065bea1587
Summary: This is part of an alternative approach to https://github.com/facebook/rocksdb/issues/8316. Unlike that approach, this one relies on key-values getting processed one by one during compaction, and does not involve persistence. Specifically, the patch adds a class `BlobGarbageMeter` that can track the number and total size of blobs in a (sub)compaction's input and output on a per-blob file basis. This information can then be used to compute the amount of additional garbage generated by the compaction for any given blob file by subtracting the "outflow" from the "inflow." Note: this patch only adds `BlobGarbageMeter` and associated unit tests. I plan to hook up this class to the input and output of `CompactionIterator` in a subsequent PR. Pull Request resolved: https://github.com/facebook/rocksdb/pull/8426 Test Plan: `make check` Reviewed By: jay-zhuang Differential Revision: D29242250 Pulled By: ltamasi fbshipit-source-id: 597e50ad556540e413a50e804ba15bc044d809bb