ALTER SHARDING KEY GENERATE STRATEGY

Description

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

Syntax

AlterShardingKeyGenerateStrategy ::=
  'ALTER' 'SHARDING' 'KEY' 'GENERATE' 'STRATEGY' keyGenerateStrategyName '(' keyGenerateStrategyDefinition ')'

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

The syntax structure is consistent with CREATE SHARDING KEY GENERATE STRATEGY;
ALTER replaces the existing sharding key generate strategy with the new definition;
GENERATOR=... is used to switch to an existing sharding key generator;
TYPE(NAME=..., PROPERTIES(...)) is used to switch to a new inline algorithm definition;
algorithmType is the key generate algorithm type. For details, refer to Distributed Primary Key.

Example

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

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

Alter to a sequence-based sharding key generate strategy with inline algorithm

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

Reserved word

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