I checked the alter table code, and started suspecting the relation

cache.  I found if I manually added a line to flush the whole relation
cache, the assert error disappeared.  Looking through the code, I found
that the relation cache is flushed at the end of each query if the
reference count is zero for the relation.  However, printf's showed that
the rd_relcnt(reference count) for the accessed query was not returning
to zero after each query.

It turns out the parser was doing a heap_ropen in parser/analyze.c to
get information about the table's columns, but was not doing a
heap_close.

This was causing the query after the ALTER TABLE ADD to see the old
table structure, and the executor's assert was reporting the problem.

1 files changed, 2 insertions, 2 deletions

diff --git a/src/include/parser/parse_state.h b/src/include/parser/parse_state.h
index 9636462536d..e3bba8ee98e 100644
--- a/src/include/parser/parse_state.h
+++ b/src/include/parser/parse_state.h
@@ -4,7 +4,7 @@
  *
  * Copyright (c) 1994, Regents of the University of California
  *
- * $Id: parse_state.h,v 1.1 1996/08/28 07:23:56 scrappy Exp $
+ * $Id: parse_state.h,v 1.2 1996/10/13 04:26:39 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -16,7 +16,7 @@
 typedef struct ParseState {
     int 	p_last_resno; 
     List 	*p_target_resnos;
-    Relation 	parser_current_rel;
+    Relation 	p_parser_current_rel;
     List 	*p_rtable;
     int 	p_query_is_rule;
     int		p_numAgg;