pageserver: filter out the keys from parent shard but not belong to this shard when create delta layer

[gripleaf]

When use CompactionAlgorithm::Tiered to compact, and executing the CompactionStrategy::CreateDelta job, pageserver do not filter out the keys which from parent shard layer but not belong to this shard.

When create image, pageserver would filter out above keys.

code-create_delta

Is this code logic by design?

[jcsp]

This is not by design. The Tiered compaction code was written around the same time that shard splitting was implemented, so they raced.

We are not currently using CompactionAlgorithm::Tiered for our production service, it should be regarded as experimental.