Hologres:TRUNCATE

The TRUNCATE statement has the following limits:

• Hologres supports sequences. However, only CONTINUE IDENTITY is supported. RESTART IDENTITY is not supported.
• The TRUNCATE statement can be executed on a table and its child tables.
• The TRUNCATE statement cannot be executed on a foreign table.
• Only Hologres version 0.8 and later support the TRUNCATE statement. To obtain the latest version of Hologres, submit a ticket.

The TRUNCATE statement has the following syntax:

TRUNCATE [ TABLE ] name [, ... ]
    [CONTINUE IDENTITY ] 

The following table describes the parameters in the syntax.

Parameter	Description
CONTINUE IDENTITY	Do not change the values of sequences. Note Hologres supports only CONTINUE IDENTITY.

This section describes the examples of the TRUNCATE statement.

• Example 1: Create a table named event. Import data to the table and query the data. Execute the TRUNCATE TABLE event; statement to remove all data from the event table. The following statements provide an example:

  CREATE TABLE event (
      id int,
      name text,
      tag text
  );
  INSERT INTO event (id,name,tag) values (23,'buy', 'num');
  
  SELECT * FROM event;
  
  TRUNCATE TABLE event;

• Example 1: Create a table named \event_1. Import data to the table and query the data. Execute the TRUNCATE TABLE event_1 CONTINUE IDENTITY; statement to remove all data from the event_1 table without changing the values of sequences. The following statements provide an example:

  CREATE TABLE event_1 (
      id serial,
      name text,
      tag text
  );
  
  INSERT INTO event_1 (name,tag) values ('buy', 'num');
  
  SELECT * FROM event_1;
  
  # CONTINUE IDENTITY is the default value
  TRUNCATE TABLE event_1 CONTINUE IDENTITY;