Don't bother to attach column name lists to RowExprs of named types.

If a RowExpr is marked as returning a named composite type, we aren't
going to consult its colnames list; we'll use the attribute names
shown for the type in pg_attribute.  Hence, skip storing that list,
to save a few nanoseconds when copying the expression tree around.

Discussion: https://postgr.es/m/2950001.1638729947@sss.pgh.pa.us

1 files changed, 7 insertions, 9 deletions

diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
index dab5c4ff5de..439e4b4a9db 100644
--- a/src/include/nodes/primnodes.h
+++ b/src/include/nodes/primnodes.h
@@ -1052,15 +1052,13 @@ typedef struct ArrayExpr
  * than vice versa.)  It is important not to assume that length(args) is
  * the same as the number of columns logically present in the rowtype.
  *
- * colnames provides field names in cases where the names can't easily be
- * obtained otherwise.  Names *must* be provided if row_typeid is RECORDOID.
- * If row_typeid identifies a known composite type, colnames can be NIL to
- * indicate the type's cataloged field names apply.  Note that colnames can
- * be non-NIL even for a composite type, and typically is when the RowExpr
- * was created by expanding a whole-row Var.  This is so that we can retain
- * the column alias names of the RTE that the Var referenced (which would
- * otherwise be very difficult to extract from the parsetree).  Like the
- * args list, colnames is one-for-one with physical fields of the rowtype.
+ * colnames provides field names if the ROW() result is of type RECORD.
+ * Names *must* be provided if row_typeid is RECORDOID; but if it is a
+ * named composite type, colnames will be ignored in favor of using the
+ * type's cataloged field names, so colnames should be NIL.  Like the
+ * args list, colnames is defined to be one-for-one with physical fields
+ * of the rowtype (although dropped columns shouldn't appear in the
+ * RECORD case, so this fine point is currently moot).
  */
 typedef struct RowExpr
 {