prevent saving duplicates in badger and lmdb.

badger/delete.go

@@ -25,7 +25,6 @@ func (b *BadgerBackend) DeleteEvent(ctx context.Context, evt *nostr.Event) error
 		it := txn.NewIterator(opts)
 		it.Seek(prefix)
 		if it.ValidForPrefix(prefix) {
-			// the key is the last 32 bytes
 			idx = append(idx, it.Item().Key()[1+32:]...)
 		}
 		it.Close()

badger/save.go

@@ -2,14 +2,31 @@ package badger
 
 import (
 	"context"
+	"encoding/hex"
 
 	"github.com/dgraph-io/badger/v4"
+	"github.com/fiatjaf/eventstore"
 	"github.com/nbd-wtf/go-nostr"
 	nostr_binary "github.com/nbd-wtf/go-nostr/binary"
 )
 
 func (b *BadgerBackend) SaveEvent(ctx context.Context, evt *nostr.Event) error {
 	return b.Update(func(txn *badger.Txn) error {
+		// query event by id to ensure we don't save duplicates
+		id, _ := hex.DecodeString(evt.ID)
+		prefix := make([]byte, 1+32)
+		copy(prefix[1:], id)
+		opts := badger.DefaultIteratorOptions
+		opts.PrefetchValues = false
+		it := txn.NewIterator(opts)
+		defer it.Close()
+		it.Seek(prefix)
+		if it.ValidForPrefix(prefix) {
+			// event exists
+			return eventstore.ErrDupEvent
+		}
+
+		// encode to binary
 		bin, err := nostr_binary.Marshal(evt)
 		if err != nil {
 			return err