Refresh iterator in DisconnectBlocks to avoid huge snapshot

db/rocksdb.go

@@ -416,14 +416,23 @@ func (d *RocksDB) DisconnectBlocks(
 	higher uint32,
 ) error {
 	glog.Infof("rocksdb: disconnecting blocks %d-%d", lower, higher)
-	it := d.db.NewIteratorCF(d.ro, d.cfh[cfOutputs])
-	defer it.Close()
 	outputKeys := [][]byte{}
 	outputValues := [][]byte{}
-	var totalOutputs uint64
+	var totalOutputs, count uint64
-	for it.SeekToFirst(); it.Valid(); it.Next() {
+	var seekKey []byte
+	for {
+		var key []byte
+		it := d.db.NewIteratorCF(d.ro, d.cfh[cfOutputs])
+		if totalOutputs == 0 {
+			it.SeekToFirst()
+		} else {
+			it.Seek(seekKey)
+			it.Next()
+		}
+		for count = 0; it.Valid() && count < 1000000; it.Next() {
 			totalOutputs++
-		key := it.Key().Data()
+			count++
+			key = it.Key().Data()
 			l := len(key)
 			if l > 4 {
 				height := unpackUint(key[l-4 : l])
@@ -438,6 +447,14 @@ func (d *RocksDB) DisconnectBlocks(
 				}
 			}
 		}
+		seekKey = make([]byte, len(key))
+		copy(seekKey, key)
+		valid := it.Valid()
+		it.Close()
+		if !valid {
+			break
+		}
+	}
 	glog.Infof("rocksdb: about to disconnect %d outputs from %d", len(outputKeys), totalOutputs)
 	wb := gorocksdb.NewWriteBatch()
 	defer wb.Destroy()