Implement the IS DISTINCT FROM operator per SQL99.

Reused the Expr node to hold DISTINCT which strongly resembles
 the existing OP info. Define DISTINCT_EXPR which strongly resembles
 the existing OPER_EXPR opType, but with handling for NULLs required
 by SQL99.
We have explicit support for single-element DISTINCT comparisons
 all the way through to the executor. But, multi-element DISTINCTs
 are handled by expanding into a comparison tree in gram.y as is done for
 other row comparisons. Per discussions, it might be desirable to move
 this into one or more purpose-built nodes to be handled in the backend.
Define the optional ROW keyword and token per SQL99.
 This allows single-element row constructs, which were formerly disallowed
 due to shift/reduce conflicts with parenthesized a_expr clauses.
Define the SQL99 TREAT() function. Currently, use as a synonym for CAST().

1 files changed, 16 insertions, 1 deletions

diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 2c15bf916b9..bcdfe313b6b 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -3,7 +3,7 @@
  *				back to source text
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/utils/adt/ruleutils.c,v 1.108 2002/06/13 03:40:49 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/utils/adt/ruleutils.c,v 1.109 2002/07/04 15:24:07 thomas Exp $
  *
  *	  This software is copyrighted by Jan Wieck - Hamburg.
  *
@@ -1626,6 +1626,21 @@ get_rule_expr(Node *node, deparse_context *context)
 						get_oper_expr(expr, context);
 						break;
 
+					case DISTINCT_EXPR:
+						appendStringInfoChar(buf, '(');
+						Assert(length(args) == 2);
+						{
+							/* binary operator */
+							Node   *arg1 = (Node *) lfirst(args);
+							Node   *arg2 = (Node *) lsecond(args);
+
+							get_rule_expr(arg1, context);
+							appendStringInfo(buf, " IS DISTINCT FROM ");
+							get_rule_expr(arg2, context);
+						}
+						appendStringInfoChar(buf, ')');
+						break;
+
 					case FUNC_EXPR:
 						get_func_expr(expr, context);
 						break;