Modify the handling of RAISE without parameters so that the error it throws

can be caught in the same places that could catch an ordinary RAISE ERROR
in the same location.  The previous coding insisted on throwing the error
from the block containing the active exception handler; which is arguably
more surprising, and definitely unlike Oracle's behavior.

Not back-patching, since this is a pretty obscure corner case.  The risk
of breaking somebody's code in a minor version update seems to outweigh
any possible benefit.

Piyush Newe, reviewed by David Fetter

doc/src/sgml/plpgsql.sgml

-<!-- $PostgreSQL: pgsql/doc/src/sgml/plpgsql.sgml,v 1.156 2010/07/29 19:34:40 petere Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/plpgsql.sgml,v 1.157 2010/08/09 02:25:05 tgl Exp $ -->
 
 <chapter id="plpgsql">
   <title><application>PL/pgSQL</application> - <acronym>SQL</acronym> Procedural Language</title>
@@ -3012,10 +3012,21 @@ RAISE unique_violation USING MESSAGE = 'Duplicate user ID: ' || user_id;
     The last variant of <command>RAISE</> has no parameters at all.
     This form can only be used inside a <literal>BEGIN</> block's
     <literal>EXCEPTION</> clause;
-    it causes the error currently being handled to be re-thrown to the
-    next enclosing block.
+    it causes the error currently being handled to be re-thrown.
    </para>
 
+   <note>
+    <para>
+     Before <productname>PostgreSQL</> 9.1, <command>RAISE</> without
+     parameters was interpreted as re-throwing the error from the block
+     containing the active exception handler.  Thus an <literal>EXCEPTION</>
+     clause nested within that handler could not catch it, even if the
+     <command>RAISE</> was within the nested <literal>EXCEPTION</> clause's
+     block. This was deemed surprising as well as being incompatible with
+     Oracle's PL/SQL.
+    </para>
+   </note>
+
    <para>
     If no condition name nor SQLSTATE is specified in a
     <command>RAISE EXCEPTION</command> command, the default is to use

src/pl/plpgsql/src/pl_exec.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/pl/plpgsql/src/pl_exec.c,v 1.261 2010/07/06 19:19:01 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/pl/plpgsql/src/pl_exec.c,v 1.262 2010/08/09 02:25:05 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -327,10 +327,6 @@ plpgsql_exec_function(PLpgSQL_function *func, FunctionCallInfo fcinfo)
 			ereport(ERROR,
 					(errcode(ERRCODE_SYNTAX_ERROR),
 					 errmsg("CONTINUE cannot be used outside a loop")));
-		else if (rc == PLPGSQL_RC_RERAISE)
-			ereport(ERROR,
-					(errcode(ERRCODE_SYNTAX_ERROR),
-					 errmsg("RAISE without parameters cannot be used outside an exception handler")));
 		else
 			ereport(ERROR,
 			   (errcode(ERRCODE_S_R_E_FUNCTION_EXECUTED_NO_RETURN_STATEMENT),
@@ -695,10 +691,6 @@ plpgsql_exec_trigger(PLpgSQL_function *func,
 			ereport(ERROR,
 					(errcode(ERRCODE_SYNTAX_ERROR),
 					 errmsg("CONTINUE cannot be used outside a loop")));
-		else if (rc == PLPGSQL_RC_RERAISE)
-			ereport(ERROR,
-					(errcode(ERRCODE_SYNTAX_ERROR),
-					 errmsg("RAISE without parameters cannot be used outside an exception handler")));
 		else
 			ereport(ERROR,
 			   (errcode(ERRCODE_S_R_E_FUNCTION_EXECUTED_NO_RETURN_STATEMENT),
@@ -1019,6 +1011,7 @@ exec_stmt_block(PLpgSQL_execstate *estate, PLpgSQL_stmt_block *block)
 		MemoryContext oldcontext = CurrentMemoryContext;
 		ResourceOwner oldowner = CurrentResourceOwner;
 		ExprContext *old_eval_econtext = estate->eval_econtext;
+		ErrorData *save_cur_error = estate->cur_error;
 
 		estate->err_text = gettext_noop("during statement block entry");
 
