Hot and Cold Table Functions

pg_obs_cold_refresh_time(table_name, time)

Description: Modifies the time when cold data in a hot and cold table is migrated to OBS. The default value is 00:00 every day.

table_name indicates the name of the hot and cold table, and the type is Name. time indicates the time when the data switchover task is scheduled, and the type is Time.

Return value: SUCCESS, which indicates that the time is successfully modified.

Example:

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SELECT * FROM pg_obs_cold_refresh_time('lifecycle_table', '06:30:00');
pg_obs_cold_refresh_time
--------------------------
 SUCCESS
(1 row)

pg_refresh_storage()

Description: Switches hot data to cold data on all hot and cold tables (in OBS).

Return type: int

Columns in the returned value:

• success_count int: indicates the number of tables that are successfully switched.
• failed_count int: indicates the number of tables that fail to be switched.

Example:

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SELECT * FROM pg_refresh_storage();
 success_count | failed_count
---------------+--------------
             1 |            0
(1 row)

pg_lifecycle_table_data_distribute(table_name)

Description: Views the data distribution of a cold and hot table.

table_name indicates the table name and cannot be left blank.

Return value: record

Example: Multiple records are generated based on the number of nodes. The following example shows the data distribution in the w1 table when there is only one DN node.

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SELECT * FROM pg_catalog.pg_lifecycle_table_data_distribute('w1');
 schemaname | tablename | nodename | hotpartition | coldpartition | switchablepartition | hotdatasize | colddatasize | switchabledatasize 
------------+-----------+----------+--------------+---------------+---------------------+-------------+--------------+--------------------
 public     | w1        | dn_1     | p2           | p1            |                     | 80 KB       | 0 bytes      | 0 bytes
(1 row)

pg_lifecycle_node_data_distribute()

Description: Views the data distribution of all hot and cold tables.

Return value: record

Example: There are two cold and hot tables in the database. The data distribution is as follows:

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SELECT * FROM pg_catalog.pg_lifecycle_node_data_distribute();
 schemaname | tablename | nodename | hotpartition | coldpartition | switchablepartition | hotdatasize | colddatasize | switchabledatasize 
------------+-----------+----------+--------------+---------------+---------------------+-------------+--------------+--------------------
 public     | w1        | dn_1     | p2           | p1            |                     |       81920 |            0 |                  0
 public     | w2        | dn_1     | p2           | p1            |                     |       81920 |            0 |                  0
(2 rows)

refresh_hot_storage(relname text)

Description: Flushes all partition data of a specified cold and hot table to OBS. The returned value is the number of switched partitions. This function is supported only in 8.2.1.100 or later.

Parameter:

relname: table name (name of a cold and hot table. If the name of a non-cold and hot table is used, no error is reported and 0 is returned.)

Return type: integer

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SELECT refresh_hot_storage('multi_temper_table');
 refresh_hot_storage
---------------------
            4
(1 row)

refresh_hot_storage(relname text, partname text)

Description: Synchronizes partition data of a specified hot and cold table to OBS. The returned value is the number of switched partitions. This function is supported only in 8.2.1.100 or later.

Parameter:

• relname: table name (name of a cold and hot table. If the name of a non-cold and hot table is used, no error is reported and 0 is returned.)
• partname: partition name (specifies a partition name of a cold and hot table)

Return type: integer

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SELECT refresh_hot_storage('multi_temper_table','p1');
 refresh_hot_storage
---------------------
            1
(1 row)

reload_cold_partition(relname text)

Description: This function converts all cold partitions to hot ones. The returned value is the number of switched partitions. This function is supported only by 8.3.0 and later versions.

Parameter:

relname: table name (name of a cold and hot table. If the name of a non-cold and hot table is used, no error is reported and 0 is returned.)

Return type: integer

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SELECT reload_cold_partition('multi_temper_table');
 reload_cold_partition
---------------------
            4
(1 row)

reload_cold_partition(relname text, partname text)

Description: This function converts specific cold partitions to hot ones. The returned value is the number of switched partitions. This function is supported only by 8.3.0 and later versions.

Parameter:

• relname: table name (name of a cold and hot table. If the name of a non-cold and hot table is used, no error is reported and 0 is returned.)
• partname: partition name (specifies a partition name of a cold and hot table)

Return type: integer

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SELECT reload_cold_partition('multi_temper_table','p1');
 reload_cold_partition
---------------------
            1
(1 row)