Add a test for compression

Signed-off-by: Chris Marchbanks <[email protected]>

Author: csmarchbanks

wal/wal_test.go

@@ -370,6 +370,65 @@ func TestSegmentMetric(t *testing.T) {
 	testutil.Ok(t, w.Close())
 }
 
+func TestCompression(t *testing.T) {
+	const (
+		segmentSize = pageSize
+		recordSize  = (pageSize / 2) - recordHeaderSize
+		records     = 100
+	)
+
+	uncompressedDir, err := ioutil.TempDir("", "uncompressed")
+	testutil.Ok(t, err)
+	defer func() {
+		testutil.Ok(t, os.RemoveAll(uncompressedDir))
+	}()
+	w, err := NewSize(nil, nil, uncompressedDir, segmentSize, false)
+	testutil.Ok(t, err)
+
+	logZeroRecords(t, w, recordSize, records)
+	testutil.Ok(t, w.Close())
+
+	compressedDir, err := ioutil.TempDir("", "uncompressed")
+	testutil.Ok(t, err)
+	defer func() {
+		testutil.Ok(t, os.RemoveAll(compressedDir))
+	}()
+	w, err = NewSize(nil, nil, compressedDir, segmentSize, true)
+	testutil.Ok(t, err)
+
+	logZeroRecords(t, w, recordSize, records)
+	testutil.Ok(t, w.Close())
+
+	uncompressedSize, err := dirSize(uncompressedDir)
+	testutil.Ok(t, err)
+	compressedSize, err := dirSize(compressedDir)
+	testutil.Ok(t, err)
+
+	testutil.Assert(t, float64(uncompressedSize)*0.75 > float64(compressedSize), "Compressing zeroes should save at least 25%% space")
+}
+
+func logZeroRecords(tb testing.TB, w *WAL, recordSize, records int) {
+	tb.Helper()
+	buf := make([]byte, recordSize)
+	for i := 0; i < records; i++ {
+		testutil.Ok(tb, w.Log(buf))
+	}
+}
+
+func dirSize(path string) (int64, error) {
+	var size int64
+	err := filepath.Walk(path, func(_ string, info os.FileInfo, err error) error {
+		if err != nil {
+			return err
+		}
+		if !info.IsDir() {
+			size += info.Size()
+		}
+		return nil
+	})
+	return size, err
+}
+
 func BenchmarkWAL_LogBatched(b *testing.B) {
 	for _, compress := range []bool{true, false} {
 		b.Run(fmt.Sprintf("compress=%t", compress), func(b *testing.B) {