In PL/PgSQL, allow a block's label to be optionally specified at the

end of the block:

<<label>>
begin
    ...
end label;

Similarly for loops. This is per PL/SQL. Update the documentation and
add regression tests. Patch from Pavel Stehule, code review by Neil
Conway.

doc/src/sgml/plpgsql.sgml

 <!--
-$PostgreSQL: pgsql/doc/src/sgml/plpgsql.sgml,v 1.74 2005/06/22 01:35:02 neilc Exp $
+$PostgreSQL: pgsql/doc/src/sgml/plpgsql.sgml,v 1.75 2005/07/02 08:59:47 neilc Exp $
 -->
 
 <chapter id="plpgsql"> 
@@ -456,7 +456,7 @@ a_output := a_output || $$ if v_$$ || referrer_keys.kind || $$ like '$$
     <replaceable>declarations</replaceable> </optional>
 BEGIN
     <replaceable>statements</replaceable>
-END;
+END <optional> <replaceable>label</replaceable> </optional>;
 </synopsis>
     </para>
 
@@ -1789,18 +1789,19 @@ END IF;
      <title><literal>LOOP</></title>
 
 <synopsis>
-<optional>&lt;&lt;<replaceable>label</replaceable>&gt;&gt;</optional>
+<optional> &lt;&lt;<replaceable>label</replaceable>&gt;&gt; </optional>
 LOOP
     <replaceable>statements</replaceable>
-END LOOP;
+END LOOP <optional> <replaceable>label</replaceable> </optional>;
 </synopsis>
 
      <para>
-      <literal>LOOP</> defines an unconditional loop that is repeated indefinitely
-      until terminated by an <literal>EXIT</> or <command>RETURN</command>
-      statement.  The optional label can be used by <literal>EXIT</> statements in
-      nested loops to specify which level of nesting should be
-      terminated.
+      <literal>LOOP</> defines an unconditional loop that is repeated
+      indefinitely until terminated by an <literal>EXIT</> or
+      <command>RETURN</command> statement.  The optional
+      <replaceable>label</replaceable> can be used by <literal>EXIT</>
+      and <literal>CONTINUE</literal> statements in nested loops to
+      specify which loop the statement should be applied to.
      </para>
     </sect3>
 
@@ -1920,10 +1921,10 @@ END LOOP;
      </indexterm>
 
 <synopsis>
-<optional>&lt;&lt;<replaceable>label</replaceable>&gt;&gt;</optional>
+<optional> &lt;&lt;<replaceable>label</replaceable>&gt;&gt; </optional>
 WHILE <replaceable>expression</replaceable> LOOP
     <replaceable>statements</replaceable>
-END LOOP;
+END LOOP <optional> <replaceable>label</replaceable> </optional>;
 </synopsis>
 
        <para>
@@ -1951,10 +1952,10 @@ END LOOP;
       <title><literal>FOR</> (integer variant)</title>
 
 <synopsis>
-<optional>&lt;&lt;<replaceable>label</replaceable>&gt;&gt;</optional>
+<optional> &lt;&lt;<replaceable>label</replaceable>&gt;&gt; </optional>
 FOR <replaceable>name</replaceable> IN <optional> REVERSE </optional> <replaceable>expression</replaceable> .. <replaceable>expression</replaceable> LOOP
     <replaceable>statements</replaceable>
-END LOOP;
+END LOOP <optional> <replaceable>labal</replaceable> </optional>;
 </synopsis>
 
        <para>
@@ -1997,10 +1998,10 @@ END LOOP;
      the results of a query and manipulate that data
      accordingly. The syntax is:
 <synopsis>
-<optional>&lt;&lt;<replaceable>label</replaceable>&gt;&gt;</optional>
+<optional> &lt;&lt;<replaceable>label</replaceable>&gt;&gt; </optional>
 FOR <replaceable>record_or_row</replaceable> IN <replaceable>query</replaceable> LOOP
     <replaceable>statements</replaceable>
-END LOOP;
+END LOOP <optional> <replaceable>label</replaceable> </optional>;
 </synopsis>
      The record or row variable is successively assigned each row
      resulting from the <replaceable>query</replaceable> (which must be a
@@ -2036,10 +2037,10 @@ $$ LANGUAGE plpgsql;
      The <literal>FOR-IN-EXECUTE</> statement is another way to iterate over
      rows:
 <synopsis>
-<optional>&lt;&lt;<replaceable>label</replaceable>&gt;&gt;</optional>
+<optional> &lt;&lt;<replaceable>label</replaceable>&gt;&gt; </optional>
 FOR <replaceable>record_or_row</replaceable> IN EXECUTE <replaceable>text_expression</replaceable> LOOP 
     <replaceable>statements</replaceable>
-END LOOP;
+END LOOP <optional> <replaceable>label</replaceable> </optional>;
 </synopsis>
      This is like the previous form, except that the source
      <command>SELECT</command> statement is specified as a string

