updated datastore (Query)

Godeps/Godeps.json

@@ -110,7 +110,7 @@
 		},
 		{
 			"ImportPath": "github.com/jbenet/go-datastore",
-			"Rev": "6a1c83bda2a71a9bdc936749fdb507df958ed949"
+			"Rev": "8a8988d1a4e174274bd4a9dd55c4837f46fdf323"
 		},
 		{
 			"ImportPath": "github.com/jbenet/go-fuse-version",

Godeps/_workspace/src/github.com/jbenet/go-datastore/.travis.yml

@@ -0,0 +1,11 @@
+language: go
+
+go:
+  - 1.3
+  - release
+  - tip
+
+script:
+  - make test
+
+env: TEST_NO_FUSE=1 TEST_VERBOSE=1

Godeps/_workspace/src/github.com/jbenet/go-datastore/Makefile

@@ -1,6 +1,9 @@
 build:
 	go build
 
+test:
+	go test ./...
+
 # saves/vendors third-party dependencies to Godeps/_workspace
 # -r flag rewrites import paths to use the vendored path
 # ./... performs operation on all packages in tree

Godeps/_workspace/src/github.com/jbenet/go-datastore/basic_ds.go

@@ -1,6 +1,10 @@
 package datastore
 
-import "log"
+import (
+	"log"
+
+	query "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore/query"
+)
 
 // Here are some basic datastore implementations.
 
@@ -45,13 +49,15 @@ func (d *MapDatastore) Delete(key Key) (err error) {
 	return nil
 }
 
-// KeyList implements Datastore.KeyList
-func (d *MapDatastore) KeyList() ([]Key, error) {
-	var keys []Key
-	for k := range d.values {
-		keys = append(keys, k)
+// Query implements Datastore.Query
+func (d *MapDatastore) Query(q query.Query) (*query.Results, error) {
+	re := make([]query.Entry, 0, len(d.values))
+	for k, v := range d.values {
+		re = append(re, query.Entry{Key: k.String(), Value: v})
 	}
-	return keys, nil
+	r := query.ResultsWithEntries(q, re)
+	r = q.ApplyTo(r)
+	return r, nil
 }
 
 // NullDatastore stores nothing, but conforms to the API.
@@ -84,9 +90,9 @@ func (d *NullDatastore) Delete(key Key) (err error) {
 	return nil
 }
 
-// KeyList implements Datastore.KeyList
-func (d *NullDatastore) KeyList() ([]Key, error) {
-	return nil, nil
+// Query implements Datastore.Query
+func (d *NullDatastore) Query(q query.Query) (*query.Results, error) {
+	return query.ResultsWithEntries(q, nil), nil
 }
 
 // LogDatastore logs all accesses through the datastore.
@@ -140,8 +146,8 @@ func (d *LogDatastore) Delete(key Key) (err error) {
 	return d.child.Delete(key)
 }
 
-// KeyList implements Datastore.KeyList
-func (d *LogDatastore) KeyList() ([]Key, error) {
-	log.Printf("%s: Get KeyList\n", d.Name)
-	return d.child.KeyList()
+// Query implements Datastore.Query
+func (d *LogDatastore) Query(q query.Query) (*query.Results, error) {
+	log.Printf("%s: Query\n", d.Name)
+	return d.child.Query(q)
 }

Godeps/_workspace/src/github.com/jbenet/go-datastore/datastore.go

@@ -2,6 +2,8 @@ package datastore
 
 import (
 	"errors"
+
+	query "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore/query"
 )
 
 /*
@@ -52,8 +54,19 @@ type Datastore interface {
 	// Delete removes the value for given `key`.
 	Delete(key Key) (err error)
 
-	// KeyList returns a list of keys in the datastore
-	KeyList() ([]Key, error)
+	// Query searches the datastore and returns a query result. This function
+	// may return before the query actually runs. To wait for the query:
+	//
+	//   result, _ := ds.Query(q)
+	//
+	//   // use the channel interface; result may come in at different times
+	//   for entry := range result.Entries() { ... }
+	//
+	//	 // or wait for the query to be completely done
+	//   result.Wait()
+	//   result.AllEntries()
+	//
+	Query(q query.Query) (*query.Results, error)
 }
 
 // ThreadSafeDatastore is an interface that all threadsafe datastore should

Godeps/_workspace/src/github.com/jbenet/go-datastore/elastigo/datastore.go

@@ -8,6 +8,7 @@ import (
 
 	"github.com/codahale/blake2"
 	ds "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore"
+	query "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore/query"
 	"github.com/mattbaird/elastigo/api"
 	"github.com/mattbaird/elastigo/core"
 )
@@ -112,7 +113,7 @@ func (d *Datastore) Delete(key ds.Key) (err error) {
 	return nil
 }
 
-func (d *Datastore) KeyList() ([]ds.Key, error) {
+func (d *Datastore) Query(query.Query) (*query.Results, error) {
 	return nil, errors.New("Not yet implemented!")
 }
 

