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, 12 insertions, 1 deletions

diff --git a/src/backend/parser/parse_expr.c b/src/backend/parser/parse_expr.c
index f911238ecce..ac4a5b6e5f3 100644
--- a/src/backend/parser/parse_expr.c
+++ b/src/backend/parser/parse_expr.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/parser/parse_expr.c,v 1.119 2002/06/20 20:29:32 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/parser/parse_expr.c,v 1.120 2002/07/04 15:24:01 thomas Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -271,6 +271,17 @@ transformExpr(ParseState *pstate, Node *expr)
 							result = (Node *) expr;
 						}
 						break;
+					case DISTINCT:
+						{
+							Node	   *lexpr = transformExpr(pstate,
+															  a->lexpr);
+							Node	   *rexpr = transformExpr(pstate,
+															  a->rexpr);
+							result = (Node *) make_op(a->name,
+													  lexpr,
+													  rexpr);
+							((Expr *)result)->opType = DISTINCT_EXPR;
+						}
 				}
 				break;
 			}