oracle partition table delete partition

Oracle is currently the most widely used relational database management system. It supports partitioned table operations. Partitioned tables are one of the effective ways to enhance table performance. When business data grows rapidly, deleting partitions from a partitioned table is an essential operation. This article will introduce in detail the methods and precautions for deleting partitions from an Oracle partitioned table.

1. Partitioned table

Partitioned table is a very practical table type in Oracle database. It divides the table into several parts according to logical or physical standards, and each part has its own physical structure. In this way, the split table can make full use of the parallel query, distributed query, read-write separation and other features of the Oracle database to improve the performance and scalability of the database. Among them, partition representation can be based on time, range, hash, list, etc.

2. Partition table deletion

In actual business operations, due to the rapid growth of data, the database storage space will be insufficient. In order to release storage space and improve database performance, the partition table needs to be deleted. Perform a delete operation. Deleting partitions from a partition table can be performed manually or through a script.

1. Manual deletion of partitions

Manual deletion of partitions requires the following steps:

1. First confirm the storage location of the partition table, you can use the following SQL Statement view:

SELECT table_name, partition_name, segment_name, partition_position, tablespace_name

FROM user_tab_partitions

WHERE table_name = 'table name';

2. Execute The following statement deletes the specified partition:

ALTER TABLE table name DROP PARTITION partition name;

For example, to delete the partition with the table name EMPLOYEE and the partition name P01, you can execute the following statement:

ALTER TABLE EMPLOYEE DROP PARTITION P01;

3. Query the storage location of the partition table again and verify the deletion result:

SELECT table_name, partition_name, segment_name, partition_position, tablespace_name

FROM user_tab_partitions

WHERE table_name = 'table name';

If the specified partition is deleted successfully, the P01 partition will no longer be found in the query results.

2. Deleting partitions through scripts

Deleting partitions through scripts has the advantages of batch processing and automation. Deleting partition tables through scripts can reduce manual operation time and error rates.

The following is a sample code for a script to delete a partition:

DECLARE

c_date DATE := to_date('2019-01-01', 'yyyy-mm-dd') ;

c_max_partition_interval NUMBER := 6;

c_cur_part_date DATE;

c_del_partition_name VARCHAR2(30);

c_del_partition_cnt NUMBER := 0;

BEGIN

c_cur_part_date := add_months(sysdate, -1 * c_max_partition_interval);

LOOP

IF c_cur_part_date <= c_date THEN

exit;

END IF;

SELECT partition_name INTO c_del_partition_name FROM user_tab_partitions

WHERE table_name = 'Partition table name' AND TO_DATE(SUBSTR(partition_name, -8), 'yyyymmdd') < c_cur_part_date;

IF c_del_partition_name IS NOT NULL THEN

EXECUTE IMMEDIATE 'ALTER TABLE partition table name DROP PARTITION '||c_del_partition_name;

c_del_partition_cnt := c_del_partition_cnt 1;

END IF;

c_cur_part_date := add_months(c_cur_part_date, 1);

END LOOP;

DBMS_OUTPUT.PUT_LINE('Delete the number of partitions in the partition table: '||c_del_partition_cnt);

END;

The code logic of the script to delete the partition is as follows:

1. Define the basic information of the partition table, which are the partition table name and time. stamp domain, and the maximum number of partition intervals.

2. Define the loop variable c_cur_part_date, which is used to record the current timestamp field.

3. Enter the loop, query the partition table and delete the partition according to the timestamp field. If the partition that should be deleted currently does not exist, exit the loop.

4. Update the timestamp field of c_cur_part_date for the next round of loop processing.

5. Output the number of partitions deleted this time.

3. Notes

When deleting partition table partitions, you need to pay attention to the following issues:

1. Deleting a partition in the partition table will permanently delete the data. Be sure to confirm whether the data is Can be permanently removed.

2. A large number of log files will be generated during the deletion process, and the reserved space and cleanup of the log files need to be considered.

3. Deleting the partitions of the partition table will cause fragmentation of the table space, which requires table space recycling and defragmentation.

4. During the deletion process, the data insertion operation of the partition table needs to be turned off to avoid affecting the data being inserted.

4. Summary

For business scenarios that require large amounts of data storage, partition tables are one of the necessary means to optimize database performance. Deleting partition table partitions can release storage space and optimize partition table queries. And maintenance. In actual operation, partitions can be deleted manually or partitions can be automatically deleted in batches through scripts. No matter which method is used, data security and the impact on the business need to be fully considered to ensure the stability and reliability of the deletion operation.

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