query: send back errors when channels somehow

this is not a good inteface. should fix it

datastore.go

@@ -79,6 +79,15 @@ func (d *datastore) Query(q dsq.Query) (*dsq.Results, error) {
 	}
 	i := d.DB.NewIterator(rnge, nil)
 
+	// buffer this channel so that we dont totally block leveldb if client
+	// is not reading from chan.
+	ch := make(chan dsq.Entry, 1000)
+	qr := dsq.ResultsWithEntriesChan(q, ch)
+	// qr := dsq.ResultsWithEntries(q, es)
+
+	go func() {
+		defer close(ch)
+
 		// offset
 		if q.Offset > 0 {
 			for j := 0; j < q.Offset; j++ {
@@ -86,11 +95,11 @@ func (d *datastore) Query(q dsq.Query) (*dsq.Results, error) {
 			}
 		}
 
-	var es []dsq.Entry
+		sent := 0
 		for i.Next() {
 
 			// limit
-		if q.Limit > 0 && len(es) >= q.Limit {
+			if q.Limit > 0 && sent >= q.Limit {
 				break
 			}
 
@@ -103,20 +112,20 @@ func (d *datastore) Query(q dsq.Query) (*dsq.Results, error) {
 				e.Value = buf
 			}
 
-		es = append(es, e)
+			ch <- e
+			sent++
 		}
 		i.Release()
 		if err := i.Error(); err != nil {
-		return nil, err
+			qr.Err() <- 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