Godeps/_workspace/src/github.com/jbenet/go-datastore/fs/fs.go

@@ -8,8 +8,11 @@ import (
 	"strings"
 
 	ds "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore"
+	query "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore/query"
 )
 
+var ObjectKeySuffix = ".dsobject"
+
 // Datastore uses a standard Go map for internal storage.
 type Datastore struct {
 	path string
@@ -26,7 +29,7 @@ func NewDatastore(path string) (ds.Datastore, error) {
 
 // KeyFilename returns the filename associated with `key`
 func (d *Datastore) KeyFilename(key ds.Key) string {
-	return filepath.Join(d.path, key.String(), ".dsobject")
+	return filepath.Join(d.path, key.String(), ObjectKeySuffix)
 }
 
 // Put stores the given value.
@@ -79,10 +82,10 @@ func (d *Datastore) Delete(key ds.Key) (err error) {
 	return os.Remove(fn)
 }
 
-// KeyList returns a list of all keys in the datastore
-func (d *Datastore) KeyList() ([]ds.Key, error) {
+// Query implements Datastore.Query
+func (d *Datastore) Query(q query.Query) (*query.Results, error) {
 
-	keys := []ds.Key{}
+	entries := make(chan query.Entry)
 
 	walkFn := func(path string, info os.FileInfo, err error) error {
 		// remove ds path prefix
@@ -91,14 +94,22 @@ func (d *Datastore) KeyList() ([]ds.Key, error) {
 		}
 
 		if !info.IsDir() {
+			if strings.HasSuffix(path, ObjectKeySuffix) {
+				path = path[:len(path)-len(ObjectKeySuffix)]
+			}
 			key := ds.NewKey(path)
-			keys = append(keys, key)
+			entries <- query.Entry{Key: key.String(), Value: query.NotFetched}
 		}
 		return nil
 	}
 
-	filepath.Walk(d.path, walkFn)
-	return keys, nil
+	go func() {
+		filepath.Walk(d.path, walkFn)
+		close(entries)
+	}()
+	r := query.ResultsWithEntriesChan(q, entries)
+	r = q.ApplyTo(r)
+	return r, nil
 }
 
 // isDir returns whether given path is a directory

Godeps/_workspace/src/github.com/jbenet/go-datastore/fs/fs_test.go

@@ -4,9 +4,11 @@ import (
 	"bytes"
 	"testing"
 
+	. "launchpad.net/gocheck"
+
 	ds "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore"
 	fs "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore/fs"
-	. "launchpad.net/gocheck"
+	query "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore/query"
 )
 
 // Hook up gocheck into the "go test" runner.
@@ -54,6 +56,32 @@ func (ks *DSSuite) TestBasic(c *C) {
 		c.Check(err, Equals, nil)
 		c.Check(bytes.Equal(v.([]byte), []byte(k.String())), Equals, true)
 	}
+
+	r, err := ks.ds.Query(query.Query{Prefix: "/foo/bar/"})
+	if err != nil {
+		c.Check(err, Equals, nil)
+	}
+
+	expect := []string{
+		"/foo/bar/baz",
+		"/foo/bar/bazb",
+		"/foo/bar/baz/barb",
+	}
+	all := r.AllEntries()
+	c.Check(len(all), Equals, len(expect))
+
+	for _, k := range expect {
+		found := false
+		for _, e := range all {
+			if e.Key == k {
+				found = true
+			}
+		}
+
+		if !found {
+			c.Error("did not find expected key: ", k)
+		}
+	}
 }
 
 func strsToKeys(strs []string) []ds.Key {

Godeps/_workspace/src/github.com/jbenet/go-datastore/key.go

@@ -5,6 +5,8 @@ import (
 	"strings"
 
 	"github.com/jbenet/go-ipfs/Godeps/_workspace/src/code.google.com/p/go-uuid/uuid"
+
+	dsq "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore/query"
 )
 
 /*
@@ -239,3 +241,12 @@ type KeySlice []Key
 func (p KeySlice) Len() int           { return len(p) }
 func (p KeySlice) Less(i, j int) bool { return p[i].Less(p[j]) }
 func (p KeySlice) Swap(i, j int)      { p[i], p[j] = p[j], p[i] }
+
+// EntryKeys
+func EntryKeys(e []dsq.Entry) []Key {
+	ks := make([]Key, len(e))
+	for i, e := range e {
+		ks[i] = NewKey(e.Key)
+	}
+	return ks
+}

Godeps/_workspace/src/github.com/jbenet/go-datastore/keytransform/keytransform.go

@@ -1,6 +1,9 @@
 package keytransform
 
-import ds "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore"
+import (
+	ds "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore"
+	dsq "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore/query"
+)
 
 type Pair struct {
 	Convert KeyMapping
@@ -48,16 +51,25 @@ func (d *ktds) Delete(key ds.Key) (err error) {
 	return d.child.Delete(d.ConvertKey(key))
 }
 
