Why `partial_merge` not called when `get` is called and there are multiple merge operations?

Hi,

I've encountered a scenario where a get operation is performed after a large number of merge operations, and observed that the number of operators in the merge_operator triggered by the get operation has been incrementing, and only the full_merge callback set at initialization was called.

But according to the wiki description, if there are multiple merge operations when the get operation is executed, it should first call partial_merge to try to merge the operands, so why does this logic only trigger when the compaction is performed (tested)?