Flashback in GBase 8c for Data Consistency

gs_guc set -N all -I all -c "undo_zone_count=16384"           ## Number of undo zones allocatable in memory, 0 means undo and Ustore tables are disabled, recommended value is max_connections*4
gs_guc set -N all -I all -c "enable_default_ustore_table=on"  ## Enable default support for the Ustore storage engine
gs_guc set -N all -I all -c "version_retention_age=10000"     ## Number of transactions for which old versions are retained, versions beyond this count will be cleaned up

ALTER SYSTEM SET undo_zone_count=16384;
ALTER SYSTEM SET enable_default_ustore_table=on;
ALTER SYSTEM SET version_retention_age=10000;

gs_guc set -N all -I all -c "enable_recyclebin=on"            ## Enable the recycle bin
gs_guc set -N all -I all -c "recyclebin_retention_time=15min" ## Set the retention time for recycle bin objects, objects beyond this time will be automatically cleaned up

gs_om -t restart

postgres=# drop table if exists t1;
postgres=# create table t1(a int,b int,c int,d int);
postgres=# insert into t1 values(1,2,3,4),(21,22,23,24),(31,32,33,34);

postgres=# select * from t1;

postgres=# select current_timestamp;
  pg_systimestamp
------------------------------
2021-10-12 10:03:08.272344+08

postgres=# update t1 set a=99;
postgres=# select * from t1;
a  | b  | c  | d
----+----+----+----
99 |  2 |  3 |  4
99 | 22 | 23 | 24
99 | 32 | 33 | 34

postgres=# select snptime,snpcsn from gs_txn_snapshot where snptime between '2022-04-21 13:39:36.007842+08' and '2022-04-21 13:39:39.007842+08';
postgres=# select * from t1 timecapsule timestamp to_timestamp('2022-04-21 13:39:38.540667+08','YYYY-MM-DD HH24:MI:SS.FF');
a  | b  | c  | d
----+----+----+----
 1 |  2 |  3 |  4
21 | 22 | 23 | 24
31 | 32 | 33 | 34

postgres=# select * from t1 timecapsule csn 417232;
a  | b  | c  | d
----+----+----+----
 1 |  2 |  3 |  4
21 | 22 | 23 | 24
31 | 32 | 33 | 34
postgres=# SELECT rcyname,rcyoriginname,rcytablespace FROM GS_RECYCLEBIN;
      rcyname           | rcyoriginname | rcytablespace
-----------------------------+---------------+---------------
BIN$3BFF4EB403B$4C71318==$0 | t2            |             0   -- Note: Only the t2 table stored in Astore is visible; the t1 table stored in Ustore is not visible.
(1 row)

postgres=# timecapsule table t1 to before drop rename to t1_bak;
# The return message "TimeCapsule Table" indicates successful execution.

postgres=# select * from t2_bak;
id |   name
----+----------
1 | t2_Tom
2 | t2_Jerry

postgres=# create table t_astore(id int,col1 varchar(8)) with (storage_type=astore);
postgres=# create table t_ustore(id int,col1 varchar(8));
postgres=# insert into t_ustore values(1,'u1'),(2,'u2');
postgres=# select now();
postgres=# update t_ustore set col1='uu' where id=2;
postgres=# select now();
postgres=# delete from t_ustore;
postgres=# select now();
postgres=# select * from t_ustore ;

postgres=# select * from t_ustore timecapsule timestamp to_timestamp('2022-03-20 23:33:41','YYYY-MM-DD HH24:MI:SS.FF');
id | col1
----+------
 1 | u1
 2 | u2
(2 rows)


postgres=# select * from t_ustore timecapsule timestamp to_timestamp('2022-03-20 23:34:04','YYYY-MM-DD HH24:MI:SS.FF');
id | col1
----+------
 1 | u1
 2 | uu
(2 rows)

postgres=# select * into t from t_ustore timecapsule timestamp to_timestamp('2022-03-20 23:34:04','YYYY-MM-DD HH24:MI:SS.FF');
postgres=# select * from t;
id | col1
----+------
 1 | u1
 2 | uu
(2 rows)