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

Users Badger
1

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?

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package main

import (
	"fmt"
	"log"
	"time"

	"github.com/dgraph-io/badger/v3"
)

func main() {
	// Open the Badger database
	opts := badger.DefaultOptions("").WithInMemory(true)
	db, err := badger.Open(opts)
	if err != nil {
		log.Fatal(err)
	}
	defer db.Close()

	// Run a ticker to periodically check the size and run GC
	ticker := time.NewTicker(10 * time.Second)
	defer ticker.Stop()

	for range ticker.C {
		lsmSize, vlogSize := db.Size()

		fmt.Printf("LSM Size: %d bytes, Vlog Size: %d bytes\n", lsmSize, vlogSize)

		// Define a threshold for when to run GC
		const gcThreshold int64 = 100 * 1024 * 1024 // 100 MB

		if vlogSize > gcThreshold {
			fmt.Println("Running value log GC...")
			err := db.RunValueLogGC(0.5) // 0.5 is the discard ratio
			if err != nil {
				if err != badger.ErrNoRewrite {
					log.Printf("Error running GC: %v\n", err)
				}
			} else {
				fmt.Println("GC completed successfully")
			}
		}
	}
}```