Implement IS NOT DISTINCT FROM, update the regression tests and docs.

Patch from Pavel Stehule, minor fixups by myself.

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index f3df61817981f7d455d268291d8fb9be4652b0c5..8e60ba63c81e14d23f8674416dfb7e869d202e21 100644 (file)
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -1,5 +1,5 @@
 
 
@@ -345,16 +345,24 @@ PostgreSQL documentation
     
      IS DISTINCT FROM
     
+    
+     IS NOT DISTINCT FROM
+    
     The ordinary comparison operators yield null (signifying unknown)
     when either input is null.  Another way to do comparisons is with the
     IS DISTINCT FROM construct:
 
 expression IS DISTINCT FROM expression
+expression IS NOT DISTINCT FROM expression
 
-    For non-null inputs this is the same as the <> operator.
-    However, when both inputs are null it will return false, and when just
-    one input is null it will return true.  Thus it effectively acts as though
-    null were a normal data value, rather than unknown.
+    For non-null inputs, IS DISTINCT FROM this is
+    the same as the <> operator.  However, when both
+    inputs are null it will return false, and when just one input is
+    null it will return true.  Similarly, IS NOT DISTINCT
+    FROM is identical to = for non-null
+    inputs, returns true when both inputs are null, and false
+    otherwise. Thus, these constructs effectively act as though null
+    were a normal data value, rather than unknown.
    
 
    

diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 876e8b53ff5ae9e171d6f6b92d4cbc1c7dedc33b..16fdde7b9bca965144ebba8c432c9b7c113fc8f0 100644 (file)
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -11,7 +11,7 @@
  *
  *
  * IDENTIFICATION
- *   $PostgreSQL: pgsql/src/backend/parser/gram.y,v 2.516 2005/11/28 04:35:31 tgl Exp $
+ *   $PostgreSQL: pgsql/src/backend/parser/gram.y,v 2.517 2005/12/11 10:54:27 neilc Exp $
  *
  * HISTORY
  *   AUTHOR            DATE            MAJOR EVENT
@@ -6715,6 +6715,13 @@ a_expr:      c_expr                                  { $$ = $1; }
                {
                    $$ = (Node *) makeSimpleA_Expr(AEXPR_DISTINCT, "=", $1, $5);
                }
+           | a_expr IS NOT DISTINCT FROM a_expr        %prec IS
+               {
+                   $$ = (Node *) makeA_Expr(AEXPR_NOT, NIL, NULL,
+                                   (Node *) makeSimpleA_Expr(AEXPR_DISTINCT,
+                                                             "=", $1, $6));
+
+               }
            | a_expr IS OF '(' type_list ')'            %prec IS
                {
                    $$ = (Node *) makeSimpleA_Expr(AEXPR_OF, "=", $1, (Node *) $5);
@@ -6880,6 +6887,11 @@ b_expr:      c_expr
                {
                    $$ = (Node *) makeSimpleA_Expr(AEXPR_DISTINCT, "=", $1, $5);
                }
+           | b_expr IS NOT DISTINCT FROM b_expr    %prec IS
+               {
+                   $$ = (Node *) makeA_Expr(AEXPR_NOT, NIL,
+                       NULL, (Node *) makeSimpleA_Expr(AEXPR_DISTINCT, "=", $1, $6));
+               }
            | b_expr IS OF '(' type_list ')'    %prec IS
                {
                    $$ = (Node *) makeSimpleA_Expr(AEXPR_OF, "=", $1, (Node *) $5);

diff --git a/src/test/regress/expected/select_distinct.out b/src/test/regress/expected/select_distinct.out
index 019638ed176c4a50ff70e51a099c88d121a05903..abe34ae7ae5966a54d21f216cfdade115667ae43 100644 (file)
--- a/src/test/regress/expected/select_distinct.out
+++ b/src/test/regress/expected/select_distinct.out
@@ -195,3 +195,28 @@ SELECT null IS DISTINCT FROM null as "no";
  f
 (1 row)
 
+-- ANSI SQL 2003 form
+SELECT 1 IS NOT DISTINCT FROM 2 as "no";
+ no 
+----
+ f
+(1 row)
+
+SELECT 2 IS NOT DISTINCT FROM 2 as "yes";
+ yes 
+-----
+ t
+(1 row)
+
+SELECT 2 IS NOT DISTINCT FROM null as "no";
+ no 
+----
+ f
+(1 row)
+
+SELECT null IS NOT DISTINCT FROM null as "yes";
+ yes 
+-----
+ t
+(1 row)
+

diff --git a/src/test/regress/sql/select_distinct.sql b/src/test/regress/sql/select_distinct.sql
index 94032c312eed5aff51f5ee7404e7851e0c8ad3f7..c4a63aaf16fd9788b10523cc4d173bf31520bf65 100644 (file)
--- a/src/test/regress/sql/select_distinct.sql
+++ b/src/test/regress/sql/select_distinct.sql
@@ -56,3 +56,9 @@ SELECT 1 IS DISTINCT FROM 2 as "yes";
 SELECT 2 IS DISTINCT FROM 2 as "no";
 SELECT 2 IS DISTINCT FROM null as "yes";
 SELECT null IS DISTINCT FROM null as "no";
+
+-- ANSI SQL 2003 form
+SELECT 1 IS NOT DISTINCT FROM 2 as "no";
+SELECT 2 IS NOT DISTINCT FROM 2 as "yes";
+SELECT 2 IS NOT DISTINCT FROM null as "no";
+SELECT null IS NOT DISTINCT FROM null as "yes";