Merge pull request #466 from steveyen/optimize-fieldDict-reader-with-prealloc

Optimize upside-down's field dict reader with preallocated objects

index/upsidedown/field_dict.go

@@ -24,6 +24,8 @@ import (
 type UpsideDownCouchFieldDict struct {
 	indexReader *IndexReader
 	iterator    store.KVIterator
+	dictRow     *DictionaryRow
+	dictEntry   *index.DictEntry
 	field       uint16
 }
 
@@ -42,6 +44,8 @@ func newUpsideDownCouchFieldDict(indexReader *IndexReader, field uint16, startTe
 	return &UpsideDownCouchFieldDict{
 		indexReader: indexReader,
 		iterator:    it,
+		dictRow:     &DictionaryRow{},   // Pre-alloced, reused row.
+		dictEntry:   &index.DictEntry{}, // Pre-alloced, reused entry.
 		field:       field,
 	}, nil
 
@@ -53,17 +57,19 @@ func (r *UpsideDownCouchFieldDict) Next() (*index.DictEntry, error) {
 		return nil, nil
 	}
 
-	currRow, err := NewDictionaryRowKV(key, val)
+	err := r.dictRow.parseDictionaryK(key)
 	if err != nil {
-		return nil, fmt.Errorf("unexpected error parsing dictionary row kv: %v", err)
+		return nil, fmt.Errorf("unexpected error parsing dictionary row key: %v", err)
 	}
-	rv := index.DictEntry{
-		Term:  string(currRow.term),
-		Count: currRow.count,
+	err = r.dictRow.parseDictionaryV(val)
+	if err != nil {
+		return nil, fmt.Errorf("unexpected error parsing dictionary row val: %v", err)
 	}
+	r.dictEntry.Term = string(r.dictRow.term)
+	r.dictEntry.Count = r.dictRow.count
 	// advance the iterator to the next term
 	r.iterator.Next()
-	return &rv, nil
+	return r.dictEntry, nil
 
 }
 

index/upsidedown/row.go

@@ -242,9 +242,9 @@ func NewFieldRowKV(key, value []byte) (*FieldRow, error) {
 const DictionaryRowMaxValueSize = binary.MaxVarintLen64
 
 type DictionaryRow struct {
-	field uint16
 	term  []byte
 	count uint64
+	field uint16
 }
 
 func (dr *DictionaryRow) Key() []byte {
@@ -306,36 +306,29 @@ func NewDictionaryRowKV(key, value []byte) (*DictionaryRow, error) {
 }
 
 func NewDictionaryRowK(key []byte) (*DictionaryRow, error) {
-	rv := DictionaryRow{}
-	buf := bytes.NewBuffer(key)
-	_, err := buf.ReadByte() // type
+	rv := &DictionaryRow{}
+	err := rv.parseDictionaryK(key)
 	if err != nil {
 		return nil, err
 	}
+	return rv, nil
+}
 
-	err = binary.Read(buf, binary.LittleEndian, &rv.field)
-	if err != nil {
-		return nil, err
+func (dr *DictionaryRow) parseDictionaryK(key []byte) error {
+	dr.field = binary.LittleEndian.Uint16(key[1:3])
+	if dr.term != nil {
+		dr.term = dr.term[:0]
 	}
-
-	rv.term, err = buf.ReadBytes(ByteSeparator)
-	// there is no separator expected here, should get EOF
-	if err != io.EOF {
-		return nil, err
-	}
-
-	return &rv, nil
+	dr.term = append(dr.term, key[3:]...)
+	return nil
 }
 
 func (dr *DictionaryRow) parseDictionaryV(value []byte) error {
-	buf := bytes.NewBuffer(value)
-
-	count, err := binary.ReadUvarint(buf)
-	if err != nil {
-		return err
+	count, nread := binary.Uvarint(value)
+	if nread <= 0 {
+		return fmt.Errorf("DictionaryRow parse Uvarint error, nread: %d", nread)
 	}
 	dr.count = count
-
 	return nil
 }