Merge pull request #129 from ipfs/fix/sync-query

sync: apply entire query while locked

Author: Stebalien

query/query.go

@@ -245,22 +245,17 @@ func ResultsWithProcess(q Query, proc func(goprocess.Process, chan<- Result)) Re
 
 // ResultsWithEntries returns a Results object from a list of entries
 func ResultsWithEntries(q Query, res []Entry) Results {
-	b := NewResultBuilder(q)
-
-	// go consume all the entries and add them to the results.
-	b.Process.Go(func(worker goprocess.Process) {
-		for _, e := range res {
-			select {
-			case b.Output <- Result{Entry: e}:
-			case <-worker.Closing(): // client told us to close early
-				return
+	i := 0
+	return ResultsFromIterator(q, Iterator{
+		Next: func() (Result, bool) {
+			if i >= len(res) {
+				return Result{}, false
 			}
-		}
-		return
+			next := res[i]
+			i++
+			return Result{Entry: next}, true
+		},
 	})
-
-	go b.Process.CloseAfterChildren()
-	return b.Results()
 }
 
 func ResultsReplaceQuery(r Results, q Query) Results {

sync/sync.go

@@ -61,11 +61,28 @@ func (d *MutexDatastore) Delete(key ds.Key) (err error) {
 	return d.child.Delete(key)
 }
 
-// KeyList implements Datastore.KeyList
+// Query implements Datastore.Query
 func (d *MutexDatastore) Query(q dsq.Query) (dsq.Results, error) {
 	d.RLock()
 	defer d.RUnlock()
-	return d.child.Query(q)
+
+	// Apply the entire query while locked. Non-sync datastores may not
+	// allow concurrent queries.
+
+	results, err := d.child.Query(q)
+	if err != nil {
+		return nil, err
+	}
+
+	entries, err1 := results.Rest()
+	err2 := results.Close()
+	switch {
+	case err1 != nil:
+		return nil, err1
+	case err2 != nil:
+		return nil, err2
+	}
+	return dsq.ResultsWithEntries(q, entries), nil
 }
 
 func (d *MutexDatastore) Batch() (ds.Batch, error) {