1 files changed, 35 insertions, 22 deletions

diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index 8d3fecf6d6a..c10d891260c 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -883,10 +883,9 @@ exec_simple_query(const char *query_string)
 	ListCell   *parsetree_item;
 	bool		save_log_statement_stats = log_statement_stats;
 	bool		was_logged = false;
-	bool		isTopLevel;
+	bool		use_implicit_block;
 	char		msec_str[32];
 
-
 	/*
 	 * Report query to various monitoring facilities.
 	 */
@@ -947,13 +946,14 @@ exec_simple_query(const char *query_string)
 	MemoryContextSwitchTo(oldcontext);
 
 	/*
-	 * We'll tell PortalRun it's a top-level command iff there's exactly one
-	 * raw parsetree.  If more than one, it's effectively a transaction block
-	 * and we want PreventTransactionChain to reject unsafe commands. (Note:
-	 * we're assuming that query rewrite cannot add commands that are
-	 * significant to PreventTransactionChain.)
+	 * For historical reasons, if multiple SQL statements are given in a
+	 * single "simple Query" message, we execute them as a single transaction,
+	 * unless explicit transaction control commands are included to make
+	 * portions of the list be separate transactions.  To represent this
+	 * behavior properly in the transaction machinery, we use an "implicit"
+	 * transaction block.
 	 */
-	isTopLevel = (list_length(parsetree_list) == 1);
+	use_implicit_block = (list_length(parsetree_list) > 1);
 
 	/*
 	 * Run through the raw parsetree(s) and process each one.
@@ -1001,6 +1001,16 @@ exec_simple_query(const char *query_string)
 		/* Make sure we are in a transaction command */
 		start_xact_command();
 
+		/*
+		 * If using an implicit transaction block, and we're not already in a
+		 * transaction block, start an implicit block to force this statement
+		 * to be grouped together with any following ones.  (We must do this
+		 * each time through the loop; otherwise, a COMMIT/ROLLBACK in the
+		 * list would cause later statements to not be grouped.)
+		 */
+		if (use_implicit_block)
+			BeginImplicitTransactionBlock();
+
 		/* If we got a cancel signal in parsing or prior command, quit */
 		CHECK_FOR_INTERRUPTS();
 
@@ -1098,7 +1108,7 @@ exec_simple_query(const char *query_string)
 		 */
 		(void) PortalRun(portal,
 						 FETCH_ALL,
-						 isTopLevel,
+						 true,	/* always top level */
 						 true,
 						 receiver,
 						 receiver,
@@ -1108,15 +1118,7 @@ exec_simple_query(const char *query_string)
 
 		PortalDrop(portal, false);
 
-		if (IsA(parsetree->stmt, TransactionStmt))
-		{
-			/*
-			 * If this was a transaction control statement, commit it. We will
-			 * start a new xact command for the next command (if any).
-			 */
-			finish_xact_command();
-		}
-		else if (lnext(parsetree_item) == NULL)
+		if (lnext(parsetree_item) == NULL)
 		{
 			/*
 			 * If this is the last parsetree of the query string, close down
@@ -1124,9 +1126,18 @@ exec_simple_query(const char *query_string)
 			 * is so that any end-of-transaction errors are reported before
 			 * the command-complete message is issued, to avoid confusing
 			 * clients who will expect either a command-complete message or an
-			 * error, not one and then the other.  But for compatibility with
-			 * historical Postgres behavior, we do not force a transaction
-			 * boundary between queries appearing in a single query string.
+			 * error, not one and then the other.  Also, if we're using an
+			 * implicit transaction block, we must close that out first.
+			 */
+			if (use_implicit_block)
+				EndImplicitTransactionBlock();
+			finish_xact_command();
+		}
+		else if (IsA(parsetree->stmt, TransactionStmt))
+		{
+			/*
+			 * If this was a transaction control statement, commit it. We will
+			 * start a new xact command for the next command.
 			 */
 			finish_xact_command();
 		}
@@ -1149,7 +1160,9 @@ exec_simple_query(const char *query_string)
 	}							/* end loop over parsetrees */
 
 	/*
-	 * Close down transaction statement, if one is open.
+	 * Close down transaction statement, if one is open.  (This will only do
+	 * something if the parsetree list was empty; otherwise the last loop
+	 * iteration already did it.)
 	 */
 	finish_xact_command();