@@ -1130,6 +1123,12 @@ exec_stmt_block(PLpgSQL_execstate *estate, PLpgSQL_stmt_block *block)
 									unpack_sql_state(edata->sqlerrcode));
 					assign_text_var(errm_var, edata->message);
 
+					/*
+					 * Also set up cur_error so the error data is accessible
+					 * inside the handler.
+					 */
+					estate->cur_error = edata;
+
 					estate->err_text = NULL;
 
 					rc = exec_stmts(estate, exception->action);
@@ -1141,14 +1140,17 @@ exec_stmt_block(PLpgSQL_execstate *estate, PLpgSQL_stmt_block *block)
 					errm_var->value = (Datum) 0;
 					errm_var->isnull = true;
 
-					/* re-throw error if requested by handler */
-					if (rc == PLPGSQL_RC_RERAISE)
-						ReThrowError(edata);
-
 					break;
 				}
 			}
 
+			/*
+			 * Restore previous state of cur_error, whether or not we executed
+			 * a handler.  This is needed in case an error got thrown from
+			 * some inner block's exception handler.
+			 */
+			estate->cur_error = save_cur_error;
+
 			/* If no match found, re-throw the error */
 			if (e == NULL)
 				ReThrowError(edata);
@@ -1156,6 +1158,8 @@ exec_stmt_block(PLpgSQL_execstate *estate, PLpgSQL_stmt_block *block)
 				FreeErrorData(edata);
 		}
 		PG_END_TRY();
+
+		Assert(save_cur_error == estate->cur_error);
 	}
 	else
 	{
@@ -1177,7 +1181,6 @@ exec_stmt_block(PLpgSQL_execstate *estate, PLpgSQL_stmt_block *block)
 		case PLPGSQL_RC_OK:
 		case PLPGSQL_RC_RETURN:
 		case PLPGSQL_RC_CONTINUE:
-		case PLPGSQL_RC_RERAISE:
 			return rc;
 
 		case PLPGSQL_RC_EXIT:
@@ -1599,7 +1602,6 @@ exec_stmt_loop(PLpgSQL_execstate *estate, PLpgSQL_stmt_loop *stmt)
 				break;
 
 			case PLPGSQL_RC_RETURN:
-			case PLPGSQL_RC_RERAISE:
 				return rc;
 
 			default:
@@ -1663,7 +1665,6 @@ exec_stmt_while(PLpgSQL_execstate *estate, PLpgSQL_stmt_while *stmt)
 				break;
 
 			case PLPGSQL_RC_RETURN:
-			case PLPGSQL_RC_RERAISE:
 				return rc;
 
 			default:
@@ -1782,8 +1783,7 @@ exec_stmt_fori(PLpgSQL_execstate *estate, PLpgSQL_stmt_fori *stmt)
 		 */
 		rc = exec_stmts(estate, stmt->body);
 
-		if (rc == PLPGSQL_RC_RETURN ||
-			rc == PLPGSQL_RC_RERAISE)
+		if (rc == PLPGSQL_RC_RETURN)
 			break;				/* break out of the loop */
 		else if (rc == PLPGSQL_RC_EXIT)
 		{
@@ -2437,7 +2437,14 @@ exec_stmt_raise(PLpgSQL_execstate *estate, PLpgSQL_stmt_raise *stmt)
 	/* RAISE with no parameters: re-throw current exception */
 	if (stmt->condname == NULL && stmt->message == NULL &&
 		stmt->options == NIL)
-		return PLPGSQL_RC_RERAISE;
+	{
+		if (estate->cur_error != NULL)
+			ReThrowError(estate->cur_error);
+		/* oops, we're not inside a handler */
+		ereport(ERROR,
+				(errcode(ERRCODE_SYNTAX_ERROR),
+				 errmsg("RAISE without parameters cannot be used outside an exception handler")));
+	}
 
 	if (stmt->condname)
 	{
@@ -2637,6 +2644,7 @@ plpgsql_estate_setup(PLpgSQL_execstate *estate,
 
 	estate->rettupdesc = NULL;
 	estate->exitlabel = NULL;
+	estate->cur_error = NULL;
 
 	estate->tuple_store = NULL;
 	if (rsi)

src/pl/plpgsql/src/plpgsql.h

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/pl/plpgsql/src/plpgsql.h,v 1.130 2010/02/26 02:01:35 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/pl/plpgsql/src/plpgsql.h,v 1.131 2010/08/09 02:25:05 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -115,8 +115,7 @@ enum
 	PLPGSQL_RC_OK,
 	PLPGSQL_RC_EXIT,
 	PLPGSQL_RC_RETURN,
-	PLPGSQL_RC_CONTINUE,
-	PLPGSQL_RC_RERAISE
+	PLPGSQL_RC_CONTINUE
 };
 
