Prefix method

finder.go

@@ -1,6 +1,7 @@
 package storm
 
 import (
+	"fmt"
 	"reflect"
 
 	"github.com/asdine/storm/index"
@@ -29,6 +30,9 @@ type Finder interface {
 	// Range returns one or more records by the specified index within the specified range
 	Range(fieldName string, min, max, to interface{}, options ...func(*index.Options)) error
 
+	// Prefix returns one or more records whose given field starts with the specified prefix.
+	Prefix(fieldName string, prefix string, to interface{}, options ...func(*index.Options)) error
+
 	// Count counts all the records of a bucket
 	Count(data interface{}) (int, error)
 }
@@ -403,6 +407,92 @@ func (n *node) rnge(tx *bolt.Tx, bucketName, fieldName string, cfg *structConfig
 	return sorter.flush()
 }
 
+// Prefix returns one or more records whose given field starts with the specified prefix.
+func (n *node) Prefix(fieldName string, prefix string, to interface{}, options ...func(*index.Options)) error {
+	sink, err := newListSink(n, to)
+	if err != nil {
+		return err
+	}
+
+	bucketName := sink.bucketName()
+	if bucketName == "" {
+		return ErrNoName
+	}
+
+	ref := reflect.Indirect(reflect.New(sink.elemType))
+	cfg, err := extractSingleField(&ref, fieldName)
+	if err != nil {
+		return err
+	}
+
+	opts := index.NewOptions()
+	for _, fn := range options {
+		fn(opts)
+	}
+
+	field, ok := cfg.Fields[fieldName]
+	if !ok || (!field.IsID && field.Index == "") {
+		query := newQuery(n, q.Re(fieldName, fmt.Sprintf("^%s", prefix)))
+		query.Skip(opts.Skip).Limit(opts.Limit)
+
+		if opts.Reverse {
+			query.Reverse()
+		}
+
+		err = n.readTx(func(tx *bolt.Tx) error {
+			return query.query(tx, sink)
+		})
+
+		if err != nil {
+			return err
+		}
+
+		return sink.flush()
+	}
+
+	prfx, err := toBytes(prefix, n.s.codec)
+	if err != nil {
+		return err
+	}
+
+	return n.readTx(func(tx *bolt.Tx) error {
+		return n.prefix(tx, bucketName, fieldName, cfg, sink, prfx, opts)
+	})
+}
+
+func (n *node) prefix(tx *bolt.Tx, bucketName, fieldName string, cfg *structConfig, sink *listSink, prefix []byte, opts *index.Options) error {
+	bucket := n.GetBucket(tx, bucketName)
+	if bucket == nil {
+		reflect.Indirect(sink.ref).SetLen(0)
+		return nil
+	}
+
+	idx, err := getIndex(bucket, cfg.Fields[fieldName].Index, fieldName)
+	if err != nil {
+		return err
+	}
+
+	list, err := idx.Prefix(prefix, opts)
+	if err != nil {
+		return err
+	}
+
+	sink.results = reflect.MakeSlice(reflect.Indirect(sink.ref).Type(), len(list), len(list))
+	sorter := newSorter(n, sink)
+	for i := range list {
+		raw := bucket.Get(list[i])
+		if raw == nil {
+			return ErrNotFound
+		}
+
+		if _, err := sorter.filter(nil, bucket, list[i], raw); err != nil {
+			return err
+		}
+	}
+
+	return sorter.flush()
+}
+
 // Count counts all the records of a bucket
 func (n *node) Count(data interface{}) (int, error) {
 	return n.Select().Count(data)

finder_test.go

@@ -617,3 +617,71 @@ func TestRange(t *testing.T) {
 	require.NoError(t, err)
 	require.Len(t, users, 60)
 }
+
+func TestPrefix(t *testing.T) {
+	db, cleanup := createDB(t)
+	defer cleanup()
+
+	for i := 0; i < 50; i++ {
+		w := User{
+			ID: i + 1,
+		}
+
+		if i%5 == 0 {
+			w.Name = "John"
+			w.Group = "group100"
+		} else {
+			w.Name = "Jack"
+			w.Group = "group200"
+		}
+
+		err := db.Save(&w)
+		require.NoError(t, err)
+	}
+
+	var users []User
+	err := db.Prefix("Name", "Jo", users)
+	require.Equal(t, ErrSlicePtrNeeded, err)
+
+	// Using indexes
+	err = db.Prefix("Name", "Jo", &users)
+	require.NoError(t, err)
+	require.Len(t, users, 10)
+	require.Equal(t, 1, users[0].ID)
+	require.Equal(t, 46, users[9].ID)
+
+	err = db.Prefix("Name", "Ja", &users)
+	require.NoError(t, err)
+	require.Len(t, users, 40)
+	require.Equal(t, 2, users[0].ID)
+	require.Equal(t, 50, users[39].ID)
+
+	err = db.Prefix("Name", "Ja", &users, Limit(10), Skip(20), Reverse())
+	require.NoError(t, err)
+	require.Len(t, users, 10)
+	require.Equal(t, 25, users[0].ID)
+	require.Equal(t, 14, users[9].ID)
+
+	// Using Select
+	err = db.Prefix("Group", "group1", &users)
+	require.NoError(t, err)
+	require.Len(t, users, 10)
+	require.Equal(t, 1, users[0].ID)
+	require.Equal(t, 46, users[9].ID)
+
+	err = db.Prefix("Group", "group2", &users)
+	require.NoError(t, err)
+	require.Len(t, users, 40)
+	require.Equal(t, 2, users[0].ID)
+	require.Equal(t, 50, users[39].ID)
+
+	err = db.Prefix("Group", "group2", &users, Limit(10), Skip(20), Reverse())
+	require.NoError(t, err)
+	require.Len(t, users, 10)
+	require.Equal(t, 25, users[0].ID)
+	require.Equal(t, 14, users[9].ID)
+
+	// Bad value
+	err = db.Prefix("Group", "group3", &users)
+	require.Equal(t, ErrNotFound, err)
+}

index/indexes.go

@@ -10,4 +10,5 @@ type Index interface {
 	All(value []byte, opts *Options) ([][]byte, error)
 	AllRecords(opts *Options) ([][]byte, error)
 	Range(min []byte, max []byte, opts *Options) ([][]byte, error)
+	Prefix(prefix []byte, opts *Options) ([][]byte, error)
 }

storm.go

@@ -187,6 +187,11 @@ func (s *DB) Range(fieldName string, min, max, to interface{}, options ...func(*
 	return s.root.Range(fieldName, min, max, to, options...)
 }
 
+// Prefix returns one or more records whose given field starts with the specified prefix.
+func (s *DB) Prefix(fieldName string, prefix string, to interface{}, options ...func(*index.Options)) error {
+	return s.root.Prefix(fieldName, prefix, to, options...)
+}
+
 // AllByIndex gets all the records of a bucket that are indexed in the specified index
 func (s *DB) AllByIndex(fieldName string, to interface{}, options ...func(*index.Options)) error {
 	return s.root.AllByIndex(fieldName, to, options...)