Manually merged

mysql-test/r/insert_select.result

@@ -686,3 +686,7 @@ ERROR 42S22: Unknown column 'z' in 'field list'
 insert into t1(x,y) select x,z from t2 on duplicate key update x=values(t2.x);
 ERROR 42S22: Unknown column 't2.x' in 'field list'
 drop table t1,t2;
+CREATE TABLE t1 (a int PRIMARY KEY);
+INSERT INTO t1 values (1), (2);
+INSERT INTO t1 SELECT a + 2 FROM t1 LIMIT 1;
+DROP TABLE t1;

mysql-test/t/insert_select.test

@@ -224,4 +224,17 @@ insert into t1(x,y) select x,z from t2 on duplicate key update x=values(z);
 insert into t1(x,y) select x,z from t2 on duplicate key update x=values(t2.x);
 drop table t1,t2; 
 
+#
+# Bug #9676: INSERT INTO x SELECT .. FROM x LIMIT 1; slows down with big 
+#             tables
+#
+
+#Note: not an exsaustive test : just a check of the code path.
+CREATE TABLE t1 (a int PRIMARY KEY);
+INSERT INTO t1 values (1), (2);
+
+INSERT INTO t1 SELECT a + 2 FROM t1 LIMIT 1;
+
+DROP TABLE t1;
+
 # End of 4.1 tests

sql/sql_select.cc

@@ -1068,8 +1068,9 @@ JOIN::optimize()
 			   group_list ? 0 : select_distinct,
 			   group_list && simple_group,
 			   select_options,
-			   (order == 0 || skip_sort_order) ? select_limit :
-			   HA_POS_ERROR,
+			   (order == 0 || skip_sort_order || 
+                            test(select_options & OPTION_BUFFER_RESULT)) ? 
+                             select_limit : HA_POS_ERROR,
 			   (char *) "")))
       DBUG_RETURN(1);
 
@@ -8814,6 +8815,11 @@ create_tmp_table(THD *thd,TMP_TABLE_PARAM *param,List<Item> &fields,
       keyinfo->key_length+=  key_part_info->length;
     }
   }
+  else
+  {
+    set_if_smaller(table->max_rows, rows_limit);
+    param->end_write_records= rows_limit;
+  }
 
   if (distinct && field_count != param->hidden_field_count)
   {