src/pl/plpgsql/src/gram.y

@@ -4,7 +4,7 @@
  *						  procedural language
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/pl/plpgsql/src/gram.y,v 1.78 2005/07/01 17:40:29 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/pl/plpgsql/src/gram.y,v 1.79 2005/07/02 08:59:47 neilc Exp $
  *
  *	  This software is copyrighted by Jan Wieck - Hamburg.
  *
@@ -56,6 +56,8 @@ static	PLpgSQL_row		*read_into_scalar_list(const char *initial_name,
 											   PLpgSQL_datum *initial_datum);
 static	void			 check_sql_expr(const char *stmt);
 static	void			 plpgsql_sql_error_callback(void *arg);
+static	void			 check_labels(const char *start_label,
+									  const char *end_label);
 
 %}
 
@@ -81,6 +83,11 @@ static	void			 plpgsql_sql_error_callback(void *arg);
 			int  n_initvars;
 			int  *initvarnos;
 		}						declhdr;
+		struct
+		{
+			char *end_label;
+			List *stmts;
+		}						loop_body;
 		List					*list;
 		PLpgSQL_type			*dtype;
 		PLpgSQL_datum			*scalar;	/* a VAR, RECFIELD, or TRIGARG */
@@ -119,11 +126,11 @@ static	void			 plpgsql_sql_error_callback(void *arg);
 %type <forvariable>	for_variable
 %type <stmt>	for_control
 
-%type <str>		opt_lblname opt_label
-%type <str>		opt_exitlabel
+%type <str>		opt_lblname opt_block_label opt_label
 %type <str>		execsql_start
 
-%type <list>	proc_sect proc_stmts stmt_else loop_body
+%type <list>	proc_sect proc_stmts stmt_else
+%type <loop_body>	loop_body
 %type <stmt>	proc_stmt pl_block
 %type <stmt>	stmt_assign stmt_if stmt_loop stmt_while stmt_exit
 %type <stmt>	stmt_return stmt_return_next stmt_raise stmt_execsql
@@ -248,7 +255,7 @@ opt_semi		:
 				| ';'
 				;
 
-pl_block		: decl_sect K_BEGIN lno proc_sect exception_sect K_END
+pl_block		: decl_sect K_BEGIN lno proc_sect exception_sect K_END opt_label
 					{
 						PLpgSQL_stmt_block *new;
 
@@ -262,6 +269,7 @@ pl_block		: decl_sect K_BEGIN lno proc_sect exception_sect K_END
 						new->body		= $4;
 						new->exceptions	= $5;
 
+						check_labels($1.label, $7);
 						plpgsql_ns_pop();
 
 						$$ = (PLpgSQL_stmt *)new;
@@ -269,7 +277,7 @@ pl_block		: decl_sect K_BEGIN lno proc_sect exception_sect K_END
 				;
 
 
-decl_sect		: opt_label
+decl_sect		: opt_block_label
 					{
 						plpgsql_ns_setlocal(false);
 						$$.label	  = $1;
@@ -277,7 +285,7 @@ decl_sect		: opt_label
 						$$.initvarnos = NULL;
 						plpgsql_add_initdatums(NULL);
 					}
-				| opt_label decl_start
+				| opt_block_label decl_start
 					{
 						plpgsql_ns_setlocal(false);
 						$$.label	  = $1;
@@ -285,7 +293,7 @@ decl_sect		: opt_label
 						$$.initvarnos = NULL;
 						plpgsql_add_initdatums(NULL);
 					}
-				| opt_label decl_start decl_stmts
+				| opt_block_label decl_start decl_stmts
 					{
 						plpgsql_ns_setlocal(false);
 						if ($3 != NULL)
@@ -780,7 +788,7 @@ stmt_else		:
 					}
 				;
 
