Feat : undrop table & show history

[dantengsky]

I hereby agree to the terms of the CLA available at: https://databend.rs/dev/policies/cla/

Summary

undrop table .. and show tables history .. (legacy parser only)

• show tables history

mysql> drop table t4;
mysql> show tables history like 't4';
+-------------------+-------------------------------+
| Tables_in_default | drop_time                     |
+-------------------+-------------------------------+
| t4                | 2022-05-25 05:56:49.622 +0000 |
+-------------------+-------------------------------+

• undrop table

mysql> undrop table t4;
Query OK, 0 rows affected (0.05 sec)
Read 0 rows, 0.00 B in 0.023 sec., 0 rows/sec., 0.00 B/sec.

mysql> show tables;
+-------------------+
| Tables_in_default |
+-------------------+
| t4                |
+-------------------+
2 rows in set (0.07 sec)
Read 98 rows, 14.07 KiB in 0.044 sec., 2.22 thousand rows/sec., 318.62 KiB/sec.

mysql> show tables history like 't4';
+-------------------+-----------+
| Tables_in_default | drop_time |
+-------------------+-----------+
| t4                | NULL      |
+-------------------+-----------+
1 row in set (0.07 sec)
Read 98 rows, 14.07 KiB in 0.044 sec., 2.25 thousand rows/sec., 322.68 KiB/sec.

NOTE:

1. during checking the quota max_tables_per_database, historical dropped tables are NOT counted
2. There is no dedicate privilege for the undrop operation, UserPrivilegeType::Drop is used
3. schema changes of system tables: @flaneur2020
   • An extra column dropped_on is added to system.tables
   • An extra column drop_time is added to information_schema.tables
4. only the legacy parser recognize these new statements @andylokandy
   test case test_statements_in_legacy_suites of common/ast/tests/it/parser.rs been tweaked accordingly
5. drop table no longer delete data @wubx @BohuTANG
   please use truncate table & optimize table purge instead
6. Non fuse tables, could also be undropped, which may not be reasonable.

Changelog

• New Feature
• Not for changelog (changelog entry is not required)

Related Issues

Fixes #5561

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1 Ignored Deployment

Name	Status	Preview	Updated
databend	⬜️ Ignored (Inspect)		May 25, 2022 at 10:48AM (UTC)

[mergify]

Thanks for the contribution!
I have applied any labels matching special text in your PR Changelog.

Please review the labels and make any necessary changes.

[BohuTANG]

cc @flaneur2020

[BohuTANG]

Added pr-need-doc label, cc @soyeric128

[soyeric128]

Hi @dantengsky and @BohuTANG ,

Could you pls confirm if the commands UNDROP and SHOW TABLES HISTORY work with a policy like Data Retention Period? That means only dropped tables still within the retention period can be restored or displayed. If so, please provide more information about the retention policy. Thanks.

[BohuTANG]

Hi, @soyeric128

I think we don't have the retention policy yet. We only have the UNDROP statement.
We can wait a few times for that feature to be finished, let's document them then.

Let's ignore this PR to document for now.

[dantengsky]

Hi @dantengsky and @BohuTANG ,

Could you pls confirm if the commands UNDROP and SHOW TABLES HISTORY work with a policy like Data
...

@soyeric128

Sorry, missed your question totally...
we do not have the whole retention policy yet,

• SHOW TABLES HISTORY now respect the retention time settings
  since the underlying kv API adjusted accordingly Feature: get_{db|table}_history ignore the data out of retention date #5597
• UNDROP seems have not checked the retention/failsafe policy
  not 100% percent sure. @lichuang may have other comments

[BohuTANG]

I have updated the UNDROP TABLE to databend.rs:
https://databend.rs/doc/reference/sql/ddl/table/ddl-undrop-table

cc @soyeric128

[soyeric128]

Hi @dantengsky and @BohuTANG ,
Could you pls confirm if the commands UNDROP and SHOW TABLES HISTORY work with a policy like Data
...

@soyeric128

Sorry, missed your question totally... we do not have the whole retention policy yet,

• SHOW TABLES HISTORY now respect the retention time settings
  since the underlying kv API adjusted accordingly Feature: get_{db|table}_history ignore the data out of retention date #5597
• UNDROP seems have not checked the retention/failsafe policy
  not 100% percent sure. @lichuang may have other comments

Thanks for the reply, @dantengsky. Please let me know when the retention policy is ready, then we can start the document updating. Thank you.

[soyeric128]

I have updated the UNDROP TABLE to databend.rs: https://databend.rs/doc/reference/sql/ddl/table/ddl-undrop-table

cc @soyeric128

Thanks for the updates. Can we update the description a little bit to be more precise?

Restores the recent version of a dropped table. -> Restore the most recent version of a dropped table.