Support BACKUP ALL command

[vitlibar]

Changelog category:

• Improvement

Changelog entry:

Added support for BACKUP ALL command which backups all tables and databases, including temporary and system ones.

[nikitamikhaylov]

@vitlibar This is something we have to address

E           Exception: ClickHouse HTTP server returned 500 Internal Server Error: Code: 608. DB::Exception: Cannot restore the table system.asynchronous_metric_log because it already contains some data. You can set structure_only=true or allow_non_empty_tables=true to overcome that in the way you want: While restoring data of table system.asynchronous_metric_log. (CANNOT_RESTORE_TABLE) (version 23.3.1.1)

Because almost all tables with _log suffix will always contain some data even on a fresh instance.

[vitlibar]

Because almost all tables with _log suffix will always contain some data even on a fresh instance.

I can set allow_non_empty_tables=true for that test to make RESTORE just merge the contents of those tables (that will cause row duplication in those log tables, but I think it's ok for the test).

Or as an alternative way I can exclude those tables from the backup with

BACKUP ALL EXCEPT TABLE system.asynchronous_metric_log, ...

I think both ways are worth to be tested