 /* ----------
@@ -699,6 +698,7 @@ typedef struct PLpgSQL_execstate
 	TupleDesc	rettupdesc;
 	char	   *exitlabel;		/* the "target" label of the current EXIT or
 								 * CONTINUE stmt, if any */
+	ErrorData  *cur_error;		/* current exception handler's error */
 
 	Tuplestorestate *tuple_store;		/* SRFs accumulate results here */
 	MemoryContext tuple_store_cxt;

src/test/regress/expected/plpgsql.out

@@ -2312,6 +2312,35 @@ $$ language plpgsql;
 select raise_test2(10);
 ERROR:  too few parameters specified for RAISE
 CONTEXT:  PL/pgSQL function "raise_test2" line 3 at RAISE
+-- Test re-RAISE inside a nested exception block.  This case is allowed
+-- by Oracle's PL/SQL but was handled differently by PG before 9.1.
+CREATE FUNCTION reraise_test() RETURNS void AS $$
+BEGIN
+   BEGIN
+       RAISE syntax_error;
+   EXCEPTION
+       WHEN syntax_error THEN
+           BEGIN
+               raise notice 'exception % thrown in inner block, reraising', sqlerrm;
+               RAISE;
+           EXCEPTION
+               WHEN OTHERS THEN
+                   raise notice 'RIGHT - exception % caught in inner block', sqlerrm;
+           END;
+   END;
+EXCEPTION
+   WHEN OTHERS THEN
+       raise notice 'WRONG - exception % caught in outer block', sqlerrm;
+END;
+$$ LANGUAGE plpgsql;
+SELECT reraise_test();
+NOTICE:  exception syntax_error thrown in inner block, reraising
+NOTICE:  RIGHT - exception syntax_error caught in inner block
+ reraise_test 
+--------------
+ 
+(1 row)
+
 --
 -- reject function definitions that contain malformed SQL queries at
 -- compile-time, where possible
@@ -3577,7 +3606,7 @@ end;
 $$ language plpgsql;
 select raise_test();
 ERROR:  RAISE without parameters cannot be used outside an exception handler
-CONTEXT:  PL/pgSQL function "raise_test"
+CONTEXT:  PL/pgSQL function "raise_test" line 3 at RAISE
 -- check cases where implicit SQLSTATE variable could be confused with
 -- SQLSTATE as a keyword, cf bug #5524
 create or replace function raise_test() returns void as $$

src/test/regress/sql/plpgsql.sql

@@ -1966,6 +1966,31 @@ $$ language plpgsql;
 
 select raise_test2(10);
 
+-- Test re-RAISE inside a nested exception block.  This case is allowed
+-- by Oracle's PL/SQL but was handled differently by PG before 9.1.
+
+CREATE FUNCTION reraise_test() RETURNS void AS $$
+BEGIN
+   BEGIN
+       RAISE syntax_error;
+   EXCEPTION
+       WHEN syntax_error THEN
+           BEGIN
+               raise notice 'exception % thrown in inner block, reraising', sqlerrm;
+               RAISE;
+           EXCEPTION
+               WHEN OTHERS THEN
+                   raise notice 'RIGHT - exception % caught in inner block', sqlerrm;
+           END;
+   END;
+EXCEPTION
+   WHEN OTHERS THEN
+       raise notice 'WRONG - exception % caught in outer block', sqlerrm;
+END;
+$$ LANGUAGE plpgsql;
+
+SELECT reraise_test();
+
 --
 -- reject function definitions that contain malformed SQL queries at
 -- compile-time, where possible