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ALTER SHARDING TABLE RULE

Description

The ALTER SHARDING TABLE RULE syntax is used to alter sharding table rule for the currently selected database

Syntax

AlterShardingTableRule ::=
  'ALTER' 'SHARDING' 'TABLE' 'RULE' ( tableDefinition | autoTableDefinition ) ( ',' ( tableDefinition | autoTableDefinition ) )*

tableDefinition ::= 
   tableName '(' 'DATANODES' '(' dataNode ( ',' dataNode )* ')'  ( ','  'DATABASE_STRATEGY' '(' strategyDefinition ')' )?  ( ','  'TABLE_STRATEGY' '(' strategyDefinition ')' )?  ( ','  'KEY_GENERATE_STRATEGY' '(' keyGenerateStrategyDefinition ')' )? ')'

autoTableDefinition ::=
    tableName '(' 'RESOURCES' '(' resourceName ( ',' resourceName )*  ')' ',' 'SHARDING_COLUMN' '=' columnName ',' algorithmDefinition ( ','  'KEY_GENERATE_STRATEGY' '(' keyGenerateStrategyDefinition ')' )?')'

strategyDefinition ::=
  'TYPE' '=' strategyType ',' ( 'SHARDING_COLUMN' | 'SHARDING_COLUMNS' ) '=' columnName ',' algorithmDefinition

keyGenerateStrategyDefinition ::= 
  'KEY_GENERATE_STRATEGY' '(' 'COLUMN' '=' columnName ',' ( 'KEY_GENERATOR' '=' algorihtmName | algorithmDefinition ) ')' 

algorithmDefinition ::=
  ('SHARDING_ALGORITHM' '=' algorithmName | 'TYPE' '(' 'NAME' '=' algorithmType ( ',' 'PROPERTIES'  '(' propertyDefinition  ')' )?')'  )

propertyDefinition ::=
  ( key  '=' value ) ( ',' key  '=' value )* 
    
tableName ::=
  identifier

resourceName ::=
  identifier

columnName ::=
  identifier

algorithmName ::=
  identifier

Supplement

  • tableDefinition is defined for standard sharding table rule; autoTableDefinition is defined for auto sharding table rule. For standard sharding rules and auto sharding rule, refer to Data Sharding;
  • use standard sharding table rule:
    • DATANODES can only use resources that have been added to the current database, and can only use INLINE expressions to specify required resources;
    • DATABASE_STRATEGY, TABLE_STRATEGY are the database sharding strategy and the table sharding strategy, which are optional, and the default strategy is used when not configured;
    • The attribute TYPE in strategyDefinition is used to specify the type of Sharding Algorithm, currently only supports STANDARD, COMPLEX. Using COMPLEX requires specifying multiple sharding columns with SHARDING_COLUMNS.
  • use auto sharding table rule:
    • RESOURCES can only use resources that have been added to the current database, and the required resources can be specified by enumeration or INLINE expression;
    • Only auto sharding algorithm can be used, please refer to Auto Sharding Algorithm.
  • algorithmType is the sharding algorithm type, please refer to Sharding Algorithm;
  • The auto-generated algorithm naming rule is tableName _ strategyType _ shardingAlgorithmType;
  • The auto-generated primary key strategy naming rule is tableName _ strategyType;
  • KEY_GENERATE_STRATEGY is used to specify the primary key generation strategy, which is optional. For the primary key generation strategy, please refer to Distributed Primary Key.

Example

1.Standard sharding table rule

  • Alter standard sharding table rule to the specified sharding algorithms being altered
-- alter sharding algorithms
ALTER SHARDING ALGORITHM database_inline (
    TYPE(NAME="inline", PROPERTIES("algorithm-expression"="t_order_${user_id % 4}"))
), table_inline (
    TYPE(NAME="inline", PROPERTIES("algorithm-expression"="t_order_${order_id % 4}"))
); 

-- alter a sharding rule to the specified sharding algorithms being altered
ALTER SHARDING TABLE RULE t_order (
    DATANODES("resource_${0..3}.t_order_item${0..3}"),
    DATABASE_STRATEGY(TYPE="standard", SHARDING_COLUMN=user_id, SHARDING_ALGORITHM=database_inline),
    TABLE_STRATEGY(TYPE="standard", SHARDING_COLUMN=order_id, SHARDING_ALGORITHM=table_inline)
);
  • Use the altered default sharding database strategy, alter standard sharding table rule to the specified sharding algorithm being altered
-- alter sharding algorithms
ALTER SHARDING ALGORITHM database_inline (
    TYPE(NAME="inline", PROPERTIES("algorithm-expression"="t_order_${user_id % 4}"))
), table_inline (
    TYPE(NAME="inline", PROPERTIES("algorithm-expression"="t_order_${order_id % 4}"))
); 

-- alter a default sharding database strategy
ALTER DEFAULT SHARDING DATABASE STRATEGY (
    TYPE="standard", SHARDING_COLUMN=order_id, SHARDING_ALGORITHM=database_inline
);

-- alter a sharding table rule to the specified sharding algorithm being altered
ALTER SHARDING TABLE RULE t_order (
    DATANODES("resource_${0..3}.t_order_item${0..3}"),
    TABLE_STRATEGY(TYPE="standard", SHARDING_COLUMN=order_id, SHARDING_ALGORITHM=table_inline)
);
  • Use both the altered default sharding and the altered default sharding strategy, alter standard sharding table rule
-- alter sharding algorithms
ALTER SHARDING ALGORITHM database_inline (
    TYPE(NAME="inline", PROPERTIES("algorithm-expression"="t_order_${user_id % 4}"))
), table_inline (
    TYPE(NAME="inline", PROPERTIES("algorithm-expression"="t_order_${order_id % 4}"))
); 

-- alter a default sharding database strategy
ALTER DEFAULT SHARDING DATABASE STRATEGY (
    TYPE="standard", SHARDING_COLUMN=order_id, SHARDING_ALGORITHM=database_inline
);

-- alter a default sharding table strategy
ALTER DEFAULT SHARDING TABLE STRATEGY (
    TYPE="standard", SHARDING_COLUMN=order_id, SHARDING_ALGORITHM=table_inline
);

-- alter a sharding table rule
ALTER SHARDING TABLE RULE t_order (
    DATANODES("resource_${0..3}.t_order_item${0..3}")
);
  • Alter standard sharding table rule and create sharding algorithms at the same time
ALTER SHARDING TABLE RULE t_order (
    DATANODES("ds_${0..1}.t_order_${0..1}"),
    DATABASE_STRATEGY(TYPE="standard", SHARDING_COLUMN=user_id, SHARDING_ALGORITHM(TYPE(NAME="inline", PROPERTIES("algorithm-expression"="ds_${user_id % 2}")))),
    TABLE_STRATEGY(TYPE="standard", SHARDING_COLUMN=user_id, SHARDING_ALGORITHM(TYPE(NAME="inline", PROPERTIES("algorithm-expression"="ds_${order_id % 2}"))))
);

2.Auto sharding table rule

  • alter auto sharding table rule
ALTER SHARDING TABLE RULE t_order (
    RESOURCES(ds_0, ds_1),
    SHARDING_COLUMN=order_id, TYPE(NAME="MOD", PROPERTIES("sharding-count"="4"))
);

Reserved word

ALTER, SHARDING, TABLE, RULE, DATANODES, DATABASE_STRATEGY, TABLE_STRATEGY, KEY_GENERATE_STRATEGY, RESOURCES, SHARDING_COLUMN, TYPE, SHARDING_COLUMN, KEY_GENERATOR, SHARDING_ALGORITHM, COLUMN, NAME, PROPERTIES