时间旅行 'drop & recreate' table 保留期内过去的任何一天

Question

如果保留期为 30 天，但 table 每天被丢弃并重新创建，是否有可能看到 table 回溯 10 天的样子？

如果 table 被截断而不是重新创建，是否可以回到第 30 天？

Undrop 可能会恢复 table 被删除前的最新版本。是否可以恢复保留期内的任何版本？

Answer 1

是的，您可以查询 table 在其时间旅行期间的任何时间点。

Undrop 会将 table 恢复到被删除时的状态。

要在以前的时间点恢复 table，您需要使用 CREATE TABLE... CLONE...

Answer 2

如果保留期为 30 天，但 table 每天被删除并重新创建，是否有可能看到 table 回溯 10 天的样子?

UNDROP 命令仅恢复 table 的最新版本。但是@Pankaj 的测试表明，您仍然可以恢复任何尚未清除的掉落 table。

要查看历史上table的所有版本（已删除），您可以使用以下命令

SHOW TABLES HISTORY LIKE '<table_name>';

然后执行一系列 UNDROP 和 RENAME，直到恢复要恢复的 table 版本。

然而，这不是一个好的做法。如果您每天重新创建 table，请缩短其保留期限。如果要恢复 1 个月的历史记录，请执行截断而不是删除。

如果 table 被截断而不是重新创建，是否可以回到第 30 天？

是的。

create table tbl_clone clone tbl at (timestamp => dateadd('day',-30,current_timestamp()));

Undrop 可能恢复 table 被删除前的最新版本。是否可以恢复保留期内的任何版本？

是的，正如@Pankaj 已经提到和指出的那样。

Answer 3

这是一个有趣的问题。如果 table 被多次删除，我们可以执行 UNDROP。可以在这里找到一个很好的解释 - https://community.snowflake.com/s/article/Solution-Unable-to-access-Deleted-time-travel-data-even-within-retention-period

https://docs.snowflake.com/en/user-guide/data-time-travel.html?_ga=2.118857801.110877935.1647736580-83170813.1644772168&_gac=1.251330994.1646009703.EAIaIQobChMIuZ3o2Zeh9gIVjR-tBh3PvQUIEAAYASAAEgKYevD_BwE#example-dropping-and-restoring-a-table-multiple-times

我也测试了场景，如下图-

参考以下历史记录

SNOWFLAKE1#COMPUTE_WH@TEST_DB.PUBLIC>select query_id,query_text,start_time from table(information_schema.query_history()) where query_text like '%test_undrop_1%';
+--------------------------------------+-------------------------------------------------------------------------------------------------------------------------------+-------------------------------+
| QUERY_ID                             | QUERY_TEXT                                                                                                                    | START_TIME                    |
|--------------------------------------+-------------------------------------------------------------------------------------------------------------------------------+-------------------------------|
| 01a31a99-0000-81fe-0001-fa120003d75e | select query_id,query_text,start_time from table(information_schema.query_history()) where query_text like '%test_undrop_1%'; | 2022-03-22 14:13:58.953 -0700 |
| 01a31a99-0000-81c6-0001-fa120003f7ee | drop table test_undrop_1;                                                                                                     | 2022-03-22 14:13:55.098 -0700 |
| 01a31a99-0000-81fe-0001-fa120003d73e | create or replace table test_undrop_1(id number, name varchar2(10));                                                          | 2022-03-22 14:13:53.425 -0700 |
| 01a31a99-0000-81fe-0001-fa120003d72a | drop table test_undrop_1;                                                                                                     | 2022-03-22 14:13:46.968 -0700 |
| 01a31a99-0000-81c6-0001-fa120003f79e | create or replace table test_undrop_1(id1 number, name varchar2(10));                                                         | 2022-03-22 14:13:44.002 -0700 |
| 01a31a99-0000-81fe-0001-fa120003d70e | drop table test_undrop_1;                                                                                                     | 2022-03-22 14:13:36.078 -0700 |
| 01a31a99-0000-81c6-0001-fa120003f77e | select query_id,query_text,start_time from table(information_schema.query_history()) where query_text like '%test_undrop_1%'; | 2022-03-22 14:13:14.711 -0700 |
| 01a31a99-0000-81fe-0001-fa120003d70a | select count(*) from test_undrop_1;                                                                                           | 2022-03-22 14:13:04.640 -0700 |
| 01a31a98-0000-81fe-0001-fa120003d706 | select * from test_undrop_1;                                                                                                  | 2022-03-22 14:12:52.230 -0700 |
| 01a31a98-0000-81c6-0001-fa120003f75e | create or replace table test_undrop_1(id1 number, name1 varchar2(10));                                                        | 2022-03-22 14:12:43.734 -0700 |
+--------------------------------------+-------------------------------------------------------------------------------------------------------------------------------+-------------------------------+

