# Important Metrics

+ `GC in Compaction Filter`
  + `filtered`: Keys fitered out during compaction
  + `rollback/lock`: Rollback and lock records filtered out during compaction (included in "filtered")
    + The rollback and lock records are special records generated during transaction rolling backs and **`SELECT ... FOR UPDATE`**
    + They don't represent any data
![`smart`](GCInCompactionFilter_aa_001_20221026.png)

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