Results.Close should return error

keytransform/keytransform.go

@@ -94,8 +94,8 @@ func (d *Datastore) Query(ctx context.Context, q dsq.Query) (dsq.Results, error)
 			}
 			return r, true
 		},
-		Close: func() {
-			cqr.Close()
+		Close: func() error {
+			return cqr.Close()
 		},
 	})
 	return dsq.NaiveQueryApply(nq, qr), nil

mount/mount.go

@@ -140,11 +140,12 @@ func (h *querySet) Pop() interface{} {
 	return last
 }
 
-func (h *querySet) close() {
+func (h *querySet) close() error {
 	for _, qr := range h.heads {
 		qr.results.Close()
 	}
 	h.heads = nil
+	return nil
 }
 
 func (h *querySet) addResults(mount ds.Key, results query.Results) {

query/query.go

@@ -153,7 +153,7 @@ type Results interface {
 	Next() <-chan Result      // returns a channel to wait for the next result
 	NextSync() (Result, bool) // blocks and waits to return the next result, second parameter returns false when results are exhausted
 	Rest() ([]Entry, error)   // waits till processing finishes, returns all entries at once.
-	Close()                   // client may call Close to signal early exit
+	Close() error             // client may call Close to signal early exit
 	Done() <-chan struct{}    // signals that Results is closed
 }
 
@@ -187,9 +187,10 @@ func (r *results) Rest() ([]Entry, error) {
 	return es, nil
 }
 
-func (r *results) Close() {
+func (r *results) Close() error {
 	r.cancel()
 	<-r.closed
+	return nil
 }
 
 func (r *results) Query() Query {
@@ -273,17 +274,17 @@ func ResultsFromIterator(q Query, iter Iterator) Results {
 	}
 }
 
-func noopClose() {}
+func noopClose() error { return nil }
 
 type Iterator struct {
 	Next  func() (Result, bool)
-	Close func() // note: might be called more than once
+	Close func() error // note: might be called more than once
 }
 
 type resultsIter struct {
 	query   Query
 	next    func() (Result, bool)
-	close   func()
+	close   func() error
 	results *results
 }
 
@@ -318,14 +319,15 @@ func (r *resultsIter) Rest() ([]Entry, error) {
 	return es, nil
 }
 
-func (r *resultsIter) Close() {
+func (r *resultsIter) Close() error {
 	if r.results != nil {
 		// Close results collector. It will call r.close().
 		r.results.Close()
 	} else {
 		// Call r.close() since there is no collector to call it when closed.
 		r.close()
 	}
+	return nil
 }
 
 func (r *resultsIter) Query() Query {

query/query_impl.go

@@ -18,8 +18,8 @@ func NaiveFilter(qr Results, filter Filter) Results {
 				}
 			}
 		},
-		Close: func() {
-			qr.Close()
+		Close: func() error {
+			return qr.Close()
 		},
 	})
 }
@@ -43,12 +43,12 @@ func NaiveLimit(qr Results, limit int) Results {
 			limit--
 			return qr.NextSync()
 		},
-		Close: func() {
+		Close: func() error {
 			if closed {
-				return
+				return nil
 			}
 			closed = true
-			qr.Close()
+			return qr.Close()
 		},
 	})
 }
@@ -65,8 +65,8 @@ func NaiveOffset(qr Results, offset int) Results {
 			}
 			return qr.NextSync()
 		},
-		Close: func() {
-			qr.Close()
+		Close: func() error {
+			return qr.Close()
 		},
 	})
 }

query/query_test.go

@@ -200,7 +200,7 @@ func TestResultsFromIteratorNoClose(t *testing.T) {
 	testResultsFromIterator(t, getKeysViaChan, nil)
 }
 
-func testResultsFromIterator(t *testing.T, getKeys func(rs Results) []string, close func()) {
+func testResultsFromIterator(t *testing.T, getKeys func(rs Results) []string, close func() error) {
 	i := 0
 	results := ResultsFromIterator(Query{}, Iterator{
 		Next: func() (Result, bool) {
@@ -221,8 +221,9 @@ func testResultsFromIterator(t *testing.T, getKeys func(rs Results) []string, cl
 
 func testResultsFromIteratorWClose(t *testing.T, getKeys func(rs Results) []string) {
 	closeCalled := 0
-	testResultsFromIterator(t, getKeys, func() {
+	testResultsFromIterator(t, getKeys, func() error {
 		closeCalled++
+		return nil
 	})
 	if closeCalled != 1 {
 		t.Errorf("close called %d times, expect it to be called just once", closeCalled)