-// KeyList returns a list of all keys in the datastore, transforming keys out.
-func (d *ktds) KeyList() ([]ds.Key, error) {
+// Query implements Query, inverting keys on the way back out.
+func (d *ktds) Query(q dsq.Query) (*dsq.Results, error) {
 
-	keys, err := d.child.KeyList()
+	q2 := q
+	q2.Prefix = d.ConvertKey(ds.NewKey(q2.Prefix)).String()
+	r, err := d.child.Query(q2)
 	if err != nil {
 		return nil, err
 	}
 
-	for i, k := range keys {
-		keys[i] = d.InvertKey(k)
-	}
-	return keys, nil
+	ch := make(chan dsq.Entry)
+	go func() {
+		for e := range r.Entries() {
+			e.Key = d.InvertKey(ds.NewKey(e.Key)).String()
+			ch <- e
+		}
+		close(ch)
+	}()
+
+	r2 := dsq.ResultsWithEntriesChan(q, ch)
+	return r2, nil
 }

Godeps/_workspace/src/github.com/jbenet/go-datastore/keytransform/keytransform_test.go

@@ -5,9 +5,11 @@ import (
 	"sort"
 	"testing"
 
+	. "launchpad.net/gocheck"
+
 	ds "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore"
 	kt "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore/keytransform"
-	. "launchpad.net/gocheck"
+	dsq "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore/query"
 )
 
 // Hook up gocheck into the "go test" runner.
@@ -60,10 +62,13 @@ func (ks *DSSuite) TestBasic(c *C) {
 		c.Check(bytes.Equal(v2.([]byte), []byte(k.String())), Equals, true)
 	}
 
-	listA, errA := mpds.KeyList()
-	listB, errB := ktds.KeyList()
+	listAr, errA := mpds.Query(dsq.Query{})
+	listBr, errB := ktds.Query(dsq.Query{})
 	c.Check(errA, Equals, nil)
 	c.Check(errB, Equals, nil)
+
+	listA := ds.EntryKeys(listAr.AllEntries())
+	listB := ds.EntryKeys(listBr.AllEntries())
 	c.Check(len(listA), Equals, len(listB))
 
 	// sort them cause yeah.
@@ -75,6 +80,9 @@ func (ks *DSSuite) TestBasic(c *C) {
 		c.Check(pair.Invert(kA), Equals, kB)
 		c.Check(kA, Equals, pair.Convert(kB))
 	}
+
+	c.Log("listA: ", listA)
+	c.Log("listB: ", listB)
 }
 
 func strsToKeys(strs []string) []ds.Key {

Godeps/_workspace/src/github.com/jbenet/go-datastore/leveldb/datastore.go

@@ -3,9 +3,12 @@ package leveldb
 import (
 	"io"
 
-	ds "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore"
 	"github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb"
 	"github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/opt"
+	"github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/util"
+
+	ds "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore"
+	dsq "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore/query"
 )
 
 type Datastore interface {
@@ -69,13 +72,54 @@ func (d *datastore) Delete(key ds.Key) (err error) {
 	return err
 }
 
-func (d *datastore) KeyList() ([]ds.Key, error) {
-	i := d.DB.NewIterator(nil, nil)
-	var keys []ds.Key
-	for i.Next() {
-		keys = append(keys, ds.NewKey(string(i.Key())))
+func (d *datastore) Query(q dsq.Query) (*dsq.Results, error) {
+	var rnge *util.Range
+	if q.Prefix != "" {
+		rnge = util.BytesPrefix([]byte(q.Prefix))
 	}
-	return keys, nil
+	i := d.DB.NewIterator(rnge, nil)
+
+	// offset
+	if q.Offset > 0 {
+		for j := 0; j < q.Offset; j++ {
+			i.Next()
+		}
+	}
+
+	var es []dsq.Entry
+	for i.Next() {
+
+		// limit
+		if q.Limit > 0 && len(es) >= q.Limit {
+			break
+		}
+
+		k := ds.NewKey(string(i.Key())).String()
+		e := dsq.Entry{Key: k}
+
+		if !q.KeysOnly {
+			buf := make([]byte, len(i.Value()))
+			copy(buf, i.Value())
+			e.Value = buf
+		}
+
+		es = append(es, e)
+	}
+	i.Release()
+	if err := i.Error(); err != nil {
+		return nil, err
+	}
+
+	// Now, apply remaining pieces.
+	q2 := q
+	q2.Offset = 0 // already applied
+	q2.Limit = 0  // already applied
+	// TODO: make this async with:
+	// qr := dsq.ResultsWithEntriesChan(q, ch)
+	qr := dsq.ResultsWithEntries(q, es)
+	qr = q2.ApplyTo(qr)
+	qr.Query = q // set it back
+	return qr, nil
 }
 
 // LevelDB needs to be closed.

