How db.Size function helps to decide how often to do GC

rohanil · August 12, 2019, 8:47am

db.Size() function returns lsm, vlog file’s sizes. Its comment says It can be used to decide how often to call RunValueLogGC. How lsm and vlog file sizes will tell how often to do GC?

github.com

dgraph-io/badger/blob/74ed6da2c776a6b4941596df9da3ff84a0703c70/db.go#L1081


	if len(val.Value) > 0 {
		head.Decode(val.Value)
	}

	// Pick a log file and run GC
	return db.vlog.runGC(discardRatio, head)
}

// Size returns the size of lsm and value log files in bytes. It can be used to decide how often to
// call RunValueLogGC.
func (db *DB) Size() (lsm, vlog int64) {
	if y.LSMSize.Get(db.opt.Dir) == nil {
		lsm, vlog = 0, 0
		return
	}
	lsm = y.LSMSize.Get(db.opt.Dir).(*expvar.Int).Value()
	vlog = y.VlogSize.Get(db.opt.ValueDir).(*expvar.Int).Value()
	return
}

// Sequence represents a Badger sequence.

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How db.Size function helps to decide how often to do GC

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