b/src/backend/optimizer/util/var.c
@@ -783,13 +783,16 @@ flatten_join_alias_vars_mutator(Node *node,
 			/* Must expand whole-row reference */
 			RowExpr    *rowexpr;
 			List	   *fields = NIL;
+			List	   *colnames = NIL;
 			AttrNumber	attnum;
-			ListCell   *l;
+			ListCell   *lv;
+			ListCell   *ln;
 
 			attnum = 0;
-			foreach(l, rte->joinaliasvars)
+			Assert(list_length(rte->joinaliasvars) == list_length(rte->eref->colnames));
+			forboth(lv, rte->joinaliasvars, ln, rte->eref->colnames)
 			{
-				newvar = (Node *) lfirst(l);
+				newvar = (Node *) lfirst(lv);
 				attnum++;
 				/* Ignore dropped columns */
 				if (IsA(newvar, Const))
@@ -809,12 +812,14 @@ flatten_join_alias_vars_mutator(Node *node,
 				/* (also takes care of setting inserted_sublink if needed) */
 				newvar = flatten_join_alias_vars_mutator(newvar, context);
 				fields = lappend(fields, newvar);
+				/* We need the names of non-dropped columns, too */
+				colnames = lappend(colnames, copyObject((Node *) lfirst(ln)));
 			}
 			rowexpr = makeNode(RowExpr);
 			rowexpr->args = fields;
 			rowexpr->row_typeid = var->vartype;
 			rowexpr->row_format = COERCE_IMPLICIT_CAST;
-			rowexpr->colnames = NIL;
+			rowexpr->colnames = colnames;
 			rowexpr->location = var->location;
 
 			return (Node *) rowexpr;