Cause plpgsql's PERFORM to behave according to its documentation,

which says that PERFORM will execute any SELECT query and discard the
result.  The former implementation would in fact raise an error if the
result contained more than one row or more than one column.

Also, change plpgsql's error-logging mechanism to emit the additional
messages about error location at NOTICE rather than DEBUG level.  This
allows them to be seen by the client without having to dig into the
postmaster log file (which may be nonexistent or inaccessible by the
client).

doc/src/sgml/plsql.sgml

 <!--
-$Header: /cvsroot/pgsql/doc/src/sgml/Attic/plsql.sgml,v 2.34 2001/05/28 14:58:58 petere Exp $
+$Header: /cvsroot/pgsql/doc/src/sgml/Attic/plsql.sgml,v 2.35 2001/05/28 19:33:24 tgl Exp $
 -->
 
 <chapter id="plpgsql"> 
@@ -1402,15 +1402,12 @@ RAISE EXCEPTION ''Inexistent ID --> %'',user_id;
      error, parse error). And it is possible that the database backend
      is in an inconsistent state at this point so returning to the upper
      executor or issuing more commands might corrupt the whole database.
-     And even if, at this point the information, that the transaction
-     is aborted, is already sent to the client application, so resuming
-     operation does not make any sense.
     </para>
 
     <para>
      Thus, the only thing PL/pgSQL currently does when it encounters
      an abort during execution of a function or trigger
-     procedure is to write some additional DEBUG level log messages
+     procedure is to write some additional NOTICE level log messages
      telling in which function and where (line number and type of
      statement) this happened.
     </para>

src/pl/plpgsql/src/pl_exec.c

@@ -3,7 +3,7 @@
  *			  procedural language
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/pl/plpgsql/src/pl_exec.c,v 1.43 2001/05/21 14:22:19 wieck Exp $
+ *	  $Header: /cvsroot/pgsql/src/pl/plpgsql/src/pl_exec.c,v 1.44 2001/05/28 19:33:24 tgl Exp $
  *
  *	  This software is copyrighted by Jan Wieck - Hamburg.
  *
@@ -185,7 +185,7 @@ plpgsql_exec_function(PLpgSQL_function * func, FunctionCallInfo fcinfo)
 		 */
 		if (error_info_func != NULL)
 		{
-			elog(DEBUG, "Last error occured while executing PL/pgSQL function %s",
+			elog(NOTICE, "Error occurred while executing PL/pgSQL function %s",
 				 error_info_func->fn_name);
 			if (error_info_stmt != NULL)
 			{
@@ -248,15 +248,15 @@ plpgsql_exec_function(PLpgSQL_function * func, FunctionCallInfo fcinfo)
 						stmttype = "unknown";
 						break;
 				}
-				elog(DEBUG, "line %d at %s", error_info_stmt->lineno,
+				elog(NOTICE, "line %d at %s", error_info_stmt->lineno,
 					 stmttype);
 			}
 			else
 			{
 				if (error_info_text != NULL)
-					elog(DEBUG, "%s", error_info_text);
+					elog(NOTICE, "%s", error_info_text);
 				else
-					elog(DEBUG, "no more error information available");
+					elog(NOTICE, "no more error information available");
 			}
 
 			error_info_func = NULL;
@@ -491,7 +491,7 @@ plpgsql_exec_trigger(PLpgSQL_function * func,
 		 */
 		if (error_info_func != NULL)
 		{
-			elog(DEBUG, "Last error occured while executing PL/pgSQL function %s",
+			elog(NOTICE, "Error occurred while executing PL/pgSQL function %s",
 				 error_info_func->fn_name);
 			if (error_info_stmt != NULL)
 			{
@@ -548,15 +548,15 @@ plpgsql_exec_trigger(PLpgSQL_function * func,
 						stmttype = "unknown";
 						break;
 				}
-				elog(DEBUG, "line %d at %s", error_info_stmt->lineno,
+				elog(NOTICE, "line %d at %s", error_info_stmt->lineno,
 					 stmttype);
 			}
 			else
 			{
 				if (error_info_text != NULL)
-					elog(DEBUG, "%s", error_info_text);
+					elog(NOTICE, "%s", error_info_text);
 				else
-					elog(DEBUG, "no more error information available");
+					elog(NOTICE, "no more error information available");
 			}
 
 			error_info_func = NULL;
@@ -1065,15 +1065,41 @@ exec_stmt(PLpgSQL_execstate * estate, PLpgSQL_stmt * stmt)
 /* ----------
  * exec_stmt_assign			Evaluate an expression and
  *					put the result into a variable.
+ *
+ * For no very good reason, this is also used for PERFORM statements.
  * ----------
  */
 static int
 exec_stmt_assign(PLpgSQL_execstate * estate, PLpgSQL_stmt_assign * stmt)
 {
-	if (stmt->varno < 0)
-		exec_assign_expr(estate, NULL, stmt->expr);
+	PLpgSQL_expr   *expr = stmt->expr;
+
+	if (stmt->varno >= 0)
+		exec_assign_expr(estate, estate->datums[stmt->varno], expr);
 	else
-		exec_assign_expr(estate, estate->datums[stmt->varno], stmt->expr);
+	{
+		/*
+		 * PERFORM: evaluate query and discard result.  This cannot share
+		 * code with the assignment case since we do not wish to constraint
+		 * the discarded result to be only one row/column.
+		 */
+		int			rc;
+
+		SPI_tuptable = NULL;
+		SPI_processed = 0;
+
+		/*
+		 * If not already done create a plan for this expression
+		 */
+		if (expr->plan == NULL)
+			exec_prepare_plan(estate, expr);
+
+		rc = exec_run_select(estate, expr, 0, NULL);
+		if (rc != SPI_OK_SELECT)
+			elog(ERROR, "query \"%s\" didn't return data", expr->query);
+
+		SPI_freetuptable(SPI_tuptable);
+	}
 
 	return PLPGSQL_RC_OK;
 }
@@ -2608,8 +2634,7 @@ exec_assign_expr(PLpgSQL_execstate * estate, PLpgSQL_datum * target,
 	bool		isnull = false;
 
 	value = exec_eval_expr(estate, expr, &isnull, &valtype);
-	if (target != NULL)
-		exec_assign_value(estate, target, value, valtype, &isnull);
+	exec_assign_value(estate, target, value, valtype, &isnull);
 
 	SPI_freetuptable(SPI_tuptable);
 }