MySQL optimizer optional switch details

Welcome to the Linux community forum and interact with 2 million technical staff to access MySQL from 5.1 and provide the switch options for optimizer options. In this way, when the optimizer is confused, we can disable something we think should not be done; or when we want to see why the optimizer needs to be selected, We can manually close or press

Welcome to the Linux community forum and interact with 2 million technicians> Start from MySQL 5.1 and provide the switch options for optimizer options. In this way, when the optimizer is confused, we can disable something we think should not be done; or when we want to see why the optimizer needs to be selected, We can manually close or press

Welcome to the Linux community forum and interact with 2 million technicians>

MySQL has provided the optimizer Option Switch option since 5.1. In this way, we can force some things that we think should not be done when the optimizer is confused, or when we want to see why the optimizer is so selective, you can manually disable or enable these options to change the optimization policy.

In MySQL 5.1, the following switch is added:

MySQL 5.5 adds the following switch:

In MySQL 5.6, the following switch is added:

1. mrr

2. batched_key_access

3. block_nested_loop

4. index_condition_pushdown

5. use_index_extensions

6. semijoin

Mysql> select B. class_name from class as B, student as a where. class_id = B. id; + ------------ + | class_name | + ------------ + | xinxi | + ------------ + 2 rows in set (0.00 sec)

7. firstmatch

8. loosescan

9. materialization