Godeps/_workspace/src/github.com/jbenet/go-datastore/leveldb/ds_test.go

@@ -0,0 +1,99 @@
+package leveldb
+
+import (
+	"io/ioutil"
+	"os"
+	"testing"
+
+	ds "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore"
+	dsq "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore/query"
+)
+
+var testcases = map[string]string{
+	"/a":     "a",
+	"/a/b":   "ab",
+	"/a/b/c": "abc",
+	"/a/b/d": "a/b/d",
+	"/a/c":   "ac",
+	"/a/d":   "ad",
+	"/e":     "e",
+	"/f":     "f",
+}
+
+func TestQuery(t *testing.T) {
+	path, err := ioutil.TempDir("/tmp", "testing_leveldb_")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer func() {
+		os.RemoveAll(path)
+	}()
+
+	d, err := NewDatastore(path, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer d.Close()
+
+	for k, v := range testcases {
+		dsk := ds.NewKey(k)
+		if err := d.Put(dsk, []byte(v)); err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	for k, v := range testcases {
+		dsk := ds.NewKey(k)
+		v2, err := d.Get(dsk)
+		if err != nil {
+			t.Fatal(err)
+		}
+		v2b := v2.([]byte)
+		if string(v2b) != v {
+			t.Errorf("%s values differ: %s != %s", k, v, v2)
+		}
+	}
+
+	rs, err := d.Query(dsq.Query{Prefix: "/a/"})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	expectMatches(t, []string{
+		"/a/b",
+		"/a/b/c",
+		"/a/b/d",
+		"/a/c",
+		"/a/d",
+	}, rs.AllEntries())
+
+	// test offset and limit
+
+	rs, err = d.Query(dsq.Query{Prefix: "/a/", Offset: 2, Limit: 2})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	expectMatches(t, []string{
+		"/a/b/d",
+		"/a/c",
+	}, rs.AllEntries())
+
+}
+
+func expectMatches(t *testing.T, expect []string, actual []dsq.Entry) {
+	if len(actual) != len(expect) {
+		t.Error("not enough", expect, actual)
+	}
+	for _, k := range expect {
+		found := false
+		for _, e := range actual {
+			if e.Key == k {
+				found = true
+			}
+		}
+		if !found {
+			t.Error(k, "not found")
+		}
+	}
+}

Godeps/_workspace/src/github.com/jbenet/go-datastore/lru/datastore.go

@@ -4,7 +4,9 @@ import (
 	"errors"
 
 	lru "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/hashicorp/golang-lru"
+
 	ds "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore"
+	dsq "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore/query"
 )
 
 // Datastore uses golang-lru for internal storage.
@@ -49,6 +51,6 @@ func (d *Datastore) Delete(key ds.Key) (err error) {
 }
 
 // KeyList returns a list of keys in the datastore
-func (d *Datastore) KeyList() ([]ds.Key, error) {
+func (d *Datastore) Query(q dsq.Query) (*dsq.Results, error) {
 	return nil, errors.New("KeyList not implemented.")
 }

Godeps/_workspace/src/github.com/jbenet/go-datastore/namespace/namespace_test.go

@@ -5,9 +5,11 @@ import (
 	"sort"
 	"testing"
 
+	. "launchpad.net/gocheck"
+
 	ds "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore"
 	ns "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore/namespace"
-	. "launchpad.net/gocheck"
+	dsq "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore/query"
 )
 
 // Hook up gocheck into the "go test" runner.
@@ -46,10 +48,13 @@ func (ks *DSSuite) TestBasic(c *C) {
 		c.Check(bytes.Equal(v2.([]byte), []byte(k.String())), Equals, true)
 	}
 
-	listA, errA := mpds.KeyList()
-	listB, errB := nsds.KeyList()
+	listAr, errA := mpds.Query(dsq.Query{})
+	listBr, errB := nsds.Query(dsq.Query{})
 	c.Check(errA, Equals, nil)
 	c.Check(errB, Equals, nil)
+
+	listA := ds.EntryKeys(listAr.AllEntries())
+	listB := ds.EntryKeys(listBr.AllEntries())
 	c.Check(len(listA), Equals, len(listB))
 
 	// sort them cause yeah.

