Allow an optional alias for the target table to be specified for UPDATE

and DELETE. If specified, the alias must be used instead of the full
table name. Also, the alias currently cannot be used in the SET clause
of UPDATE.

Patch from Atsushi Ogawa, various editorialization by Neil Conway.
Along the way, make the rowtypes regression test pass if add_missing_from
is enabled, and add a new (skeletal) regression test for DELETE.

doc/src/sgml/ref/delete.sgml

 <!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/delete.sgml,v 1.25 2005/11/01 21:09:50 tgl Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/delete.sgml,v 1.26 2006/01/22 05:20:33 neilc Exp $
 PostgreSQL documentation
 -->
 
@@ -20,7 +20,7 @@ PostgreSQL documentation
 
  <refsynopsisdiv>
 <synopsis>
-DELETE FROM [ ONLY ] <replaceable class="PARAMETER">table</replaceable>
+DELETE FROM [ ONLY ] <replaceable class="PARAMETER">table</replaceable> [ [ AS ] <replaceable class="parameter">alias</replaceable> ]
     [ USING <replaceable class="PARAMETER">usinglist</replaceable> ]
     [ WHERE <replaceable class="PARAMETER">condition</replaceable> ]
 </synopsis>
@@ -91,6 +91,19 @@ DELETE FROM [ ONLY ] <replaceable class="PARAMETER">table</replaceable>
     </listitem>
    </varlistentry>
 
+   <varlistentry>
+    <term><replaceable class="parameter">alias</replaceable></term>
+    <listitem>
+     <para>
+      A substitute name for the target table. When an alias is
+      provided, it completely hides the actual name of the table.  For
+      example, given <literal>DELETE FROM foo AS f</>, the remainder
+      of the <command>DELETE</command> statement must refer to this
+      table as <literal>f</> not <literal>foo</>.
+     </para>
+    </listitem>
+   </varlistentry>
+
    <varlistentry>
     <term><replaceable class="PARAMETER">usinglist</replaceable></term>
     <listitem>

doc/src/sgml/ref/update.sgml

 <!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/update.sgml,v 1.34 2006/01/19 23:09:42 momjian Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/update.sgml,v 1.35 2006/01/22 05:20:33 neilc Exp $
 PostgreSQL documentation
 -->
 
@@ -20,7 +20,8 @@ PostgreSQL documentation
 
  <refsynopsisdiv>
 <synopsis>
-UPDATE [ ONLY ] <replaceable class="PARAMETER">table</replaceable> SET <replaceable class="PARAMETER">column</replaceable> = { <replaceable class="PARAMETER">expression</replaceable> | DEFAULT } [, ...]
+UPDATE [ ONLY ] <replaceable class="PARAMETER">table</replaceable> [ [ AS ] <replaceable class="parameter">alias</replaceable> ]
+    SET <replaceable class="PARAMETER">column</replaceable> = { <replaceable class="PARAMETER">expression</replaceable> | DEFAULT } [, ...]
     [ FROM <replaceable class="PARAMETER">fromlist</replaceable> ]
     [ WHERE <replaceable class="PARAMETER">condition</replaceable> ]
 </synopsis>
@@ -73,6 +74,21 @@ UPDATE [ ONLY ] <replaceable class="PARAMETER">table</replaceable> SET <replacea
     </listitem>
    </varlistentry>
 
+   <varlistentry>
+    <term><replaceable class="parameter">alias</replaceable></term>
+    <listitem>
+     <para>
+      A substitute name for the target table. When an alias is
+      provided, it completely hides the actual name of the table.  For
+      example, given <literal>UPDATE foo AS f</>, the remainder of the
+      <command>UPDATE</command> statement must refer to this table as
+      <literal>f</> not <literal>foo</>. You cannot use the alias in
+      the <literal>SET</literal> clause.  For example, <literal>SET
+      f.col = 1</> is invalid.
+     </para>
+    </listitem>
+   </varlistentry>
+
    <varlistentry>
     <term><replaceable class="PARAMETER">column</replaceable></term>
     <listitem>

doc/src/sgml/regress.sgml

-<!-- $PostgreSQL: pgsql/doc/src/sgml/regress.sgml,v 1.49 2005/10/18 21:43:33 tgl Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/regress.sgml,v 1.50 2006/01/22 05:20:32 neilc Exp $ -->
 
