Tables in MergeTree Family Gain Virtual Column _partition_id

Why it matters

This feature introduces the virtual column _partition_id to allow users to easily access the partition identifier directly from MergeTree tables. It simplifies queries that require partition-related information without needing to extract or compute it manually.

How to use it

Users can directly query the _partition_id column in their SELECT statements from any MergeTree family table to retrieve the partition identifier, for example:

SELECT _partition_id, COUNT(*) FROM my_mergetree_table GROUP BY _partition_id