-stmt_loop		: opt_label K_LOOP lno loop_body
+stmt_loop		: opt_block_label K_LOOP lno loop_body
 					{
 						PLpgSQL_stmt_loop *new;
 
@@ -788,15 +796,16 @@ stmt_loop		: opt_label K_LOOP lno loop_body
 						new->cmd_type = PLPGSQL_STMT_LOOP;
 						new->lineno   = $3;
 						new->label	  = $1;
-						new->body	  = $4;
+						new->body	  = $4.stmts;
 
+						check_labels($1, $4.end_label);
 						plpgsql_ns_pop();
 
 						$$ = (PLpgSQL_stmt *)new;
 					}
 				;
 
-stmt_while		: opt_label K_WHILE lno expr_until_loop loop_body
+stmt_while		: opt_block_label K_WHILE lno expr_until_loop loop_body
 					{
 						PLpgSQL_stmt_while *new;
 
@@ -805,15 +814,16 @@ stmt_while		: opt_label K_WHILE lno expr_until_loop loop_body
 						new->lineno   = $3;
 						new->label	  = $1;
 						new->cond	  = $4;
-						new->body	  = $5;
+						new->body	  = $5.stmts;
 
+						check_labels($1, $5.end_label);
 						plpgsql_ns_pop();
 
 						$$ = (PLpgSQL_stmt *)new;
 					}
 				;
 
-stmt_for		: opt_label K_FOR for_control loop_body
+stmt_for		: opt_block_label K_FOR for_control loop_body
 					{
 						/* This runs after we've scanned the loop body */
 						if ($3->cmd_type == PLPGSQL_STMT_FORI)
@@ -822,7 +832,7 @@ stmt_for		: opt_label K_FOR for_control loop_body
 
 							new = (PLpgSQL_stmt_fori *) $3;
 							new->label	  = $1;
-							new->body	  = $4;
+							new->body	  = $4.stmts;
 							$$ = (PLpgSQL_stmt *) new;
 						}
 						else if ($3->cmd_type == PLPGSQL_STMT_FORS)
@@ -831,7 +841,7 @@ stmt_for		: opt_label K_FOR for_control loop_body
 
 							new = (PLpgSQL_stmt_fors *) $3;
 							new->label	  = $1;
-							new->body	  = $4;
+							new->body	  = $4.stmts;
 							$$ = (PLpgSQL_stmt *) new;
 						}
 						else
@@ -841,10 +851,11 @@ stmt_for		: opt_label K_FOR for_control loop_body
 							Assert($3->cmd_type == PLPGSQL_STMT_DYNFORS);
 							new = (PLpgSQL_stmt_dynfors *) $3;
 							new->label	  = $1;
-							new->body	  = $4;
+							new->body	  = $4.stmts;
 							$$ = (PLpgSQL_stmt *) new;
 						}
 
+						check_labels($1, $4.end_label);
 						/* close namespace started in opt_label */
 						plpgsql_ns_pop();
 					}
@@ -1037,7 +1048,7 @@ stmt_select		: K_SELECT lno
 					}
 				;
 
-stmt_exit		: exit_type lno opt_exitlabel opt_exitcond
+stmt_exit		: exit_type lno opt_label opt_exitcond
 					{
 						PLpgSQL_stmt_exit *new;
 
@@ -1245,8 +1256,11 @@ raise_level		: K_EXCEPTION
 					}
 				;
 
-loop_body		: proc_sect K_END K_LOOP ';'
-					{ $$ = $1; }
+loop_body		: proc_sect K_END K_LOOP opt_label ';'
+					{
+						$$.stmts = $1;
+						$$.end_label = $4;
+					}
 				;
 
 stmt_execsql	: execsql_start lno
@@ -1596,7 +1610,7 @@ expr_until_loop :
 					{ $$ = plpgsql_read_expression(K_LOOP, "LOOP"); }
 				;
 
-opt_label		:
+opt_block_label	:
 					{
 						plpgsql_ns_push(NULL);
 						$$ = NULL;
@@ -1608,14 +1622,15 @@ opt_label		:
 					}
 				;
 
