Flashback Table

Context

Flashback table enables you to restore a table to a specific point in time. When only one table or a group of tables are logically damaged instead of the entire database, this feature can be used to quickly restore the table data. Based on the MVCC mechanism, the flashback table deletes incremental data at a specified time point and after the specified time point and retrieves the data deleted at the specified time point and the current time point to restore table-level data.

Prerequisites

The overall solution consists of three parts: earlier version retention, snapshot maintenance, and earlier version retrieval. Earlier version retention: The undo_retention_time parameter is added to set the retention period of an earlier version. The earlier version will be recycled and deleted after the retention period expires. For details, contact the administrator.

Syntax

TIMECAPSULE TABLE table_name TO { TIMESTAMP | CSN } expression

Examples

gaussdb=# DROP TABLE IF EXISTS "public".flashtest;
NOTICE:  table "flashtest" does not exist, skipping
DROP TABLE
-- Create a table.
gaussdb=# CREATE TABLE "public".flashtest (col1 INT,col2 TEXT) with(storage_type=ustore);
NOTICE:  The 'DISTRIBUTE BY' clause is not specified. Using 'col1' as the distribution column by default.
HINT:  Please use 'DISTRIBUTE BY' clause to specify suitable data distribution column.
CREATE TABLE
-- Query the CSN.
gaussdb=# SELECT int8in(xidout(next_csn)) FROM gs_get_next_xid_csn();
  int8in  
----------
 79352065
 79352065
 79352065
 79352065
 79352065
 79352065
(6 rows)
-- Query the current timestamp.
gaussdb=# SELECT now();
              now              
-------------------------------
 2023-09-13 19:46:34.102863+08
(1 row)
-- View the flashtest table.
gaussdb=# SELECT * FROM flashtest;
 col1 | col2 
------+------
(0 rows)
-- Insert data.
gaussdb=# INSERT INTO flashtest VALUES(1,'INSERT1'),(2,'INSERT2'),(3,'INSERT3'),(4,'INSERT4'),(5,'INSERT5'),(6,'INSERT6');
INSERT 0 6
gaussdb=# SELECT * FROM flashtest;
 col1 |  col2   
------+---------
    3 | INSERT3
    1 | INSERT1
    2 | INSERT2
    4 | INSERT4
    5 | INSERT5
    6 | INSERT6
(6 rows)
-- Flash a table back to a specific CSN.
gaussdb=# TIMECAPSULE TABLE flashtest TO CSN 79352065;
TimeCapsule Table
gaussdb=# SELECT * FROM flashtest;
 col1 | col2 
------+------
(0 rows)
gaussdb=# SELECT now();
              now              
-------------------------------
 2023-09-13 19:52:21.551028+08
(1 row)
-- Insert data.
gaussdb=# INSERT INTO flashtest VALUES(1,'INSERT1'),(2,'INSERT2'),(3,'INSERT3'),(4,'INSERT4'),(5,'INSERT5'),(6,'INSERT6');
INSERT 0 6
gaussdb=# SELECT * FROM flashtest;
 col1 |  col2   
------+---------
    3 | INSERT3
    6 | INSERT6
    1 | INSERT1
    2 | INSERT2
    4 | INSERT4
    5 | INSERT5
(6 rows)
-- Flash a table back to a specific timestamp.
gaussdb=# TIMECAPSULE TABLE flashtest TO TIMESTAMP to_timestamp ('2023-09-13 19:52:21.551028', 'YYYY-MM-DD HH24:MI:SS.FF');
TimeCapsule Table
gaussdb=# SELECT * FROM flashtest;
 col1 | col2 
------+------
(0 rows)
gaussdb=# select now();
              now              
-------------------------------
 2023-09-13 19:54:00.641506+08
(1 row)
-- Insert data.
gaussdb=# INSERT INTO flashtest VALUES(1,'INSERT1'),(2,'INSERT2'),(3,'INSERT3'),(4,'INSERT4'),(5,'INSERT5'),(6,'INSERT6');
INSERT 0 6
gaussdb=# SELECT * FROM flashtest;
 col1 |  col2   
------+---------
    3 | INSERT3
    6 | INSERT6
    1 | INSERT1
    2 | INSERT2
    4 | INSERT4
    5 | INSERT5
(6 rows)
-- Flash a table back to a specific timestamp.
gaussdb=# TIMECAPSULE TABLE flashtest TO TIMESTAMP '2023-09-13 19:54:00.641506';
TimeCapsule Table
gaussdb=# SELECT * FROM flashtest;
 col1 | col2 
------+------
(0 rows)
gaussdb=# DROP TABLE IF EXISTS "public".flashtest;
DROP TABLE