  <chapter id="regress">
   <title id="regress-title">Regression Tests</title>
@@ -49,7 +49,7 @@ gmake check
 <screen>
 <computeroutput>
 ======================
- All 98 tests passed.
+ All 100 tests passed.
 ======================
 </computeroutput>
 </screen>

src/backend/parser/gram.y

@@ -11,7 +11,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/parser/gram.y,v 2.522 2006/01/21 02:16:19 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/parser/gram.y,v 2.523 2006/01/22 05:20:33 neilc Exp $
  *
  * HISTORY
  *	  AUTHOR			DATE			MAJOR EVENT
@@ -291,6 +291,7 @@ static void doNegateFloat(Value *v);
 %type <node>	table_ref
 %type <jexpr>	joined_table
 %type <range>	relation_expr
+%type <range>	relation_expr_opt_alias
 %type <target>	target_el insert_target_el update_target_el insert_column_item
 
 %type <typnam>	Typename SimpleTypename ConstTypename
@@ -5148,7 +5149,8 @@ insert_column_item:
  *
  *****************************************************************************/
 
-DeleteStmt: DELETE_P FROM relation_expr using_clause where_clause
+DeleteStmt: DELETE_P FROM relation_expr_opt_alias
+			using_clause where_clause
 				{
 					DeleteStmt *n = makeNode(DeleteStmt);
 					n->relation = $3;
@@ -5200,7 +5202,7 @@ opt_nowait:	NOWAIT							{ $$ = TRUE; }
  *
  *****************************************************************************/
 
-UpdateStmt: UPDATE relation_expr
+UpdateStmt: UPDATE relation_expr_opt_alias
 			SET update_target_list
 			from_clause
 			where_clause
@@ -5878,6 +5880,20 @@ relation_expr:
 		;
 
 
+relation_expr_opt_alias: relation_expr
+				{
+					$$ = $1;
+				}
+			| relation_expr opt_as IDENT
+				{
+					Alias *alias = makeNode(Alias);
+					alias->aliasname = $3;
+					$1->alias = alias;
+					$$ = $1;
+				}
+		;
+
+
 func_table: func_expr								{ $$ = $1; }
 		;
 

src/backend/parser/parse_clause.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/parser/parse_clause.c,v 1.144 2005/11/22 18:17:16 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/parser/parse_clause.c,v 1.145 2006/01/22 05:20:34 neilc Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -160,7 +160,7 @@ setTargetTable(ParseState *pstate, RangeVar *relation,
 	 * Now build an RTE.
 	 */
 	rte = addRangeTableEntryForRelation(pstate, pstate->p_target_relation,
-										NULL, inh, false);
+										relation->alias, inh, false);
 	pstate->p_target_rangetblentry = rte;
 
 	/* assume new rte is at end */

src/test/regress/expected/delete.out

+CREATE TABLE delete_test (
+    id SERIAL PRIMARY KEY,
+    a INT
+);
+NOTICE:  CREATE TABLE will create implicit sequence "delete_test_id_seq" for serial column "delete_test.id"
+NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "delete_test_pkey" for table "delete_test"
+INSERT INTO delete_test (a) VALUES (10);
+INSERT INTO delete_test (a) VALUES (50);
+INSERT INTO delete_test (a) VALUES (100);
+-- allow an alias to be specified for DELETE's target table
+DELETE FROM delete_test AS dt WHERE dt.a > 75;
+-- if an alias is specified, don't allow the original table name
+-- to be referenced
+BEGIN;
+SET LOCAL add_missing_from = false;
+DELETE FROM delete_test dt WHERE delete_test.a > 25;
+ERROR:  invalid reference to FROM-clause entry for table "delete_test"
+HINT:  Perhaps you meant to reference the table alias "dt".
+ROLLBACK;
+SELECT * FROM delete_test;
+ id | a  
+----+----
+  1 | 10
+  2 | 50
+(2 rows)
+
+DROP TABLE delete_test;

src/test/regress/expected/rowtypes.out

@@ -59,8 +59,11 @@ select * from quadtable;
   2 | ("(,4.4)","(5.5,6.6)")
 (2 rows)
 
