Modify the partition-level hot cache policy

This topic describes how to modify the partition-level hot cache policy (STORAGE_CACHE_POLICY) by using SQL statements.

Considerations

You can modify the partition-level hot cache policy only in shared storage mode.

Modify the partition-level hot cache policy

After you create a partitioned table, you can use the ALTER TABLE statement to specify the STORAGE_CACHE_POLICY when you add partitions and to modify the STORAGE_CACHE_POLICY of existing partitions. The syntax is as follows:

• Specify the STORAGE_CACHE_POLICY when you add partitions:

  ALTER TABLE table_name
      ADD PARTITION (partition_list [STORAGE_CACHE_POLICY = {"hot" | "auto" | "none"}]);
  

• Modify the STORAGE_CACHE_POLICY of existing partitions:

  ALTER TABLE table_name
      ALTER PARTITION (partition_list [STORAGE_CACHE_POLICY = {"hot" | "auto" | "none"}]);
  

Parameters

The STORAGE_CACHE_POLICY at the partition level is an optional parameter. Valid values:

• hot: indicates that all data in the specified partition is hot data. If the cache disk space is sufficient, all data in the partition is cached to the local cache disk.
• auto: indicates that the hot data in the specified partition is automatically identified by the system.
• none: default value. The hot cache policy of the partition follows the value of the STORAGE_CACHE_POLICY at the upper level.

For more information about how to modify a partitioned table, see Add a partition and Modify a partition rule.

Examples

• Add a partition p2 to the tbl1 table. The hot data in the p2 partition is automatically identified by the system.

  ALTER TABLE tbl1 ADD PARTITION (PARTITION p2 VALUES LESS THAN(300) STORAGE_CACHE_POLICY = "auto");
  

• Modify the data in the p1 partition of the tbl1 table to hot data.

  ALTER TABLE tbl1 ALTER PARTITION p1 STORAGE_CACHE_POLICY = "hot";
  

• Modify the data in the sp3 subpartition of the tbl2 table to hot data. The hot data is automatically identified by the system.

  ALTER TABLE tbl2 ALTER SUBPARTITION sp3 STORAGE_CACHE_POLICY = "auto";
  

References

• Overview of custom hot cache policies
• Create a table-level hot cache policy
• Modify a table-level hot cache policy
• ALTER TABLE
• O&M guide for custom hot cache policies