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

Neil Conway · Neil Conway · commit be8100d64ec9 · 2005-12-11T10:54:28.000Z
Patch from Pavel Stehule, minor fixups by myself.
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
@@ -1,5 +1,5 @@
 <!--
-$PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.297 2005/12/03 16:45:05 momjian Exp $
+$PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.298 2005/12/11 10:54:27 neilc Exp $
 PostgreSQL documentation
 -->
 
@@ -345,16 +345,24 @@ PostgreSQL documentation
     <indexterm>
      <primary>IS DISTINCT FROM</primary>
     </indexterm>
+    <indexterm>
+     <primary>IS NOT DISTINCT FROM</primary>
+    </indexterm>
     The ordinary comparison operators yield null (signifying <quote>unknown</>)
     when either input is null.  Another way to do comparisons is with the
     <literal>IS DISTINCT FROM</literal> construct:
 <synopsis>
 <replaceable>expression</replaceable> IS DISTINCT FROM <replaceable>expression</replaceable>
+<replaceable>expression</replaceable> IS NOT DISTINCT FROM <replaceable>expression</replaceable>
 </synopsis>
-    For non-null inputs this is the same as the <literal>&lt;&gt;</> 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 <quote>unknown</>.
+    For non-null inputs, <literal>IS DISTINCT FROM</literal> this is
+    the same as the <literal>&lt;&gt;</> operator.  However, when both
+    inputs are null it will return false, and when just one input is
+    null it will return true.  Similarly, <literal>IS NOT DISTINCT
+    FROM</literal> is identical to <literal>=</literal> 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 <quote>unknown</>.
    </para>
 
    <para>
diff --git 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
@@ -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
@@ -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";

Original file line number	Diff line number	Diff line change
`@@ -11,7 +11,7 @@`
`11`	`11`	`*`
`12`	`12`	`*`
`13`	`13`	`* IDENTIFICATION`
`14`		`- * $PostgreSQL: pgsql/src/backend/parser/gram.y,v 2.516 2005/11/28 04:35:31 tgl Exp $`
	`14`	`+ * $PostgreSQL: pgsql/src/backend/parser/gram.y,v 2.517 2005/12/11 10:54:27 neilc Exp $`
`15`	`15`	`*`
`16`	`16`	`* HISTORY`
`17`	`17`	`* AUTHOR DATE MAJOR EVENT`
`@@ -6715,6 +6715,13 @@ a_expr: c_expr { $$ = $1; }`
`6715`	`6715`	`{`
`6716`	`6716`	`$$ = (Node *) makeSimpleA_Expr(AEXPR_DISTINCT, "=", $1, $5);`
`6717`	`6717`	`}`
	`6718`	`+ \| a_expr IS NOT DISTINCT FROM a_expr %prec IS`
	`6719`	`+ {`
	`6720`	`+ $$ = (Node *) makeA_Expr(AEXPR_NOT, NIL, NULL,`
	`6721`	`+ (Node *) makeSimpleA_Expr(AEXPR_DISTINCT,`
	`6722`	`+ "=", $1, $6));`
	`6723`	`+`
	`6724`	`+ }`
`6718`	`6725`	`\| a_expr IS OF '(' type_list ')' %prec IS`
`6719`	`6726`	`{`
`6720`	`6727`	`$$ = (Node ) makeSimpleA_Expr(AEXPR_OF, "=", $1, (Node ) $5);`
`@@ -6880,6 +6887,11 @@ b_expr: c_expr`
`6880`	`6887`	`{`
`6881`	`6888`	`$$ = (Node *) makeSimpleA_Expr(AEXPR_DISTINCT, "=", $1, $5);`
`6882`	`6889`	`}`
	`6890`	`+ \| b_expr IS NOT DISTINCT FROM b_expr %prec IS`
	`6891`	`+ {`
	`6892`	`+ $$ = (Node *) makeA_Expr(AEXPR_NOT, NIL,`
	`6893`	`+ NULL, (Node *) makeSimpleA_Expr(AEXPR_DISTINCT, "=", $1, $6));`
	`6894`	`+ }`
`6883`	`6895`	`\| b_expr IS OF '(' type_list ')' %prec IS`
`6884`	`6896`	`{`
`6885`	`6897`	`$$ = (Node ) makeSimpleA_Expr(AEXPR_OF, "=", $1, (Node ) $5);`