pool: support CountMany() using hyperloglog.

envelopes.go

@@ -2,6 +2,7 @@ package nostr
 
 import (
 	"bytes"
+	"encoding/hex"
 	"encoding/json"
 	"fmt"
 	"strconv"
@@ -142,7 +143,8 @@ func (v ReqEnvelope) MarshalJSON() ([]byte, error) {
 type CountEnvelope struct {
 	SubscriptionID string
 	Filters
-	Count *int64
+	Count       *int64
+	HyperLogLog []byte
 }
 
 func (_ CountEnvelope) Label() string { return "COUNT" }
@@ -161,9 +163,11 @@ func (v *CountEnvelope) UnmarshalJSON(data []byte) error {
 
 	var countResult struct {
 		Count *int64 `json:"count"`
+		HLL   string `json:"hll"`
 	}
 	if err := json.Unmarshal([]byte(arr[2].Raw), &countResult); err == nil && countResult.Count != nil {
 		v.Count = countResult.Count
+		v.HyperLogLog, _ = hex.DecodeString(countResult.HLL)
 		return nil
 	}
 
@@ -189,6 +193,13 @@ func (v CountEnvelope) MarshalJSON() ([]byte, error) {
 	if v.Count != nil {
 		w.RawString(`,{"count":`)
 		w.RawString(strconv.FormatInt(*v.Count, 10))
+		if v.HyperLogLog != nil {
+			w.RawString(`,"hll":"`)
+			hllHex := make([]byte, 0, 512)
+			hex.Encode(hllHex, v.HyperLogLog)
+			w.Buffer.AppendBytes(hllHex)
+			w.RawString(`"`)
+		}
 		w.RawString(`}`)
 	} else {
 		for _, filter := range v.Filters {

nip45/helpers.go → nip45/hyperloglog/helpers.go

@@ -1,4 +1,4 @@
-package nip45
+package hyperloglog
 
 import (
 	"math"

nip45/hll.go → nip45/hyperloglog/hll.go

@@ -1,4 +1,4 @@
-package nip45
+package hyperloglog
 
 import (
 	"encoding/binary"
@@ -18,13 +18,14 @@ func New() *HyperLogLog {
 	return hll
 }
 
-func (hll *HyperLogLog) Encode() string {
-	return hex.EncodeToString(hll.registers)
-}
-
-func (hll *HyperLogLog) Decode(enc string) error {
-	_, err := hex.Decode(hll.registers, []byte(enc))
-	return err
+func (hll *HyperLogLog) GetRegisters() []byte    { return hll.registers }
+func (hll *HyperLogLog) SetRegisters(enc []byte) { hll.registers = enc }
+func (hll *HyperLogLog) MergeRegisters(other []byte) {
+	for i, v := range other {
+		if v > hll.registers[i] {
+			hll.registers[i] = v
+		}
+	}
 }
 
 func (hll *HyperLogLog) Clear() {
@@ -45,13 +46,12 @@ func (hll *HyperLogLog) Add(id string) {
 	}
 }
 
-func (hll *HyperLogLog) Merge(other *HyperLogLog) error {
+func (hll *HyperLogLog) Merge(other *HyperLogLog) {
 	for i, v := range other.registers {
 		if v > hll.registers[i] {
 			hll.registers[i] = v
 		}
 	}
-	return nil
 }
 
 func (hll *HyperLogLog) Count() uint64 {

nip45/hll_test.go → nip45/hyperloglog/hll_test.go

@@ -1,4 +1,4 @@
-package nip45
+package hyperloglog
 
 import (
 	"encoding/hex"

pool.go

@@ -10,6 +10,7 @@ import (
 	"sync"
 	"time"
 
+	"github.com/nbd-wtf/go-nostr/nip45/hyperloglog"
 	"github.com/puzpuzpuz/xsync/v3"
 )
 
@@ -468,6 +469,39 @@ func (pool *SimplePool) subManyEose(
 	return events
 }
 
+// CountMany aggregates count results from multiple relays using HyperLogLog
+func (pool *SimplePool) CountMany(
+	ctx context.Context,
+	urls []string,
+	filter Filter,
+	opts []SubscriptionOption,
+) int {
+	hll := hyperloglog.New()
+
+	wg := sync.WaitGroup{}
+	wg.Add(len(urls))
+	for _, url := range urls {
+		go func(nm string) {
+			defer wg.Done()
+			relay, err := pool.EnsureRelay(url)
+			if err != nil {
+				return
+			}
+			ce, err := relay.countInternal(ctx, Filters{filter}, opts...)
+			if err != nil {
+				return
+			}
+			if len(ce.HyperLogLog) != 256 {
+				return
+			}
+			hll.MergeRegisters(ce.HyperLogLog)
+		}(NormalizeURL(url))
+	}
+
+	wg.Wait()
+	return int(hll.Count())
+}
+
 // QuerySingle returns the first event returned by the first relay, cancels everything else.
 func (pool *SimplePool) QuerySingle(ctx context.Context, urls []string, filter Filter) *RelayEvent {
 	ctx, cancel := context.WithCancel(ctx)

relay.go

@@ -273,7 +273,7 @@ func (r *Relay) ConnectWithTLS(ctx context.Context, tlsConfig *tls.Config) error
 				}
 			case *CountEnvelope:
 				if subscription, ok := r.Subscriptions.Load(subIdToSerial(env.SubscriptionID)); ok && env.Count != nil && subscription.countResult != nil {
-					subscription.countResult <- *env.Count
+					subscription.countResult <- *env
 				}
 			case *OKEnvelope:
 				if okCallback, exist := r.okCallbacks.Load(env.EventID); exist {
@@ -478,11 +478,19 @@ func (r *Relay) QuerySync(ctx context.Context, filter Filter) ([]*Event, error)
 }
 
 func (r *Relay) Count(ctx context.Context, filters Filters, opts ...SubscriptionOption) (int64, error) {
+	v, err := r.countInternal(ctx, filters, opts...)
+	if err != nil {
+		return 0, err
+	}
+	return *v.Count, nil
+}
+
+func (r *Relay) countInternal(ctx context.Context, filters Filters, opts ...SubscriptionOption) (CountEnvelope, error) {
 	sub := r.PrepareSubscription(ctx, filters, opts...)
-	sub.countResult = make(chan int64)
+	sub.countResult = make(chan CountEnvelope)
 
 	if err := sub.Fire(); err != nil {
-		return 0, err
+		return CountEnvelope{}, err
 	}
 
 	defer sub.Unsub()
@@ -499,7 +507,7 @@ func (r *Relay) Count(ctx context.Context, filters Filters, opts ...Subscription
 		case count := <-sub.countResult:
 			return count, nil
 		case <-ctx.Done():
-			return 0, ctx.Err()
+			return CountEnvelope{}, ctx.Err()
 		}
 	}
 }

subscription.go

@@ -15,7 +15,7 @@ type Subscription struct {
 	Filters Filters
 
 	// for this to be treated as a COUNT and not a REQ this must be set
-	countResult chan int64
+	countResult chan CountEnvelope
 
 	// the Events channel emits all EVENTs that come in a Subscription
 	// will be closed when the subscription ends
@@ -152,7 +152,7 @@ func (sub *Subscription) Fire() error {
 	if sub.countResult == nil {
 		reqb, _ = ReqEnvelope{sub.id, sub.Filters}.MarshalJSON()
 	} else {
-		reqb, _ = CountEnvelope{sub.id, sub.Filters, nil}.MarshalJSON()
+		reqb, _ = CountEnvelope{sub.id, sub.Filters, nil, nil}.MarshalJSON()
 	}
 
 	sub.live.Store(true)