Add a CONTINUE statement to PL/PgSQL, which can be used to begin the

next iteration of a loop. Update documentation and add regression tests.
Patch from Pavel Stehule, reviewed by Neil Conway.

doc/src/sgml/plpgsql.sgml

 <!--
-$PostgreSQL: pgsql/doc/src/sgml/plpgsql.sgml,v 1.73 2005/06/19 23:39:05 neilc Exp $
+$PostgreSQL: pgsql/doc/src/sgml/plpgsql.sgml,v 1.74 2005/06/22 01:35:02 neilc Exp $
 -->
 
 <chapter id="plpgsql"> 
@@ -1779,10 +1779,10 @@ END IF;
     </indexterm>
 
     <para>
-     With the <literal>LOOP</>, <literal>EXIT</>, <literal>WHILE</>,
-     and <literal>FOR</> statements, you can arrange for your
-     <application>PL/pgSQL</application> function to repeat a series
-     of commands.
+     With the <literal>LOOP</>, <literal>EXIT</>,
+     <literal>CONTINUE</>, <literal>WHILE</>, and <literal>FOR</>
+     statements, you can arrange for your <application>PL/pgSQL</>
+     function to repeat a series of commands.
     </para>
 
     <sect3>
@@ -1807,30 +1807,36 @@ END LOOP;
      <sect3>
       <title><literal>EXIT</></title>
 
+     <indexterm>
+      <primary>EXIT</primary>
+      <secondary>in PL/pgSQL</secondary>
+     </indexterm>
+
 <synopsis>
 EXIT <optional> <replaceable>label</replaceable> </optional> <optional> WHEN <replaceable>expression</replaceable> </optional>;
 </synopsis>
 
        <para>
-        If no <replaceable>label</replaceable> is given,
-        the innermost loop is terminated and the
-        statement following <literal>END LOOP</> is executed next.
-        If <replaceable>label</replaceable> is given, it
-        must be the label of the current or some outer level of nested loop
-        or block. Then the named loop or block is terminated and control
-        continues with the statement after the loop's/block's corresponding
-        <literal>END</>.
+        If no <replaceable>label</replaceable> is given, the innermost
+        loop is terminated and the statement following <literal>END
+        LOOP</> is executed next.  If <replaceable>label</replaceable>
+        is given, it must be the label of the current or some outer
+        level of nested loop or block. Then the named loop or block is
+        terminated and control continues with the statement after the
+        loop's/block's corresponding <literal>END</>.
        </para>
 
        <para>
-        If <literal>WHEN</> is present, loop exit occurs only if the specified
-        condition is true, otherwise control passes to the statement after
-        <literal>EXIT</>.
+        If <literal>WHEN</> is specified, the loop exit occurs only if
+        <replaceable>expression</> is true. Otherwise, control passes
+        to the statement after <literal>EXIT</>.
        </para>
 
        <para>
-        <literal>EXIT</> can be used to cause early exit from all types of
-        loops; it is not limited to use with unconditional loops.
+        <literal>EXIT</> can be used with all types of loops; it is
+        not limited to use with unconditional loops. When used with a
+        <literal>BEGIN</literal> block, <literal>EXIT</literal> passes
+        control to the next statement after the end of the block.
        </para>
 
        <para>
@@ -1858,9 +1864,61 @@ END;
        </para>
      </sect3>
 
+     <sect3>
+      <title><literal>CONTINUE</></title>
+
+     <indexterm>
+      <primary>CONTINUE</primary>
+      <secondary>in PL/pgSQL</secondary>
+     </indexterm>
+
+<synopsis>
+CONTINUE <optional> <replaceable>label</replaceable> </optional> <optional> WHEN <replaceable>expression</replaceable> </optional>;
+</synopsis>
+
+       <para>
+        If no <replaceable>label</> is given, the next iteration of
+        the innermost loop is begun. That is, control is passed back
+        to the loop control expression (if any), and the body of the
+        loop is re-evaluated. If <replaceable>label</> is present, it
+        specifies the label of the loop whose execution will be
+        continued.
+       </para>
+
+       <para>
+        If <literal>WHEN</> is specified, the next iteration of the
+        loop is begun only if <replaceable>expression</> is
+        true. Otherwise, control passes to the statement after
+        <literal>CONTINUE</>.
+       </para>
+
+       <para>
+        <literal>CONTINUE</> can be used with all types of loops; it
+        is not limited to use with unconditional loops.
+       </para>
+
+       <para>
+        Examples:
+<programlisting>
+LOOP
+    -- some computations
+    EXIT WHEN count &gt; 100;
+    CONTINUE WHEN count &lt; 50;
+    -- some computations for count IN [50 .. 100] 
+END LOOP;
+</programlisting>
+       </para>
+     </sect3>
+
+
      <sect3>
       <title><literal>WHILE</></title>
 
