ShardingSphere > Reference > DistSQL > Syntax > RDL Syntax > Rule Definition > Shadow > CREATE SHADOW RULE

CREATE SHADOW RULE

Description

The CREATE SHADOW RULE syntax is used to create a shadow rule.

Syntax

CreateShadowRule ::=
  'CREATE' 'SHADOW' 'RULE' shadowDefinition ( ',' shadowDefinition )*

shadowDefinition ::=
  ruleName '(' resourceMapping shadowTableRule ( ',' shadowTableRule )* ')'
    
resourceMapping ::=
    'SOURCE' '=' resourceName ',' 'SHADOW' '=' resourceName

shadowTableRule ::=
    tableName '(' shadowAlgorithm ( ',' shadowAlgorithm )* ')'
    
shadowAlgorithm ::=
    ( algorithmName ',' )? 'TYPE' '('  'NAME' '=' shadowAlgorithmType ',' 'PROPERTIES' '(' 'key' '=' 'value' ( ',' 'key' '=' 'value' ) ')'

ruleName ::=
  identifier

resourceName ::=
  identifier

tableName ::=
  identifier

algorithmName ::=
  identifier

shadowAlgorithmType ::=
  string

Supplement

Duplicate ruleName cannot be created;
resourceMapping specifies the mapping relationship between the source database and the shadow library. You need to use the resource managed by RDL, please refer to resource;
shadowAlgorithm can act on multiple shadowTableRule at the same time;
If algorithmName is not specified, it will be automatically generated according to ruleName, tableName and shadowAlgorithmType;
shadowAlgorithmType currently supports VALUE_MATCH, REGEX_MATCH and SIMPLE_HINT.

Example

Create a shadow rule

CREATE SHADOW RULE shadow_rule(
  SOURCE=demo_ds,
  SHADOW=demo_ds_shadow,
  t_order((simple_hint_algorithm, TYPE(NAME="SIMPLE_HINT", PROPERTIES("shadow"="true", "foo"="bar"))),(TYPE(NAME="REGEX_MATCH", PROPERTIES("operation"="insert","column"="user_id", "regex"='[1]')))), 
  t_order_item((TYPE(NAME="VALUE_MATCH", PROPERTIES("operation"="insert","column"="user_id", "value"='1'))))
);

Reserved word

CREATE, SHADOW, RULE, SOURCE, SHADOW, TYPE, NAME, PROPERTIES

Reserved word