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ALTER DEFAULT SHARDING STRATEGY

Description

The ALTER DEFAULT SHARDING STRATEGY syntax is used to alter a default sharding strategy

Syntax

AlterDefaultShardingStrategy ::=
  'ALTER' 'DEFAULT' 'SHARDING' ('DATABASE' | 'TABLE') 'STRATEGY' '(' shardingStrategy ')'

shardingStrategy ::=
  'TYPE' '=' strategyType ',' ( 'SHARDING_COLUMN' '=' columnName  | 'SHARDING_COLUMNS' '=' columnNames ) ',' ( 'SHARDING_ALGORITHM' '=' algorithmName | algorithmDefinition )

algorithmDefinition ::=
  'TYPE' '(' 'NAME' '=' algorithmType ',' 'PROPERTIES'  '(' propertyDefinition ')' ')'  

columnNames ::=
  columnName (',' columnName)+

columnName ::=
  identifier

algorithmName ::=
  identifier
  
algorithmType ::=
  string

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.

Example

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

Reserved word

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