Godeps/_workspace/src/github.com/jbenet/go-datastore/panic/panic.go

@@ -5,6 +5,7 @@ import (
 	"os"
 
 	ds "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore"
+	dsq "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore/query"
 )
 
 type datastore struct {
@@ -57,11 +58,11 @@ func (d *datastore) Delete(key ds.Key) error {
 	return nil
 }
 
-func (d *datastore) KeyList() ([]ds.Key, error) {
-	kl, err := d.child.KeyList()
+func (d *datastore) Query(q dsq.Query) (*dsq.Results, error) {
+	r, err := d.child.Query(q)
 	if err != nil {
 		fmt.Fprintf(os.Stdout, "panic datastore: %s", err)
-		panic("panic datastore: KeyList failed")
+		panic("panic datastore: Query failed")
 	}
-	return kl, nil
+	return r, nil
 }

Godeps/_workspace/src/github.com/jbenet/go-datastore/query/filter.go

@@ -0,0 +1,86 @@
+package query
+
+import (
+	"fmt"
+	"reflect"
+	"strings"
+)
+
+// Filter is an object that tests ResultEntries
+type Filter interface {
+	// Filter returns whether an entry passes the filter
+	Filter(e Entry) bool
+}
+
+// Op is a comparison operator
+type Op string
+
+var (
+	Equal              = Op("==")
+	NotEqual           = Op("!=")
+	GreaterThan        = Op(">")
+	GreaterThanOrEqual = Op(">=")
+	LessThan           = Op("<")
+	LessThanOrEqual    = Op("<=")
+)
+
+// FilterValueCompare is used to signal to datastores they
+// should apply internal comparisons. unfortunately, there
+// is no way to apply comparisons* to interface{} types in
+// Go, so if the datastore doesnt have a special way to
+// handle these comparisons, you must provided the
+// TypedFilter to actually do filtering.
+//
+// [*] other than == and !=, which use reflect.DeepEqual.
+type FilterValueCompare struct {
+	Op          Op
+	Value       interface{}
+	TypedFilter Filter
+}
+
+func (f FilterValueCompare) Filter(e Entry) bool {
+	if f.TypedFilter != nil {
+		return f.TypedFilter.Filter(e)
+	}
+
+	switch f.Op {
+	case Equal:
+		return reflect.DeepEqual(f.Value, e.Value)
+	case NotEqual:
+		return !reflect.DeepEqual(f.Value, e.Value)
+	default:
+		panic(fmt.Errorf("cannot apply op '%s' to interface{}.", f.Op))
+	}
+}
+
+type FilterKeyCompare struct {
+	Op  Op
+	Key string
+}
+
+func (f FilterKeyCompare) Filter(e Entry) bool {
+	switch f.Op {
+	case Equal:
+		return e.Key == f.Key
+	case NotEqual:
+		return e.Key != f.Key
+	case GreaterThan:
+		return e.Key > f.Key
+	case GreaterThanOrEqual:
+		return e.Key >= f.Key
+	case LessThan:
+		return e.Key < f.Key
+	case LessThanOrEqual:
+		return e.Key <= f.Key
+	default:
+		panic(fmt.Errorf("unknown op '%s'", f.Op))
+	}
+}
+
+type FilterKeyPrefix struct {
+	Prefix string
+}
+
+func (f FilterKeyPrefix) Filter(e Entry) bool {
+	return strings.HasPrefix(e.Key, f.Prefix)
+}

Godeps/_workspace/src/github.com/jbenet/go-datastore/query/filter_test.go

@@ -0,0 +1,75 @@
+package query
+
+import (
+	"strings"
+	"testing"
+)
+
+var sampleKeys = []string{
+	"/ab/c",
+	"/ab/cd",
+	"/a",
+	"/abce",
+	"/abcf",
+	"/ab",
+}
+
+type filterTestCase struct {
+	filter Filter
+	keys   []string
+	expect []string
+}
+
+func testKeyFilter(t *testing.T, f Filter, keys []string, expect []string) {
+	e := make([]Entry, len(keys))
+	for i, k := range keys {
+		e[i] = Entry{Key: k}
+	}
+
+	res := ResultsWithEntries(Query{}, e)
+	res = NaiveFilter(res, f)
+	actualE := res.AllEntries()
+	actual := make([]string, len(actualE))
+	for i, e := range actualE {
+		actual[i] = e.Key
+	}
+
+	if len(actual) != len(expect) {
+		t.Error("expect != actual.", expect, actual)
+	}
+
+	if strings.Join(actual, "") != strings.Join(expect, "") {
+		t.Error("expect != actual.", expect, actual)
+	}
+}
+
+func TestFilterKeyCompare(t *testing.T) {
+
+	testKeyFilter(t, FilterKeyCompare{Equal, "/ab"}, sampleKeys, []string{"/ab"})
+	testKeyFilter(t, FilterKeyCompare{GreaterThan, "/ab"}, sampleKeys, []string{
+		"/ab/c",
+		"/ab/cd",
+		"/abce",
+		"/abcf",
+	})
+	testKeyFilter(t, FilterKeyCompare{LessThanOrEqual, "/ab"}, sampleKeys, []string{
+		"/a",
+		"/ab",
+	})
+}
+
+func TestFilterKeyPrefix(t *testing.T) {
+
+	testKeyFilter(t, FilterKeyPrefix{"/a"}, sampleKeys, []string{
+		"/ab/c",
+		"/ab/cd",
+		"/a",
+		"/abce",
+		"/abcf",
+		"/ab",
+	})
+	testKeyFilter(t, FilterKeyPrefix{"/ab/"}, sampleKeys, []string{
+		"/ab/c",
+		"/ab/cd",
+	})
+}