+begin;
+set local add_missing_from = false;
 select f1, q.c1 from quadtable;		-- fails, q is a table reference
 ERROR:  missing FROM-clause entry for table "q"
+rollback;
 select f1, (q).c1, (qq.q).c1.i from quadtable qq;
  f1 |    c1     |  i  
 ----+-----------+-----

src/test/regress/expected/update.out

@@ -22,4 +22,29 @@ SELECT * FROM update_test;
  10 |  
 (2 rows)
 
+-- aliases for the UPDATE target table
+UPDATE update_test AS t SET b = 10 WHERE t.a = 10;
+SELECT * FROM update_test;
+ a  | b  
+----+----
+ 10 | 10
+ 10 | 10
+(2 rows)
+
+UPDATE update_test t SET b = t.b + 10 WHERE t.a = 10;
+SELECT * FROM update_test;
+ a  | b  
+----+----
+ 10 | 20
+ 10 | 20
+(2 rows)
+
+-- if an alias for the target table is specified, don't allow references
+-- to the original table name
+BEGIN;
+SET LOCAL add_missing_from = false;
+UPDATE update_test AS t SET b = update_test.b + 10 WHERE t.a = 10;
+ERROR:  invalid reference to FROM-clause entry for table "update_test"
+HINT:  Perhaps you meant to reference the table alias "t".
+ROLLBACK;
 DROP TABLE update_test;

src/test/regress/parallel_schedule

@@ -60,7 +60,7 @@ ignore: random
 # ----------
 # The fourth group of parallel test
 # ----------
-test: select_into select_distinct select_distinct_on select_implicit select_having subselect union case join aggregates transactions random portals arrays btree_index hash_index update namespace prepared_xacts
+test: select_into select_distinct select_distinct_on select_implicit select_having subselect union case join aggregates transactions random portals arrays btree_index hash_index update namespace prepared_xacts delete
 
 test: privileges
 test: misc

src/test/regress/serial_schedule

-# $PostgreSQL: pgsql/src/test/regress/serial_schedule,v 1.29 2005/11/19 17:39:45 adunstan Exp $
+# $PostgreSQL: pgsql/src/test/regress/serial_schedule,v 1.30 2006/01/22 05:20:34 neilc Exp $
 # This should probably be in an order similar to parallel_schedule.
 test: boolean
 test: char
@@ -74,6 +74,7 @@ test: arrays
 test: btree_index
 test: hash_index
 test: update
+test: delete
 test: namespace
 test: prepared_xacts
 test: privileges

src/test/regress/sql/delete.sql

+CREATE TABLE delete_test (
+    id SERIAL PRIMARY KEY,
+    a INT
+);
+
+INSERT INTO delete_test (a) VALUES (10);
+INSERT INTO delete_test (a) VALUES (50);
+INSERT INTO delete_test (a) VALUES (100);
+
+-- allow an alias to be specified for DELETE's target table
+DELETE FROM delete_test AS dt WHERE dt.a > 75;
+
+-- if an alias is specified, don't allow the original table name
+-- to be referenced
+BEGIN;
+SET LOCAL add_missing_from = false;
+DELETE FROM delete_test dt WHERE delete_test.a > 25;
+ROLLBACK;
+
+SELECT * FROM delete_test;
+
+DROP TABLE delete_test;
\ No newline at end of file

src/test/regress/sql/rowtypes.sql

@@ -35,7 +35,10 @@ insert into quadtable values (2, ((null,4.4),(5.5,6.6)));
 
 select * from quadtable;
 
+begin;
+set local add_missing_from = false;
 select f1, q.c1 from quadtable;		-- fails, q is a table reference
+rollback;
 
 select f1, (q).c1, (qq.q).c1.i from quadtable qq;
 

src/test/regress/sql/update.sql

@@ -16,4 +16,20 @@ UPDATE update_test SET a = DEFAULT, b = DEFAULT;
 
 SELECT * FROM update_test;
 
+-- aliases for the UPDATE target table
+UPDATE update_test AS t SET b = 10 WHERE t.a = 10;
+
+SELECT * FROM update_test;
+
+UPDATE update_test t SET b = t.b + 10 WHERE t.a = 10;
+
+SELECT * FROM update_test;
+
+-- if an alias for the target table is specified, don't allow references
+-- to the original table name
+BEGIN;
+SET LOCAL add_missing_from = false;
+UPDATE update_test AS t SET b = update_test.b + 10 WHERE t.a = 10;
+ROLLBACK;
+
 DROP TABLE update_test;