Add integration test for div_precision_increment support

tests/fullstack-test2/variables/set_variable_div_precision_increment.test

@@ -0,0 +1,58 @@
+# Copyright 2024 PingCAP, Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+## test correctness in simple case
+mysql> drop table if exists test.t
+mysql> create table test.t (a decimal(3, 1), b decimal(3, 0))
+mysql> alter table test.t set tiflash replica 1
+
+func> wait_table test t
+
+mysql> insert into test.t values(11.2,3);
+mysql> insert into test.t values(10.1,3);
+mysql> insert into test.t values(13.7,3);
+
+mysql> set session tidb_isolation_read_engines='tiflash'; set tidb_enforce_mpp = 1; select a/b from test.t;
++---------+
+| a/b     |
++---------+
+| 3.73333 |
+| 3.36667 |
+| 4.56667 |
++---------+
+
+mysql> mysql> set session tidb_isolation_read_engines='tiflash'; set tidb_enforce_mpp = 1; select avg(a) from test.t group by b;
++----------+
+| avg(a)   |
++----------+
+| 11.66667 |
++----------+
+
+mysql> set session tidb_isolation_read_engines='tiflash'; set tidb_enforce_mpp = 1; set div_precision_increment = 5; select a/b from test.t;
++----------+
+| a/b      |
++----------+
+| 3.733333 |
+| 3.366667 |
+| 4.566667 |
++----------+
+
+mysql> mysql> set session tidb_isolation_read_engines='tiflash'; set tidb_enforce_mpp = 1; set div_precision_increment = 5; select avg(a) from test.t group by b;
++-----------+
+| avg(a)    |
++-----------+
+| 11.666667 |
++-----------+
+
+mysql> drop table if exists test.t