+     <indexterm>
+      <primary>WHILE</primary>
+      <secondary>in PL/pgSQL</secondary>
+     </indexterm>
+
 <synopsis>
 <optional>&lt;&lt;<replaceable>label</replaceable>&gt;&gt;</optional>
 WHILE <replaceable>expression</replaceable> LOOP

src/pl/plpgsql/src/gram.y

@@ -4,7 +4,7 @@
  *						  procedural language
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/pl/plpgsql/src/gram.y,v 1.76 2005/06/14 06:43:14 neilc Exp $
+ *	  $PostgreSQL: pgsql/src/pl/plpgsql/src/gram.y,v 1.77 2005/06/22 01:35:02 neilc Exp $
  *
  *	  This software is copyrighted by Jan Wieck - Hamburg.
  *
@@ -61,6 +61,7 @@ static	void			 plpgsql_sql_error_callback(void *arg);
 
 %union {
 		int32					ival;
+		bool					boolean;
 		char					*str;
 		struct
 		{
@@ -100,7 +101,7 @@ static	void			 plpgsql_sql_error_callback(void *arg);
 %type <declhdr> decl_sect
 %type <varname> decl_varname
 %type <str>		decl_renname
-%type <ival>	decl_const decl_notnull
+%type <boolean>	decl_const decl_notnull exit_type
 %type <expr>	decl_defval decl_cursor_query
 %type <dtype>	decl_datatype
 %type <row>		decl_cursor_args
@@ -153,6 +154,7 @@ static	void			 plpgsql_sql_error_callback(void *arg);
 %token	K_BEGIN
 %token	K_CLOSE
 %token	K_CONSTANT
+%token	K_CONTINUE
 %token	K_CURSOR
 %token	K_DEBUG
 %token	K_DECLARE
@@ -514,9 +516,9 @@ decl_renname	: T_WORD
 				;
 
 decl_const		:
-					{ $$ = 0; }
+					{ $$ = false; }
 				| K_CONSTANT
-					{ $$ = 1; }
+					{ $$ = true; }
 				;
 
 decl_datatype	:
@@ -531,9 +533,9 @@ decl_datatype	:
 				;
 
 decl_notnull	:
-					{ $$ = 0; }
+					{ $$ = false; }
 				| K_NOT K_NULL
-					{ $$ = 1; }
+					{ $$ = true; }
 				;
 
 decl_defval		: ';'
@@ -1035,13 +1037,14 @@ stmt_select		: K_SELECT lno
 					}
 				;
 
-stmt_exit		: K_EXIT lno opt_exitlabel opt_exitcond
+stmt_exit		: exit_type lno opt_exitlabel opt_exitcond
 					{
 						PLpgSQL_stmt_exit *new;
 
 						new = palloc0(sizeof(PLpgSQL_stmt_exit));
 						new->cmd_type = PLPGSQL_STMT_EXIT;
-						new->lineno   = $2;
+						new->is_exit  = $1;
+						new->lineno	  = $2;
 						new->label	  = $3;
 						new->cond	  = $4;
 
@@ -1049,6 +1052,16 @@ stmt_exit		: K_EXIT lno opt_exitlabel opt_exitcond
 					}
 				;
 
+exit_type		: K_EXIT
+					{
+						$$ = true;
+					}
+				| K_CONTINUE
+					{
+						$$ = false;
+					}
+				;
+
 stmt_return		: K_RETURN lno
 					{
 						PLpgSQL_stmt_return *new;
@@ -1056,8 +1069,8 @@ stmt_return		: K_RETURN lno
 						new = palloc0(sizeof(PLpgSQL_stmt_return));
 						new->cmd_type = PLPGSQL_STMT_RETURN;
 						new->lineno   = $2;
-						new->expr = NULL;
-						new->retvarno	= -1;
+						new->expr	  = NULL;
+						new->retvarno = -1;
 
 						if (plpgsql_curr_compile->fn_retset)
 						{

src/pl/plpgsql/src/pl_funcs.c

@@ -3,7 +3,7 @@
  *			  procedural language
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/pl/plpgsql/src/pl_funcs.c,v 1.44 2005/06/19 01:06:12 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/pl/plpgsql/src/pl_funcs.c,v 1.45 2005/06/22 01:35:02 neilc Exp $
  *
  *	  This software is copyrighted by Jan Wieck - Hamburg.
  *
@@ -845,7 +845,8 @@ static void
 dump_exit(PLpgSQL_stmt_exit *stmt)
 {
 	dump_ind();
-	printf("EXIT lbl='%s'", stmt->label);
+	printf("%s label='%s'",
+		   stmt->is_exit ? "EXIT" : "CONTINUE", stmt->label);
 	if (stmt->cond != NULL)
 	{
 		printf(" WHEN ");

