Merge mysql-5.1 to mysql-5.5.

storage/innobase/ibuf/ibuf0ibuf.c

@@ -3604,11 +3604,18 @@ ibuf_insert_low(
 
 		root = ibuf_tree_root_get(&mtr);
 
-		err = btr_cur_pessimistic_insert(BTR_NO_LOCKING_FLAG
-						 | BTR_NO_UNDO_LOG_FLAG,
-						 cursor,
-						 ibuf_entry, &ins_rec,
-						 &dummy_big_rec, 0, thr, &mtr);
+		err = btr_cur_optimistic_insert(
+			BTR_NO_LOCKING_FLAG | BTR_NO_UNDO_LOG_FLAG,
+			cursor, ibuf_entry, &ins_rec,
+			&dummy_big_rec, 0, thr, &mtr);
+
+		if (err == DB_FAIL) {
+			err = btr_cur_pessimistic_insert(
+				BTR_NO_LOCKING_FLAG | BTR_NO_UNDO_LOG_FLAG,
+				cursor, ibuf_entry, &ins_rec,
+				&dummy_big_rec, 0, thr, &mtr);
+		}
+
 		mutex_exit(&ibuf_pessimistic_insert_mutex);
 		ibuf_size_update(root, &mtr);
 		mutex_exit(&ibuf_mutex);

storage/innobase/row/row0ins.c

@@ -2168,9 +2168,16 @@ row_ins_index_entry_low(
 
 				goto function_exit;
 			}
-			err = btr_cur_pessimistic_insert(
+
+			err = btr_cur_optimistic_insert(
 				0, &cursor, entry, &insert_rec, &big_rec,
 				n_ext, thr, &mtr);
+
+			if (err == DB_FAIL) {
+				err = btr_cur_pessimistic_insert(
+					0, &cursor, entry, &insert_rec,
+					&big_rec, n_ext, thr, &mtr);
+			}
 		}
 	}