-opt_exitlabel	:
-					{ $$ = NULL; }
+opt_label	:
+					{
+						$$ = NULL;
+					}
 				| T_LABEL
 					{
-						char	*name;
-
-						plpgsql_convert_ident(yytext, &name, 1);
-						$$ = name;
+						char *label_name;
+						plpgsql_convert_ident(yytext, &label_name, 1);
+						$$ = label_name;
 					}
 				| T_WORD
 					{
@@ -2210,4 +2225,29 @@ plpgsql_sql_error_callback(void *arg)
 	errposition(0);
 }
 
+static void
+check_labels(const char *start_label, const char *end_label)
+{
+	if (end_label)
+	{
+		if (!start_label)
+		{
+			plpgsql_error_lineno = plpgsql_scanner_lineno();
+			ereport(ERROR,
+					(errcode(ERRCODE_SYNTAX_ERROR),
+					 errmsg("end label \"%s\" specified for unlabelled block",
+							end_label)));
+		}
+
+		if (strcmp(start_label, end_label) != 0)
+		{
+			plpgsql_error_lineno = plpgsql_scanner_lineno();
+			ereport(ERROR,
+					(errcode(ERRCODE_SYNTAX_ERROR),
+					 errmsg("end label \"%s\" differs from block's label \"%s\"",
+							end_label, start_label)));
+		}
+	}
+}
+
 #include "pl_scan.c"

src/test/regress/expected/plpgsql.out

@@ -2666,3 +2666,58 @@ drop function continue_test1();
 drop function continue_test2();
 drop function continue_test3();
 drop table conttesttbl;
+-- verbose end block and end loop
+create function end_label1() returns void as $$
+<<blbl>>
+begin
+  <<flbl1>>
+  for _i in 1 .. 10 loop
+    exit flbl1;
+  end loop flbl1;
+  <<flbl2>>
+  for _i in 1 .. 10 loop
+    exit flbl2;
+  end loop;
+end blbl;
+$$ language plpgsql;
+select end_label1();
+ end_label1 
+------------
+ 
+(1 row)
+
+drop function end_label1();
+-- should fail: undefined end label
+create function end_label2() returns void as $$
+begin
+  for _i in 1 .. 10 loop
+    exit;
+  end loop flbl1;
+end;
+$$ language plpgsql;
+ERROR:  no such label at or near "flbl1" at character 101
+LINE 5:   end loop flbl1;
+                   ^
+-- should fail: end label does not match start label
+create function end_label3() returns void as $$
+<<outer_label>>
+begin
+  <<inner_label>>
+  for _i in 1 .. 10 loop
+    exit;
+  end loop outer_label;
+end;
+$$ language plpgsql;
+ERROR:  end label "outer_label" differs from block's label "inner_label"
+CONTEXT:  compile of PL/pgSQL function "end_label3" near line 6
+-- should fail: end label on a block without a start label
+create function end_label4() returns void as $$
+<<outer_label>>
+begin
+  for _i in 1 .. 10 loop
+    exit;
+  end loop outer_label;
+end;
+$$ language plpgsql;
+ERROR:  end label "outer_label" specified for unlabelled block
+CONTEXT:  compile of PL/pgSQL function "end_label4" near line 5

src/test/regress/sql/plpgsql.sql

@@ -2232,3 +2232,51 @@ drop function continue_test1();
 drop function continue_test2();
 drop function continue_test3();
 drop table conttesttbl;
+
+-- verbose end block and end loop
+create function end_label1() returns void as $$
+<<blbl>>
+begin
+  <<flbl1>>
+  for _i in 1 .. 10 loop
+    exit flbl1;
+  end loop flbl1;
+  <<flbl2>>
+  for _i in 1 .. 10 loop
+    exit flbl2;
+  end loop;
+end blbl;
+$$ language plpgsql;
+
+select end_label1();
+drop function end_label1();
+
+-- should fail: undefined end label
+create function end_label2() returns void as $$
+begin
+  for _i in 1 .. 10 loop
+    exit;
+  end loop flbl1;
+end;
+$$ language plpgsql;
+
+-- should fail: end label does not match start label
+create function end_label3() returns void as $$
+<<outer_label>>
+begin
+  <<inner_label>>
+  for _i in 1 .. 10 loop
+    exit;
+  end loop outer_label;
+end;
+$$ language plpgsql;
+
+-- should fail: end label on a block without a start label
+create function end_label4() returns void as $$
+<<outer_label>>
+begin
+  for _i in 1 .. 10 loop
+    exit;
+  end loop outer_label;
+end;
+$$ language plpgsql;