ALTER DEFAULT SHARDING STRATEGY 语法用于修改默认的分片策略。
AlterDefaultShardingStrategy ::=
'ALTER' 'DEFAULT' 'SHARDING' ('DATABASE' | 'TABLE') 'STRATEGY' '(' shardingStrategy ')'
shardingStrategy ::=
'TYPE' '=' strategyType ',' ('SHARDING_COLUMN' '=' columnName | 'SHARDING_COLUMNS' '=' columnNames) ',' 'SHARDING_ALGORITHM' '=' algorithmDefinition
strategyType ::=
string
algorithmDefinition ::=
'TYPE' '(' 'NAME' '=' algorithmType ',' propertiesDefinition ')'
columnNames ::=
columnName (',' columnName)+
columnName ::=
identifier
algorithmType ::=
string
propertiesDefinition ::=
'PROPERTIES' '(' key '=' value (',' key '=' value)* ')'
key ::=
string
value ::=
literal
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。ALTER DEFAULT SHARDING TABLE STRATEGY (
TYPE="standard", SHARDING_COLUMN=user_id, SHARDING_ALGORITHM(TYPE(NAME=inline, PROPERTIES("algorithm-expression"="t_order_${user_id % 2}")))
);
ALTER、DEFAULT、SHARDING、DATABASE、TABLE、STRATEGY、TYPE、SHARDING_COLUMN、SHARDING_COLUMNS、SHARDING_ALGORITHM、NAME、PROPERTIES