Fix issue in fetching the max key when keys are substrings of each other

Authored by: Marty Schoch <[email protected]> See conversation on: blevesearch/bleve#1096 Change-Id: I9a63f6bd5e0605ac3a48ba42076bbf6959f1448e Reviewed-on: http://review.couchbase.org/103303 Well-Formed: Build Bot <[email protected]> Reviewed-by: Steve Yen <[email protected]> Reviewed-by: Sreekanth Sivasankaran <[email protected]> Tested-by: Abhinav Dangeti <[email protected]>
couchbase · Jan 7, 2019 · 28880ab · 28880ab
1 parent dd17fb8
commit 28880ab
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Showing 2 changed files with 79 additions and 17 deletions.
diff --git a/fst.go b/fst.go
@@ -243,7 +243,7 @@ func (f *FST) Reader() (*Reader, error) {
 	return &Reader{f: f}, nil
 }
 
-func (f *FST) getMinMaxKey(comparator func(byte, byte) bool) ([]byte, error) {
+func (f *FST) GetMinKey() ([]byte, error) {
 	var rv []byte
 
 	curr := f.decoder.getRoot()
@@ -253,34 +253,40 @@ func (f *FST) getMinMaxKey(comparator func(byte, byte) bool) ([]byte, error) {
 	}
 
 	for !state.Final() {
-		lastTransition := state.TransitionAt(0)
-		numTransitions := state.NumTransitions()
-		for i := 1; i < numTransitions; i++ {
-			transition := state.TransitionAt(i)
-			if comparator(transition, lastTransition) {
-				lastTransition = transition
-			}
-		}
-
-		_, curr, _ = state.TransitionFor(lastTransition)
+		nextTrans := state.TransitionAt(0)
+		_, curr, _ = state.TransitionFor(nextTrans)
 		state, err = f.decoder.stateAt(curr, state)
 		if err != nil {
 			return nil, err
 		}
 
-		rv = append(rv, lastTransition)
+		rv = append(rv, nextTrans)
 	}
 
 	return rv, nil
 }
 
-func (f *FST) GetMinKey() ([]byte, error) {
-	return f.getMinMaxKey(func (x byte, y byte) bool {return x < y})
-}
+func (f *FST) GetMaxKey() ([]byte, error) {
+	var rv []byte
 
+	curr := f.decoder.getRoot()
+	state, err := f.decoder.stateAt(curr, nil)
+	if err != nil {
+		return nil, err
+	}
 
-func (f *FST) GetMaxKey() ([]byte, error) {
-	return f.getMinMaxKey(func (x byte, y byte) bool {return x > y})
+	for state.NumTransitions() > 0 {
+		nextTrans := state.TransitionAt(state.NumTransitions() - 1)
+		_, curr, _ = state.TransitionFor(nextTrans)
+		state, err = f.decoder.stateAt(curr, state)
+		if err != nil {
+			return nil, err
+		}
+
+		rv = append(rv, nextTrans)
+	}
+
+	return rv, nil
 }
 
 // A Reader is meant for a single threaded use

diff --git a/vellum_test.go b/vellum_test.go
@@ -638,3 +638,59 @@ func benchmarkBigKey(b *testing.B, n int) {
 		}
 	}
 }
+
+func TestMaxWithSubstring(t *testing.T) {
+	var buf bytes.Buffer
+	builder, err := New(&buf, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = builder.Insert([]byte("1"), 1)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = builder.Insert([]byte("11"), 1)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = builder.Insert([]byte("9"), 9)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = builder.Insert([]byte("99"), 99)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = builder.Close()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	fst, err := Load(buf.Bytes())
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	mink, err := fst.GetMinKey()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if string(mink) != "1" {
+		t.Fatalf("expected max key 1, got %s", string(mink))
+	}
+
+	maxk, err := fst.GetMaxKey()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if string(maxk) != "99" {
+		t.Fatalf("expected max key 99, got %s", string(maxk))
+	}
+}