where condition [on a.id = b.id where a.id =1 and b.id=1] can be optimized

[irene-coming]

• dble version：
  5.6.29-dble-2.20.04.99-997ff15fc20aaea4b1a0b5625619764dd22613a2-20200512052042

• preconditions ：

• configs：

schema.xml

                <table name="aly_test" dataNode="dn1,dn2,dn3,dn4" rule="hash-four" />
                <table name="a_manager" cacheKey="id" dataNode="dn2,dn1,dn4,dn3" rule="hash-four" />

rule.xml

server.xml

• steps：
  step1. explain in dble

mysql> explain select * from aly_test a join a_manager b on a.id = b.id where a.id =1 and b.id=1;
+-----------------+---------------+-------------------------------------------------------------------------------------------------------------+
| DATA_NODE       | TYPE          | SQL/REF                                                                                                     |
+-----------------+---------------+-------------------------------------------------------------------------------------------------------------+
| dn2_0           | BASE SQL      | select `a`.`id`,`a`.`c` from  `aly_test` `a` where (`a`.`id` = 1) AND (`a`.`id` = 1) ORDER BY `a`.`id` ASC  |
| merge_1         | MERGE         | dn2_0                                                                                                       |
| shuffle_field_1 | SHUFFLE_FIELD | merge_1                                                                                                     |
| dn1_0           | BASE SQL      | select `b`.`id`,`b`.`c` from  `a_manager` `b` where (`b`.`id` = 1) AND (`b`.`id` = 1) ORDER BY `b`.`id` ASC |
| merge_2         | MERGE         | dn1_0                                                                                                       |
| shuffle_field_3 | SHUFFLE_FIELD | merge_2                                                                                                     |
| join_1          | JOIN          | shuffle_field_1; shuffle_field_3                                                                            |
| shuffle_field_2 | SHUFFLE_FIELD | join_1                                                                                                      |
+-----------------+---------------+-------------------------------------------------------------------------------------------------------------+
8 rows in set (0.02 sec)

• expect result：
  1.the where condition may be optimized, maybe optimized as where (a.id = 1) , the current is: where (a.id = 1) AND (a.id = 1) where (b.id = 1) AND (b.id = 1)
• real result：
  1.
• supplements：
  1.related https://github.com/actiontech/dble/issues/752

[yanhuqing666]

It will cost more time to optimize， (need change com.actiontech.dble.plan.optimizer.FilterPusher)， just level it