term field reader supports optionally omitting 3 details

at the time you create the term field reader, you can specify
that you don't need the term freq, the norm, or the term vectors

in that case, the index implementation can choose to not return
them in its subsequently returned values

this is advisory only, some simple implementations may ignore this
and continue to return the values anyway (as the current impl of
upside_down does today)

this change will allow future index implementations the
opportunity to do less work when it isn't required

index/index.go

@@ -60,7 +60,7 @@ type AsyncIndex interface {
 }
 
 type IndexReader interface {
-	TermFieldReader(term []byte, field string) (TermFieldReader, error)
+	TermFieldReader(term []byte, field string, includeFreq, includeNorm, includeTermVectors bool) (TermFieldReader, error)
 
 	// DocIDReader returns an iterator over documents which identifiers are
 	// greater than or equal to start and smaller than end. Set start to the

index/upside_down/index_reader.go

@@ -23,12 +23,12 @@ type IndexReader struct {
 	docCount uint64
 }
 
-func (i *IndexReader) TermFieldReader(term []byte, fieldName string) (index.TermFieldReader, error) {
+func (i *IndexReader) TermFieldReader(term []byte, fieldName string, includeFreq, includeNorm, includeTermVectors bool) (index.TermFieldReader, error) {
 	fieldIndex, fieldExists := i.index.fieldCache.FieldNamed(fieldName, false)
 	if fieldExists {
-		return newUpsideDownCouchTermFieldReader(i, term, uint16(fieldIndex))
+		return newUpsideDownCouchTermFieldReader(i, term, uint16(fieldIndex), includeFreq, includeNorm, includeTermVectors)
 	}
-	return newUpsideDownCouchTermFieldReader(i, []byte{ByteSeparator}, ^uint16(0))
+	return newUpsideDownCouchTermFieldReader(i, []byte{ByteSeparator}, ^uint16(0), includeFreq, includeNorm, includeTermVectors)
 }
 
 func (i *IndexReader) FieldDict(fieldName string) (index.FieldDict, error) {

index/upside_down/reader.go

@@ -25,7 +25,7 @@ type UpsideDownCouchTermFieldReader struct {
 	field       uint16
 }
 
-func newUpsideDownCouchTermFieldReader(indexReader *IndexReader, term []byte, field uint16) (*UpsideDownCouchTermFieldReader, error) {
+func newUpsideDownCouchTermFieldReader(indexReader *IndexReader, term []byte, field uint16, includeFreq, includeNorm, includeTermVectors bool) (*UpsideDownCouchTermFieldReader, error) {
 	dictionaryRow := NewDictionaryRow(term, field, 0)
 	val, err := indexReader.kvreader.Get(dictionaryRow.Key())
 	if err != nil {

index/upside_down/reader_test.go

@@ -72,7 +72,7 @@ func TestIndexReader(t *testing.T) {
 	}()
 
 	// first look for a term that doesn't exist
-	reader, err := indexReader.TermFieldReader([]byte("nope"), "name")
+	reader, err := indexReader.TermFieldReader([]byte("nope"), "name", true, true, true)
 	if err != nil {
 		t.Errorf("Error accessing term field reader: %v", err)
 	}
@@ -85,7 +85,7 @@ func TestIndexReader(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	reader, err = indexReader.TermFieldReader([]byte("test"), "name")
+	reader, err = indexReader.TermFieldReader([]byte("test"), "name", true, true, true)
 	if err != nil {
 		t.Errorf("Error accessing term field reader: %v", err)
 	}
@@ -123,7 +123,7 @@ func TestIndexReader(t *testing.T) {
 			},
 		},
 	}
-	tfr, err := indexReader.TermFieldReader([]byte("rice"), "desc")
+	tfr, err := indexReader.TermFieldReader([]byte("rice"), "desc", true, true, true)
 	if err != nil {
 		t.Errorf("unexpected error: %v", err)
 	}
@@ -140,7 +140,7 @@ func TestIndexReader(t *testing.T) {
 	}
 
 	// now test usage of advance
-	reader, err = indexReader.TermFieldReader([]byte("test"), "name")
+	reader, err = indexReader.TermFieldReader([]byte("test"), "name", true, true, true)
 	if err != nil {
 		t.Errorf("Error accessing term field reader: %v", err)
 	}
@@ -168,7 +168,7 @@ func TestIndexReader(t *testing.T) {
 	}
 
 	// now test creating a reader for a field that doesn't exist
-	reader, err = indexReader.TermFieldReader([]byte("water"), "doesnotexist")
+	reader, err = indexReader.TermFieldReader([]byte("water"), "doesnotexist", true, true, true)
 	if err != nil {
 		t.Errorf("Error accessing term field reader: %v", err)
 	}

index/upside_down/upside_down_test.go

@@ -1119,7 +1119,7 @@ func TestIndexTermReaderCompositeFields(t *testing.T) {
 		}
 	}()
 
-	termFieldReader, err := indexReader.TermFieldReader([]byte("mister"), "_all")
+	termFieldReader, err := indexReader.TermFieldReader([]byte("mister"), "_all", true, true, true)
 	if err != nil {
 		t.Error(err)
 	}

search/searchers/search_term.go

@@ -26,7 +26,7 @@ type TermSearcher struct {
 }
 
 func NewTermSearcher(indexReader index.IndexReader, term string, field string, boost float64, explain bool) (*TermSearcher, error) {
-	reader, err := indexReader.TermFieldReader([]byte(term), field)
+	reader, err := indexReader.TermFieldReader([]byte(term), field, true, true, true)
 	if err != nil {
 		return nil, err
 	}