Godeps/_workspace/src/github.com/jbenet/go-datastore/query/order.go

@@ -0,0 +1,66 @@
+package query
+
+import (
+	"sort"
+)
+
+// Order is an object used to order objects
+type Order interface {
+
+	// Sort sorts the Entry slice according to
+	// the Order criteria.
+	Sort([]Entry)
+}
+
+// OrderByValue is used to signal to datastores they
+// should apply internal orderings. unfortunately, there
+// is no way to apply order comparisons to interface{} types
+// in Go, so if the datastore doesnt have a special way to
+// handle these comparisons, you must provide an Order
+// implementation that casts to the correct type.
+type OrderByValue struct {
+	TypedOrder Order
+}
+
+func (o OrderByValue) Sort(res []Entry) {
+	if o.TypedOrder == nil {
+		panic("cannot order interface{} by value. see query docs.")
+	}
+	o.TypedOrder.Sort(res)
+}
+
+// OrderByValueDescending is used to signal to datastores they
+// should apply internal orderings. unfortunately, there
+// is no way to apply order comparisons to interface{} types
+// in Go, so if the datastore doesnt have a special way to
+// handle these comparisons, you are SOL.
+type OrderByValueDescending struct {
+	TypedOrder Order
+}
+
+func (o OrderByValueDescending) Sort(res []Entry) {
+	if o.TypedOrder == nil {
+		panic("cannot order interface{} by value. see query docs.")
+	}
+	o.TypedOrder.Sort(res)
+}
+
+// OrderByKey
+type OrderByKey struct{}
+
+func (o OrderByKey) Sort(res []Entry) {
+	sort.Stable(reByKey(res))
+}
+
+// OrderByKeyDescending
+type OrderByKeyDescending struct{}
+
+func (o OrderByKeyDescending) Sort(res []Entry) {
+	sort.Stable(sort.Reverse(reByKey(res)))
+}
+
+type reByKey []Entry
+
+func (s reByKey) Len() int           { return len(s) }
+func (s reByKey) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }
+func (s reByKey) Less(i, j int) bool { return s[i].Key < s[j].Key }

Godeps/_workspace/src/github.com/jbenet/go-datastore/query/order_test.go

@@ -0,0 +1,55 @@
+package query
+
+import (
+	"strings"
+	"testing"
+)
+
+type orderTestCase struct {
+	order  Order
+	keys   []string
+	expect []string
+}
+
+func testKeyOrder(t *testing.T, f Order, keys []string, expect []string) {
+	e := make([]Entry, len(keys))
+	for i, k := range keys {
+		e[i] = Entry{Key: k}
+	}
+
+	res := ResultsWithEntries(Query{}, e)
+	res = NaiveOrder(res, f)
+	actualE := res.AllEntries()
+	actual := make([]string, len(actualE))
+	for i, e := range actualE {
+		actual[i] = e.Key
+	}
+
+	if len(actual) != len(expect) {
+		t.Error("expect != actual.", expect, actual)
+	}
+
+	if strings.Join(actual, "") != strings.Join(expect, "") {
+		t.Error("expect != actual.", expect, actual)
+	}
+}
+
+func TestOrderByKey(t *testing.T) {
+
+	testKeyOrder(t, OrderByKey{}, sampleKeys, []string{
+		"/a",
+		"/ab",
+		"/ab/c",
+		"/ab/cd",
+		"/abce",
+		"/abcf",
+	})
+	testKeyOrder(t, OrderByKeyDescending{}, sampleKeys, []string{
+		"/abcf",
+		"/abce",
+		"/ab/cd",
+		"/ab/c",
+		"/ab",
+		"/a",
+	})
+}