src/pl/plpgsql/src/plpgsql.h

@@ -3,7 +3,7 @@
  *			  procedural language
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/pl/plpgsql/src/plpgsql.h,v 1.63 2005/06/14 06:43:14 neilc Exp $
+ *	  $PostgreSQL: pgsql/src/pl/plpgsql/src/plpgsql.h,v 1.64 2005/06/22 01:35:02 neilc Exp $
  *
  *	  This software is copyrighted by Jan Wieck - Hamburg.
  *
@@ -125,7 +125,8 @@ enum
 {
 	PLPGSQL_RC_OK,
 	PLPGSQL_RC_EXIT,
-	PLPGSQL_RC_RETURN
+	PLPGSQL_RC_RETURN,
+	PLPGSQL_RC_CONTINUE
 };
 
 /* ----------
@@ -485,9 +486,10 @@ typedef struct
 
 
 typedef struct
-{								/* EXIT statement			*/
+{								/* EXIT or CONTINUE statement			*/
 	int			cmd_type;
 	int			lineno;
+	bool		is_exit;		/* Is this an exit or a continue? */
 	char	   *label;
 	PLpgSQL_expr *cond;
 } PLpgSQL_stmt_exit;
@@ -610,7 +612,8 @@ typedef struct
 	bool		readonly_func;
 
 	TupleDesc	rettupdesc;
-	char	   *exitlabel;
+	char	   *exitlabel;		/* the "target" label of the current
+								 * EXIT or CONTINUE stmt, if any */
 
 	Tuplestorestate *tuple_store;		/* SRFs accumulate results here */
 	MemoryContext tuple_store_cxt;

src/pl/plpgsql/src/scan.l

@@ -4,7 +4,7 @@
  *			  procedural language
  *
  * IDENTIFICATION
- *    $PostgreSQL: pgsql/src/pl/plpgsql/src/scan.l,v 1.40 2005/03/11 19:13:43 momjian Exp $
+ *    $PostgreSQL: pgsql/src/pl/plpgsql/src/scan.l,v 1.41 2005/06/22 01:35:02 neilc Exp $
  *
  *    This software is copyrighted by Jan Wieck - Hamburg.
  *
@@ -139,6 +139,7 @@ alias			{ return K_ALIAS;			}
 begin			{ return K_BEGIN;			}
 close			{ return K_CLOSE;			}
 constant		{ return K_CONSTANT;		}
+continue		{ return K_CONTINUE;		}
 cursor			{ return K_CURSOR;			}
 debug			{ return K_DEBUG;			}
 declare			{ return K_DECLARE;			}

src/test/regress/expected/plpgsql.out

@@ -2491,3 +2491,140 @@ NOTICE:  {10,20,30}; 20; xyz; xyzabc; (10,aaa,,30); <NULL>
 (1 row)
 
