Introduction of system.completions table

Why it matters

The system.completions table provides users with query autocomplete suggestions and metadata about available completions. This feature enhances the user experience by enabling better interactive query writing and assistance within ClickHouse environments.

How to use it

Users can query the new system.completions table directly using SELECT statements to retrieve information about possible completions. For example:

SELECT * FROM system.completions WHERE ...

This table is available by default after upgrading to the new ClickHouse version supporting this feature.