v.21.1Improvements

Temporary Tables Visibility in ClickHouse System Tables Updated

Official CH changelog text
Temporary tables are visible in the system tables system.tables and system.columns now only in those session where they have been created. The internal database _temporary_and_external_tables is now hidden in those system tables; temporary tables are shown as tables with empty database with the is_temporary flag set instead. #18014 (Vitaly Baranov).
Temporary tables are now visible in system.tables and system.columns only within the session they were created, with the internal database _temporary_and_external_tables hidden. Temporary tables appear with an empty database name and an is_temporary flag set.

Why it matters

This feature enhances the visibility and isolation of temporary tables by ensuring they are only shown in the system tables for their creating session, preventing confusion and potential conflicts across sessions. It improves system table clarity by hiding the internal database used for temporary and external tables and provides a clear flag to identify temporary tables.

How to use it

No specific action is needed to enable this feature. Once updated, users will see temporary tables only in their creating session within system.tables and system.columns, represented with an empty database name and the is_temporary flag set.

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