MySQL 虚拟列 Secondary Indexes and Generated Columns 基于列产生索引

mysql> CREATE TABLE jemp (
    ->     c JSON,
    ->     g INT GENERATED ALWAYS AS (c->"$.id"),
    ->     INDEX i (g)
    -> );
Query OK, 0 rows affected (0.28 sec)

mysql> INSERT INTO jemp (c) VALUES
     >   ('{"id": "1", "name": "Fred"}'), ('{"id": "2", "name": "Wilma"}'),
     >   ('{"id": "3", "name": "Barney"}'), ('{"id": "4", "name": "Betty"}');
Query OK, 4 rows affected (0.04 sec)
Records: 4  Duplicates: 0  Warnings: 0

mysql> SELECT c->>"$.name" AS name
     >     FROM jemp WHERE g > 2;
+--------+
| name   |
+--------+
| Barney |
| Betty  |
+--------+
2 rows in set (0.00 sec)

mysql> EXPLAIN SELECT c->>"$.name" AS name
     >    FROM jemp WHERE g > 2\G
*************************** 1. row ***************************
           id: 1
  select_type: SIMPLE
        table: jemp
   partitions: NULL
         type: range
possible_keys: i
          key: i
      key_len: 5
          ref: NULL
         rows: 2
     filtered: 100.00
        Extra: Using where
1 row in set, 1 warning (0.00 sec)

 

 

 

地址：https://dev.mysql.com/doc/refman/8.0/en/create-table-secondary-indexes.html