How Do I Delete Table Data Efficiently in GaussDB(DWS)?

Function

Functions

• TRUNCATE TABLE works like a DELETE statement with no WHERE clause, that is, emptying a table.
• TRUNCATE TABLE uses less system and transaction log resources.
  • DELETE deletes a row each time, and records each deletion in the transaction log.
  • TRUNCATE TABLE deletes all rows in a table by releasing the data page, and only records each releasing of the data page in the transaction log.
• TRUNCATE, DELETE, and DROP are different in that:
  • TRUNCATE TABLE deletes content, releases space, but does not delete definitions.
  • DELETE TABLE deletes content, but does not delete definitions or release space.
  • DROP TABLE deletes content and definitions, and releases space.

Examples

• Create a table.

  CREATE TABLE tpcds.reason_t1 AS TABLE tpcds.reason;
  
  

  Truncate the table.

  TRUNCATE TABLE tpcds.reason_t1;
  
  

  Delete the table.

  DROP TABLE tpcds.reason_t1;
  
  

• Create a partitioned table.

  CREATE TABLE tpcds.reason_p
  (
    r_reason_sk integer,
    r_reason_id character(16),
    r_reason_desc character(100)
  )PARTITION BY RANGE (r_reason_sk)
  (
    partition p_05_before values less than (05),
    partition p_15 values less than (15),
    partition p_25 values less than (25),
    partition p_35 values less than (35),
    partition p_45_after values less than (MAXVALUE)
  );
  
  

  Insert data.

  INSERT INTO tpcds.reason_p SELECT * FROM tpcds.reason;
  
  

  Truncate the p_05_before partition.

  ALTER TABLE tpcds.reason_p TRUNCATE PARTITION p_05_before;
  
  

  Truncate the partition p_15 where 13 is located.

  ALTER TABLE tpcds.reason_p TRUNCATE PARTITION for (13);
  
  

  Truncate the partitioned table.

  TRUNCATE TABLE tpcds.reason_p;
  
  

  Delete the table.

  DROP TABLE tpcds.reason_p;