 drop function raise_exprs();
+-- continue statement 
+create table conttesttbl(idx serial, v integer);
+NOTICE:  CREATE TABLE will create implicit sequence "conttesttbl_idx_seq" for serial column "conttesttbl.idx"
+insert into conttesttbl(v) values(10);
+insert into conttesttbl(v) values(20);
+insert into conttesttbl(v) values(30);
+insert into conttesttbl(v) values(40);
+create function continue_test1() returns void as $$
+declare _i integer = 0; _r record;
+begin
+  raise notice '---1---';
+  loop
+    _i := _i + 1;
+    raise notice '%', _i;
+    continue when _i < 10;
+    exit;
+  end loop;
+
+  raise notice '---2---';
+  <<lbl>>
+  loop
+    _i := _i - 1;
+    loop
+      raise notice '%', _i;
+      continue lbl when _i > 0;
+      exit lbl;
+    end loop;
+  end loop;
+
+  raise notice '---3---';
+  <<the_loop>>
+  while _i < 10 loop
+    _i := _i + 1;
+    continue the_loop when _i % 2 = 0;
+    raise notice '%', _i;
+  end loop;
+
+  raise notice '---4---';
+  for _i in 1..10 loop
+    begin
+      -- applies to outer loop, not the nested begin block
+      continue when _i < 5; 
+      raise notice '%', _i;
+    end;
+  end loop;
+
+  raise notice '---5---';
+  for _r in select * from conttesttbl loop
+    continue when _r.v <= 20;
+    raise notice '%', _r.v;
+  end loop;
+
+  raise notice '---6---';
+  for _r in execute 'select * from conttesttbl' loop
+    continue when _r.v <= 20;
+    raise notice '%', _r.v;
+  end loop;  
+end; $$ language plpgsql;
+select continue_test1();
+NOTICE:  ---1---
+NOTICE:  1
+NOTICE:  2
+NOTICE:  3
+NOTICE:  4
+NOTICE:  5
+NOTICE:  6
+NOTICE:  7
+NOTICE:  8
+NOTICE:  9
+NOTICE:  10
+NOTICE:  ---2---
+NOTICE:  9
+NOTICE:  8
+NOTICE:  7
+NOTICE:  6
+NOTICE:  5
+NOTICE:  4
+NOTICE:  3
+NOTICE:  2
+NOTICE:  1
+NOTICE:  0
+NOTICE:  ---3---
+NOTICE:  1
+NOTICE:  3
+NOTICE:  5
+NOTICE:  7
+NOTICE:  9
+NOTICE:  ---4---
+NOTICE:  5
+NOTICE:  6
+NOTICE:  7
+NOTICE:  8
+NOTICE:  9
+NOTICE:  10
+NOTICE:  ---5---
+NOTICE:  30
+NOTICE:  40
+NOTICE:  ---6---
+NOTICE:  30
+NOTICE:  40
+ continue_test1 
+----------------
+ 
+(1 row)
+
+-- CONTINUE is only legal inside a loop
+create function continue_test2() returns void as $$
+begin
+    begin
+        continue;
+    end;
+    return;
+end;
+$$ language plpgsql;
+-- should fail
+select continue_test2();
+ERROR:  CONTINUE cannot be used outside a loop
+CONTEXT:  PL/pgSQL function "continue_test2"
+-- CONTINUE can't reference the label of a named block
+create function continue_test3() returns void as $$
+begin
+    <<begin_block1>>
+    begin
+        loop
+            continue begin_block1;
+        end loop;
+    end;
+end;
+$$ language plpgsql;
+-- should fail
+select continue_test3();
+ERROR:  CONTINUE cannot be used outside a loop
+CONTEXT:  PL/pgSQL function "continue_test3"
+drop function continue_test1();
+drop function continue_test2();
+drop function continue_test3();
+drop table conttesttbl;

src/test/regress/sql/plpgsql.sql

@@ -2112,3 +2112,97 @@ end;$$ language plpgsql;
 
 select raise_exprs();
 drop function raise_exprs();
+
+-- continue statement 
+create table conttesttbl(idx serial, v integer);
+insert into conttesttbl(v) values(10);
+insert into conttesttbl(v) values(20);
+insert into conttesttbl(v) values(30);
+insert into conttesttbl(v) values(40);
+
+create function continue_test1() returns void as $$
+declare _i integer = 0; _r record;
+begin
+  raise notice '---1---';
+  loop
+    _i := _i + 1;
+    raise notice '%', _i;
+    continue when _i < 10;
+    exit;
+  end loop;
+
+  raise notice '---2---';
+  <<lbl>>
+  loop
+    _i := _i - 1;
+    loop
+      raise notice '%', _i;
+      continue lbl when _i > 0;
+      exit lbl;
+    end loop;
+  end loop;
+
+  raise notice '---3---';
+  <<the_loop>>
+  while _i < 10 loop
+    _i := _i + 1;
+    continue the_loop when _i % 2 = 0;
+    raise notice '%', _i;
+  end loop;
+
+  raise notice '---4---';
+  for _i in 1..10 loop
+    begin
+      -- applies to outer loop, not the nested begin block
+      continue when _i < 5; 
+      raise notice '%', _i;
+    end;
+  end loop;
+
+  raise notice '---5---';
+  for _r in select * from conttesttbl loop
+    continue when _r.v <= 20;
+    raise notice '%', _r.v;
+  end loop;
+
+  raise notice '---6---';
+  for _r in execute 'select * from conttesttbl' loop
+    continue when _r.v <= 20;
+    raise notice '%', _r.v;
+  end loop;  
+end; $$ language plpgsql;
+
+select continue_test1();
+
+-- CONTINUE is only legal inside a loop
+create function continue_test2() returns void as $$
+begin
+    begin
+        continue;
+    end;
+    return;
+end;
+$$ language plpgsql;
+
+-- should fail
+select continue_test2();
+
+-- CONTINUE can't reference the label of a named block
+create function continue_test3() returns void as $$
+begin
+    <<begin_block1>>
+    begin
+        loop
+            continue begin_block1;
+        end loop;
+    end;
+end;
+$$ language plpgsql;
+
+-- should fail
+select continue_test3();
+
+drop function continue_test1();
+drop function continue_test2();
+drop function continue_test3();
+drop table conttesttbl;