CREATE SHARDING KEY GENERATE STRATEGY

Description

The CREATE SHARDING KEY GENERATE STRATEGY syntax is used to create sharding key generate strategy for the currently selected database.

Syntax

CreateShardingKeyGenerateStrategy ::=
  'CREATE' 'SHARDING' 'KEY' 'GENERATE' 'STRATEGY' ifNotExists? keyGenerateStrategyName '(' keyGenerateStrategyDefinition ')'

ifNotExists ::=
  'IF' 'NOT' 'EXISTS'

keyGenerateStrategyDefinition ::=
  columnKeyGenerateStrategyDefinition
  | sequenceKeyGenerateStrategyDefinition

columnKeyGenerateStrategyDefinition ::=
  'TABLE' '=' tableName ',' 'COLUMN' '=' columnName ',' keyGenerateAlgorithmDefinition

sequenceKeyGenerateStrategyDefinition ::=
  'SEQUENCE' '=' sequenceName ',' keyGenerateAlgorithmDefinition

keyGenerateAlgorithmDefinition ::=
  algorithmDefinition
  | 'GENERATOR' '=' keyGeneratorName

algorithmDefinition ::=
  'TYPE' '(' 'NAME' '=' algorithmType (',' propertiesDefinition)? ')'

propertiesDefinition ::=
  'PROPERTIES' '(' (key '=' value (',' key '=' value)*)? ')'

key ::=
  string

value ::=
  literal

keyGenerateStrategyName ::=
  identifier

tableName ::=
  identifier

columnName ::=
  identifier

sequenceName ::=
  identifier | string

keyGeneratorName ::=
  identifier

algorithmType ::=
  string

Supplement

• columnKeyGenerateStrategyDefinition is used to define a key generate strategy based on logical table and column;
• sequenceKeyGenerateStrategyDefinition is used to define a key generate strategy based on sequence name;
• keyGenerateAlgorithmDefinition supports two styles:
  • Define key generate algorithm inline by TYPE(NAME=..., PROPERTIES(...));
  • Reference an existing sharding key generator by GENERATOR=...;
• When inline algorithm definition is used, the system will generate and bind the corresponding sharding key generator automatically;
• algorithmType is the key generate algorithm type. For details, refer to Distributed Primary Key;
• ifNotExists clause is used to avoid Duplicate sharding key generate strategy error.

Example

• Create a column-based sharding key generate strategy with inline algorithm definition

CREATE SHARDING KEY GENERATE STRATEGY order_id_strategy (
TABLE=t_order,
COLUMN=order_id,
TYPE(NAME="snowflake",PROPERTIES("worker-id"=1))
);

• Create a column-based sharding key generate strategy by referencing an existing key generator

CREATE SHARDING KEY GENERATE STRATEGY order_id_strategy (
TABLE=t_order,
COLUMN=order_id,
GENERATOR=snowflake_generator
);

• Create a sequence-based sharding key generate strategy

CREATE SHARDING KEY GENERATE STRATEGY order_sequence_strategy (
SEQUENCE="order_seq",
TYPE(NAME="uuid")
);

• Create sharding key generate strategy with ifNotExists clause

CREATE SHARDING KEY GENERATE STRATEGY IF NOT EXISTS order_id_strategy (
TABLE=t_order,
COLUMN=order_id,
GENERATOR=snowflake_generator
);

Reserved word

CREATE, SHARDING, KEY, GENERATE, STRATEGY, TABLE, COLUMN, SEQUENCE, TYPE, NAME, PROPERTIES, GENERATOR

Related links

• Reserved word
• SHOW SHARDING KEY GENERATE STRATEGY