ALTER PLACEMENT POLICY

Warning

Placement Rules in SQL is an experimental feature. The syntax might change before its GA, and there might also be bugs.

If you understand the risks, you can enable this experiment feature by executing SET GLOBAL tidb_enable_alter_placement = 1;.

ALTER PLACEMENT POLICY is used to modify existing placement policies that have previously been created. All the tables and partitions which use the placement policy will automatically be updated.

Synopsis

AlterPolicyStmt
ALTERPLACEMENTPOLICYIfExistsPolicyNamePlacementOptionList
PolicyName
Identifier
PlacementOptionList
DirectPlacementOptionPlacementOptionListDirectPlacementOptionPlacementOptionList,DirectPlacementOption
DirectPlacementOption
PRIMARY_REGIONEqOptstringLitREGIONSEqOptstringLitFOLLOWERSEqOptLengthNumVOTERSEqOptLengthNumLEARNERSEqOptLengthNumSCHEDULEEqOptstringLitCONSTRAINTSEqOptstringLitLEADER_CONSTRAINTSEqOptstringLitFOLLOWER_CONSTRAINTSEqOptstringLitVOTER_CONSTRAINTSEqOptstringLitLEARNER_CONSTRAINTSEqOptstringLit

Examples

Note

To know which regions are available in your cluster, see SHOW PLACEMENT LABELS.

If you do not see any available regions, your TiKV installation might not have labels set correctly.

CREATE PLACEMENT POLICY p1 PRIMARY_REGION="us-east-1" REGIONS="us-east-1,us-west-1";
ALTER PLACEMENT POLICY p1 PRIMARY_REGION="us-east-1" REGIONS="us-east-1,us-west-1,us-west-2" FOLLOWERS=4;
SHOW CREATE PLACEMENT POLICY p1\G
Query OK, 0 rows affected (0.08 sec)

Query OK, 0 rows affected (0.10 sec)

*************************** 1. row ***************************
       Policy: p1
Create Policy: CREATE PLACEMENT POLICY `p1` PRIMARY_REGION="us-east-1" REGIONS="us-east-1,us-west-1,us-west-2" FOLLOWERS=4
1 row in set (0.00 sec)

MySQL compatibility

This statement is a TiDB extension to MySQL syntax.

See also

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