Godeps/_workspace/src/github.com/jbenet/go-datastore/query/query.go

@@ -0,0 +1,145 @@
+package query
+
+/*
+Query represents storage for any key-value pair.
+
+tl;dr:
+
+  queries are supported across datastores.
+  Cheap on top of relational dbs, and expensive otherwise.
+  Pick the right tool for the job!
+
+In addition to the key-value store get and set semantics, datastore
+provides an interface to retrieve multiple records at a time through
+the use of queries. The datastore Query model gleans a common set of
+operations performed when querying. To avoid pasting here years of
+database research, let’s summarize the operations datastore supports.
+
+Query Operations:
+
+  * namespace - scope the query, usually by object type
+  * filters - select a subset of values by applying constraints
+  * orders - sort the results by applying sort conditions
+  * limit - impose a numeric limit on the number of results
+  * offset - skip a number of results (for efficient pagination)
+
+datastore combines these operations into a simple Query class that allows
+applications to define their constraints in a simple, generic, way without
+introducing datastore specific calls, languages, etc.
+
+Of course, different datastores provide relational query support across a
+wide spectrum, from full support in traditional databases to none at all in
+most key-value stores. Datastore aims to provide a common, simple interface
+for the sake of application evolution over time and keeping large code bases
+free of tool-specific code. It would be ridiculous to claim to support high-
+performance queries on architectures that obviously do not. Instead, datastore
+provides the interface, ideally translating queries to their native form
+(e.g. into SQL for MySQL).
+
+However, on the wrong datastore, queries can potentially incur the high cost
+of performing the aforemantioned query operations on the data set directly in
+Go. It is the client’s responsibility to select the right tool for the job:
+pick a data storage solution that fits the application’s needs now, and wrap
+it with a datastore implementation. As the needs change, swap out datastore
+implementations to support your new use cases. Some applications, particularly
+in early development stages, can afford to incurr the cost of queries on non-
+relational databases (e.g. using a FSDatastore and not worry about a database
+at all). When it comes time to switch the tool for performance, updating the
+application code can be as simple as swapping the datastore in one place, not
+all over the application code base. This gain in engineering time, both at
+initial development and during later iterations, can significantly offset the
+cost of the layer of abstraction.
+
+*/
+type Query struct {
+	Prefix   string   // namespaces the query to results whose keys have Prefix
+	Filters  []Filter // filter results. apply sequentially
+	Orders   []Order  // order results. apply sequentially
+	Limit    int      // maximum number of results
+	Offset   int      // skip given number of results
+	KeysOnly bool     // return only keys.
+}
+
+// NotFetched is a special type that signals whether or not the value
+// of an Entry has been fetched or not. This is needed because
+// datastore implementations get to decide whether Query returns values
+// or only keys. nil is not a good signal, as real values may be nil.
+var NotFetched = struct{}{}
+
+// Entry is a query result entry.
+type Entry struct {
+	Key   string // cant be ds.Key because circular imports ...!!!
+	Value interface{}
+}
+
+// Results is a set of Query results
+type Results struct {
+	Query Query // the query these Results correspond to
+
+	done chan struct{}
+	res  chan Entry
+	all  []Entry
+}
+
+// ResultsWithEntriesChan returns a Results object from a
+// channel of ResultEntries. It's merely an encapsulation
+// that provides for AllEntries() functionality.
+func ResultsWithEntriesChan(q Query, res <-chan Entry) *Results {
+	r := &Results{
+		Query: q,
+		done:  make(chan struct{}),
+		res:   make(chan Entry),
+		all:   []Entry{},
+	}
+
+	// go consume all the results and add them to the results.
+	go func() {
+		for e := range res {
+			r.all = append(r.all, e)
+			r.res <- e
+		}
+		close(r.res)
+		close(r.done)
+	}()
+	return r
+}
+
+// ResultsWithEntries returns a Results object from a
+// channel of ResultEntries. It's merely an encapsulation
+// that provides for AllEntries() functionality.
+func ResultsWithEntries(q Query, res []Entry) *Results {
+	r := &Results{
+		Query: q,
+		done:  make(chan struct{}),
+		res:   make(chan Entry),
+		all:   res,
+	}
+
+	// go add all the results
+	go func() {
+		for _, e := range res {
+			r.res <- e
+		}
+		close(r.res)
+		close(r.done)
+	}()
+	return r
+}
+
+// Entries() returns results through a channel.
+// Results may arrive at any time.
+// The channel may or may not be buffered.
+// The channel may or may not rate limit the query processing.
+func (r *Results) Entries() <-chan Entry {
+	return r.res
+}
+
+// AllEntries returns all the entries in Results.
+// It blocks until all the results have come in.
+func (r *Results) AllEntries() []Entry {
+	for e := range r.res {
+		_ = e
+	}
+	<-r.done
+	return r.all
+}