SNOWFLAKE1#COMPUTE_WH@TEST_DB.PUBLIC>select * from test_undrop_1;
+----+------+
| ID | NAME |
|----+------|
+----+------+
0 Row(s) produced. Time Elapsed: 0.760s
SNOWFLAKE1#COMPUTE_WH@TEST_DB.PUBLIC>alter table TEST_UNDROP_1 rename to test_undrop_1_1;
+----------------------------------+
| status                           |
|----------------------------------|
| Statement executed successfully. |
+----------------------------------+
1 Row(s) produced. Time Elapsed: 0.142s

UNDROP-1

SNOWFLAKE1#COMPUTE_WH@TEST_DB.PUBLIC>undrop table test_undrop_1;
+--------------------------------------------+
| status                                     |
|--------------------------------------------|
| Table TEST_UNDROP_1 successfully restored. |
+--------------------------------------------+
1 Row(s) produced. Time Elapsed: 0.155s
SNOWFLAKE1#COMPUTE_WH@TEST_DB.PUBLIC>select * from test_undrop_1;
+----+------+
| ID | NAME |
|----+------|
+----+------+
0 Row(s) produced. Time Elapsed: 0.223s
SNOWFLAKE1#COMPUTE_WH@TEST_DB.PUBLIC>alter table TEST_UNDROP_1 rename to test_undrop_1_2;
+----------------------------------+
| status                           |
|----------------------------------|
| Statement executed successfully. |
+----------------------------------+
1 Row(s) produced. Time Elapsed: 0.191s

UNDROP-2

SNOWFLAKE1#COMPUTE_WH@TEST_DB.PUBLIC>undrop table test_undrop_1;
+--------------------------------------------+
| status                                     |
|--------------------------------------------|
| Table TEST_UNDROP_1 successfully restored. |
+--------------------------------------------+
1 Row(s) produced. Time Elapsed: 0.155s
SNOWFLAKE1#COMPUTE_WH@TEST_DB.PUBLIC>select * from test_undrop_1;
+-----+------+
| ID1 | NAME |
|-----+------|
+-----+------+
0 Row(s) produced. Time Elapsed: 0.140s
SNOWFLAKE1#COMPUTE_WH@TEST_DB.PUBLIC>alter table TEST_UNDROP_1 rename to test_undrop_1_3;
+----------------------------------+
| status                           |
|----------------------------------|
| Statement executed successfully. |
+----------------------------------+
1 Row(s) produced. Time Elapsed: 0.396s

UNDROP-3（是的！得到了我的 table 版本）

SNOWFLAKE1#COMPUTE_WH@TEST_DB.PUBLIC>undrop table test_undrop_1;
+--------------------------------------------+
| status                                     |
|--------------------------------------------|
| Table TEST_UNDROP_1 successfully restored. |
+--------------------------------------------+
1 Row(s) produced. Time Elapsed: 0.149s
SNOWFLAKE1#COMPUTE_WH@TEST_DB.PUBLIC>select * from test_undrop_1;
+-----+-------+
| ID1 | NAME1 |
|-----+-------|
+-----+-------+
0 Row(s) produced. Time Elapsed: 0.178s

时间旅行 'drop & recreate' table 保留期内过去的任何一天

Time travelling a 'drop & recreate' table for any past day within retention period

time-travel

snowflake-cloud-data-platform

参考以下历史记录

UNDROP-1

UNDROP-2

UNDROP-3（是的！得到了我的 table 版本）