CREATE DEFAULT SHARDING STRATEGY
描述
CREATE DEFAULT SHARDING STRATEGY 语法用于创建默认的分片策略。
语法定义
CreateDefaultShardingStrategy ::=
'CREATE' 'DEFAULT' 'SHARDING' ('DATABASE' | 'TABLE') 'STRATEGY' ifNotExists? '(' shardingStrategy ')'
ifNotExists ::=
'IF' 'NOT' 'EXISTS'
shardingStrategy ::=
'TYPE' '=' 'NONE'
| 'TYPE' '=' 'STANDARD' ',' 'SHARDING_COLUMN' '=' columnName ',' shardingAlgorithm
| 'TYPE' '=' 'COMPLEX' ',' 'SHARDING_COLUMNS' '=' columnName ',' columnName (',' columnName)* ',' shardingAlgorithm
| 'TYPE' '=' 'HINT' ',' shardingAlgorithm
shardingAlgorithm ::=
'SHARDING_ALGORITHM' '(' algorithmDefinition ')'
algorithmDefinition ::=
'TYPE' '(' 'NAME' '=' algorithmType (',' propertiesDefinition)? ')'
columnName ::=
identifier
algorithmType ::=
string
propertiesDefinition ::=
'PROPERTIES' '(' (key '=' value (',' key '=' value)*)? ')'
key ::=
string
value ::=
literal补充说明
- 当使用复合分片算法时，需要通过
SHARDING_COLUMNS指定多个分片键； algorithmType为分片算法类型，详细的分片算法类型信息请参考分片算法；ifNotExists子句用于避免出现Duplicate default sharding strategy错误。
示例
- 创建默认分表策略
CREATE DEFAULT SHARDING TABLE STRATEGY (
TYPE="standard", SHARDING_COLUMN=user_id, SHARDING_ALGORITHM(TYPE(NAME=inline, PROPERTIES("algorithm-expression"="t_order_${user_id % 2}")))
);- 使用
ifNotExists创建默认分表策略
CREATE DEFAULT SHARDING TABLE STRATEGY IF NOT EXISTS (
TYPE="standard", SHARDING_COLUMN=user_id, SHARDING_ALGORITHM(TYPE(NAME=inline, PROPERTIES("algorithm-expression"="t_order_${user_id % 2}")))
);保留字
CREATE、DEFAULT、SHARDING、DATABASE、TABLE、STRATEGY、TYPE、SHARDING_COLUMN、SHARDING_COLUMNS、SHARDING_ALGORITHM、NAME、PROPERTIES