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' '=' 'NONE'
  | 'TYPE' '=' 'STANDARD' ',' 'SHARDING_COLUMN' '=' columnName ',' shardingAlgorithm
  | 'TYPE' '=' 'COMPLEX' ',' 'SHARDING_COLUMNS' '=' columnName ',' columnName (',' columnName)* ',' shardingAlgorithm
  | 'TYPE' '=' 'HINT' ',' shardingAlgorithm

shardingAlgorithm ::=
  'SHARDING_ALGORITHM' '(' algorithmDefinition ')'

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

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.

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

Reserved word