v.21.6Improvement
Add _partition_value Virtual Column to MergeTree for Deterministic Partition Pruning
Add _partition_value virtual column to MergeTree table family. It can be used to prune partition in a deterministic way. It's needed to implement partition matcher for mutations. #23673 (Amos Bird).Why it matters
Solve partition pruning challenges and enable more efficient mutation operations. The_partition_value virtual column provides a reliable way to reference and match partitions, which is especially useful when implementing partition matchers for mutations.How to use it
Users can reference the_partition_value virtual column directly in queries on MergeTree tables to filter or prune partitions. For example, include _partition_value in the WHERE clause to limit the query scope deterministically by partition.