fix(core): change delete-on-updates to remove-on-update and set default false

dgraph/cmd/alpha/run.go

@@ -134,12 +134,15 @@ they form a Raft group and provide synchronous replication.
 		Flag("percentage",
 			"Cache percentages summing up to 100 for various caches (FORMAT: PostingListCache,"+
 				"PstoreBlockCache,PstoreIndexCache)").
-		Flag("delete-on-updates",
-			"When set as true, we would delete the key from the cache once it's updated. If it's not "+
-				"we would update the value inside the cache. If the cache gets too full, it starts"+
-				" to get slow. So if your usecase has a lot of heavy mutations, this should be set"+
-				" as true. If you are modifying same data again and again, this should be set as"+
-				" false").
+		Flag("remove-on-update",
+			"Dgraph implements a read-through cache (using Ristretto) to optimize query performance. On "+
+				"mutation, the new value is first written to disk and then updated in the cache "+
+				"before the transaction completes to ensure there are no stale reads during parallel "+
+				"transactions. In mutation-heavy use cases, it may be more advantageous to remove "+
+				"the cache entry on mutation instead of updating the value, as this executes ~14\\%"+
+				"faster on write. The new value will be added to the cache the first time it is "+
+				"queried, slightly delaying that read. To use this approach, set the --cache "+
+				"remove-on-update flag.").
 		String())
 
 	flag.String("raft", worker.RaftDefaults, z.NewSuperFlagHelp(worker.RaftDefaults).
@@ -628,7 +631,7 @@ func run() {
 	x.AssertTruef(totalCache >= 0, "ERROR: Cache size must be non-negative")
 
 	cachePercentage := cache.GetString("percentage")
-	deleteOnUpdates := cache.GetBool("delete-on-updates")
+	removeOnUpdate := cache.GetBool("remove-on-update")
 	cachePercent, err := x.GetCachePercentages(cachePercentage, 3)
 	x.Check(err)
 	postingListCacheSize := (cachePercent[0] * (totalCache << 20)) / 100
@@ -651,7 +654,7 @@ func run() {
 		WALDir:          Alpha.Conf.GetString("wal"),
 		CacheMb:         totalCache,
 		CachePercentage: cachePercentage,
-		DeleteOnUpdates: deleteOnUpdates,
+		RemoveOnUpdate:  removeOnUpdate,
 
 		MutationsMode:      worker.AllowMutations,
 		AuthToken:          security.GetString("token"),
@@ -779,7 +782,7 @@ func run() {
 	// Posting will initialize index which requires schema. Hence, initialize
 	// schema before calling posting.Init().
 	schema.Init(worker.State.Pstore)
-	posting.Init(worker.State.Pstore, postingListCacheSize, deleteOnUpdates)
+	posting.Init(worker.State.Pstore, postingListCacheSize, removeOnUpdate)
 	defer posting.Cleanup()
 	worker.Init(worker.State.Pstore)
 

posting/lists.go

@@ -33,12 +33,12 @@ var (
 )
 
 // Init initializes the posting lists package, the in memory and dirty list hash.
-func Init(ps *badger.DB, cacheSize int64, deleteOnUpdates bool) {
+func Init(ps *badger.DB, cacheSize int64, removeOnUpdate bool) {
 	pstore = ps
 	closer = z.NewCloser(1)
 	go x.MonitorMemoryMetrics(closer)
 
-	memoryLayer = initMemoryLayer(cacheSize, deleteOnUpdates)
+	memoryLayer = initMemoryLayer(cacheSize, removeOnUpdate)
 }
 
 func UpdateMaxCost(maxCost int64) {

posting/mvcc.go

@@ -390,7 +390,7 @@ func (c *Cache) clear() {
 
 type MemoryLayer struct {
 	// config
-	deleteOnUpdates bool
+	removeOnUpdate bool
 
 	// data
 	cache *Cache
@@ -410,9 +410,9 @@ func GetStatsHolder() *StatsHolder {
 	return memoryLayer.statsHolder
 }
 
-func initMemoryLayer(cacheSize int64, deleteOnUpdates bool) *MemoryLayer {
+func initMemoryLayer(cacheSize int64, removeOnUpdate bool) *MemoryLayer {
 	ml := &MemoryLayer{}
-	ml.deleteOnUpdates = deleteOnUpdates
+	ml.removeOnUpdate = removeOnUpdate
 	ml.statsHolder = NewStatsHolder()
 	if cacheSize > 0 {
 		cache, err := ristretto.NewCache[[]byte, *CachePL](&ristretto.Config[[]byte, *CachePL]{
@@ -476,7 +476,7 @@ func (ml *MemoryLayer) updateItemInCache(key string, delta []byte, startTs, comm
 		return
 	}
 
-	if ml.deleteOnUpdates {
+	if ml.removeOnUpdate {
 		// TODO We should mark the key as deleted instead of directly deleting from the cache.
 		ml.del([]byte(key))
 		return

worker/config.go

@@ -52,11 +52,11 @@ type Options struct {
 	CachePercentage string
 	// CacheMb is the total memory allocated between all the caches.
 	CacheMb int64
-	// DeleteOnUpdates is the parameter that allows the user to set if the cache should keep the items that were
+	// RemoveOnUpdate is the parameter that allows the user to set if the cache should keep the items that were
 	// just mutated. Keeping these items are good when there is a mixed workload where you are updating the
 	// same element multiple times. However, for a heavy mutation workload, not keeping these items would be better
 	// , as keeping these elements bloats the cache making it slow.
-	DeleteOnUpdates bool
+	RemoveOnUpdate bool
 
 	Audit *x.LoggerConf
 

worker/server_state.go

@@ -41,7 +41,7 @@ const (
 	ZeroLimitsDefaults = `uid-lease=0; refill-interval=30s; disable-admin-http=false;`
 	GraphQLDefaults    = `introspection=true; debug=false; extensions=true; poll-interval=1s; ` +
 		`lambda-url=;`
-	CacheDefaults        = `size-mb=1024; percentage=40,40,20; delete-on-updates=true`
+	CacheDefaults        = `size-mb=1024; percentage=40,40,20; remove-on-update=false`
 	FeatureFlagsDefaults = `normalize-compatibility-mode=`
 )