Function TestDB_MaxSizeExceededCanOpenWithHighMmap

db_test.go:1632–1655

Ensure that opening a database that is beyond the maximum size succeeds, even when InitialMmapSize is above the limit (mmaps should not affect file size) https://github.com/etcd-io/bbolt/issues/928

(t *testing.T)

// even when InitialMmapSize is above the limit (mmaps should not affect file size)
// https://github.com/etcd-io/bbolt/issues/928
func TestDB_MaxSizeExceededCanOpenWithHighMmap(t *testing.T) {
	// Open a data file.
	db := createFilledDB(t, nil, 4*1024*1024, 2000) // adjust allocation jumps to 4 MiB, fill with 2000 1KB entries
	path := db.Path()

	err := db.Close()
	require.NoError(t, err, "Close should succeed")

	// The data file should be 4 MiB now (expanded once from zero).
	minimumSizeForTest := int64(1024 * 1024)
	newSz := fileSize(path)
	require.GreaterOrEqual(t, newSz, minimumSizeForTest, "unexpected new file size: %d. Expected at least %d", newSz, minimumSizeForTest)

	// Now try to re-open the database with an extremely small max size
	t.Logf("Reopening bbolt DB at: %s", path)
	db, err = btesting.OpenDBWithOption(t, path, &bolt.Options{
		MaxSize:         1,
		InitialMmapSize: int(minimumSizeForTest) * 2,
	})
	assert.NoError(t, err, "Should be able to open database bigger than MaxSize when InitialMmapSize set high")

	err = db.Close()
	require.NoError(t, err, "Closing the re-opened database should succeed")
}

// Ensure that on Windows, mmap never expands the file speculatively via
// InitialMmapSize, and that the database remains fully usable after such an