CREATE DEFAULT SHARDING STRATEGY

Description

The CREATE DEFAULT SHARDING STRATEGY syntax is used to create a default sharding strategy

Syntax

Grammar Railroad diagram

CreateDefaultShardingStrategy ::=
  'CREATE' 'DEFAULT' 'SHARDING' ('DATABASE' | 'TABLE') 'STRATEGY' ifNotExists? '(' shardingStrategy ')'
ifNotExists ::=
  'IF' 'NOT' 'EXISTS'
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

Supplement

• When using the complex sharding algorithm, multiple sharding columns need to be specified using SHARDING_COLUMNS;
• algorithmType is the sharding algorithm type. For detailed sharding algorithm type information, please refer to Sharding Algorithm;
• ifNotExists clause is used for avoid Duplicate default sharding strategy error.

Example

• create a default sharding table strategy

-- create a default sharding table strategy
CREATE DEFAULT SHARDING TABLE STRATEGY (
    TYPE="standard", SHARDING_COLUMN=user_id, SHARDING_ALGORITHM(TYPE(NAME="inline", PROPERTIES("algorithm-expression"="t_order_${user_id % 2}")))
);

• create a default sharding table strategy with ifNotExists clause

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}")))
);

Reserved word

CREATE, DEFAULT, SHARDING, DATABASE, TABLE, STRATEGY, TYPE, SHARDING_COLUMN, SHARDING_COLUMNS, SHARDING_ALGORITHM, NAME, PROPERTIES

Related links

• Reserved word