Repair some issues with column aliases and RowExpr construction in the

presence of dropped columns.  Document the already-presumed fact that
eref aliases in relation RTEs are supposed to have entries for dropped
columns; cause the user alias structs to have such entries too, so that
there's always a one-to-one mapping to the underlying physical attnums.
Adjust expandRTE() and related code to handle the case where a column
that is part of a JOIN has been dropped.  Generalize expandRTE()'s API
so that it can be used in a couple of places that formerly rolled their
own implementation of the same logic.  Fix ruleutils.c to suppress
display of aliases for columns that were dropped since the rule was made.

1 files changed, 17 insertions, 1 deletions

diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 80230e34446..aff28bea08f 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/nodes/parsenodes.h,v 1.265 2004/08/04 21:34:24 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/nodes/parsenodes.h,v 1.266 2004/08/19 20:57:41 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -447,6 +447,22 @@ typedef struct DefElem
  *	  eref->aliasname is required to be present, and should generally be used
  *	  to identify the RTE for error messages etc.
  *
+ *	  In RELATION RTEs, the colnames in both alias and eref are indexed by
+ *	  physical attribute number; this means there must be colname entries for
+ *	  dropped columns.  When building an RTE we insert empty strings ("") for
+ *	  dropped columns.  Note however that a stored rule may have nonempty
+ *	  colnames for columns dropped since the rule was created (and for that
+ *	  matter the colnames might be out of date due to column renamings).
+ *	  The same comments apply to FUNCTION RTEs when the function's return type
+ *	  is a named composite type.
+ *
+ *	  In JOIN RTEs, the colnames in both alias and eref are one-to-one with
+ *	  joinaliasvars entries.  A JOIN RTE will omit columns of its inputs when
+ *	  those columns are known to be dropped at parse time.  Again, however,
+ *	  a stored rule might contain entries for columns dropped since the rule
+ *	  was created.  (This is only possible for columns not actually referenced
+ *	  in the rule.)
+ *
  *	  inh is TRUE for relation references that should be expanded to include
  *	  inheritance children, if the rel has any.  This *must* be FALSE for
  *	  RTEs other than RTE_RELATION entries.