Godeps/_workspace/src/github.com/jbenet/go-datastore/query/query_impl.go

@@ -0,0 +1,85 @@
+package query
+
+// NaiveFilter applies a filter to the results
+func NaiveFilter(qr *Results, filter Filter) *Results {
+	ch := make(chan Entry)
+	go func() {
+		defer close(ch)
+
+		for e := range qr.Entries() {
+			if filter.Filter(e) {
+				ch <- e
+			}
+		}
+	}()
+	return ResultsWithEntriesChan(qr.Query, ch)
+}
+
+// NaiveLimit truncates the results to a given int limit
+func NaiveLimit(qr *Results, limit int) *Results {
+	ch := make(chan Entry)
+	go func() {
+		defer close(ch)
+
+		for l := 0; l < limit; l++ {
+			e, more := <-qr.Entries()
+			if !more {
+				return
+			}
+			ch <- e
+		}
+	}()
+	return ResultsWithEntriesChan(qr.Query, ch)
+}
+
+// NaiveOffset skips a given number of results
+func NaiveOffset(qr *Results, offset int) *Results {
+	ch := make(chan Entry)
+	go func() {
+		defer close(ch)
+
+		for l := 0; l < offset; l++ {
+			<-qr.Entries() // discard
+		}
+
+		for e := range qr.Entries() {
+			ch <- e
+		}
+	}()
+	return ResultsWithEntriesChan(qr.Query, ch)
+}
+
+// NaiveOrder reorders results according to given Order.
+// WARNING: this is the only non-stream friendly operation!
+func NaiveOrder(qr *Results, o Order) *Results {
+	e := qr.AllEntries()
+	o.Sort(e)
+	return ResultsWithEntries(qr.Query, e)
+}
+
+func (q Query) ApplyTo(qr *Results) *Results {
+	if q.Prefix != "" {
+		qr = NaiveFilter(qr, FilterKeyPrefix{q.Prefix})
+	}
+	for _, f := range q.Filters {
+		qr = NaiveFilter(qr, f)
+	}
+	for _, o := range q.Orders {
+		qr = NaiveOrder(qr, o)
+	}
+	if q.Offset != 0 {
+		qr = NaiveOffset(qr, q.Offset)
+	}
+	if q.Limit != 0 {
+		qr = NaiveLimit(qr, q.Offset)
+	}
+	return qr
+}
+
+func ResultEntriesFrom(keys []string, vals []interface{}) []Entry {
+	re := make([]Entry, len(keys))
+	for i, k := range keys {
+		re[i] = Entry{Key: k, Value: vals[i]}
+	}
+	return re
+}

Godeps/_workspace/src/github.com/jbenet/go-datastore/sync/sync.go

@@ -4,6 +4,7 @@ import (
 	"sync"
 
 	ds "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore"
+	dsq "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore/query"
 )
 
 // MutexDatastore contains a child datastire and a mutex.
@@ -57,8 +58,8 @@ func (d *MutexDatastore) Delete(key ds.Key) (err error) {
 }
 
 // KeyList implements Datastore.KeyList
-func (d *MutexDatastore) KeyList() ([]ds.Key, error) {
+func (d *MutexDatastore) Query(q dsq.Query) (*dsq.Results, error) {
 	d.RLock()
 	defer d.RUnlock()
-	return d.child.KeyList()
+	return d.child.Query(q)
 }

blocks/blockstore/write_cache_test.go

@@ -4,6 +4,7 @@ import (
 	"testing"
 
 	ds "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore"
+	dsq "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore/query"
 	syncds "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore/sync"
 	"github.com/jbenet/go-ipfs/blocks"
 )
@@ -83,7 +84,7 @@ func (c *callbackDatastore) Delete(key ds.Key) (err error) {
 	return c.ds.Delete(key)
 }
 
-func (c *callbackDatastore) KeyList() ([]ds.Key, error) {
+func (c *callbackDatastore) Query(q dsq.Query) (*dsq.Results, error) {
 	c.f()
-	return c.ds.KeyList()
+	return c.ds.Query(q)
 }

util/datastore2/delayed.go

@@ -1,42 +1,44 @@
 package datastore2
 
 import (
-	datastore "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore"
+	ds "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore"
+	dsq "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore/query"
+
 	delay "github.com/jbenet/go-ipfs/util/delay"
 )
 
-func WithDelay(ds datastore.Datastore, delay delay.D) datastore.Datastore {
+func WithDelay(ds ds.Datastore, delay delay.D) ds.Datastore {
 	return &delayed{ds: ds, delay: delay}
 }
 
 type delayed struct {
-	ds    datastore.Datastore
+	ds    ds.Datastore
 	delay delay.D
 }
 
-func (dds *delayed) Put(key datastore.Key, value interface{}) (err error) {
+func (dds *delayed) Put(key ds.Key, value interface{}) (err error) {
 	dds.delay.Wait()
 	return dds.ds.Put(key, value)
 }
 
-func (dds *delayed) Get(key datastore.Key) (value interface{}, err error) {
+func (dds *delayed) Get(key ds.Key) (value interface{}, err error) {
 	dds.delay.Wait()
 	return dds.ds.Get(key)
 }
 
-func (dds *delayed) Has(key datastore.Key) (exists bool, err error) {
+func (dds *delayed) Has(key ds.Key) (exists bool, err error) {
 	dds.delay.Wait()
 	return dds.ds.Has(key)
 }
 
-func (dds *delayed) Delete(key datastore.Key) (err error) {
+func (dds *delayed) Delete(key ds.Key) (err error) {
 	dds.delay.Wait()
 	return dds.ds.Delete(key)
 }
 
-func (dds *delayed) KeyList() ([]datastore.Key, error) {
+func (dds *delayed) Query(q dsq.Query) (*dsq.Results, error) {
 	dds.delay.Wait()
-	return dds.ds.KeyList()
+	return dds.ds.Query(q)
 }
 
-var _ datastore.Datastore = &delayed{}
+var _ ds.Datastore = &delayed{}