fix CQ snapshot compatibility

Author: DaZuiZui

iotdb-core/confignode/src/main/java/org/apache/iotdb/confignode/persistence/cq/CQInfo.java

@@ -317,13 +317,21 @@ private void serialize(OutputStream stream) throws IOException {
   private void deserialize(InputStream stream) throws IOException {
     int markerOrSize = ReadWriteIOUtils.readInt(stream);
     final boolean structured;
+    final boolean hasOccurrenceIndex;
     final int size;
-    if (markerOrSize == SNAPSHOT_VERSION || markerOrSize == PREVIOUS_SNAPSHOT_VERSION) {
+    if (markerOrSize == SNAPSHOT_VERSION) {
       structured = true;
+      hasOccurrenceIndex = true;
+      size = ReadWriteIOUtils.readInt(stream);
+    } else if (markerOrSize == PREVIOUS_SNAPSHOT_VERSION) {
+      // The first structured snapshot format did not persist nextOccurrenceIndex yet.
+      structured = true;
+      hasOccurrenceIndex = false;
       size = ReadWriteIOUtils.readInt(stream);
     } else if (markerOrSize >= 0) {
       // Snapshots written before structured duration support started with the CQ count.
       structured = false;
+      hasOccurrenceIndex = false;
       size = markerOrSize;
     } else {
       throw new IOException(
@@ -337,7 +345,7 @@ private void deserialize(InputStream stream) throws IOException {
               ManagerMessages.EXCEPTION_NEGATIVE_CQ_SNAPSHOT_ENTRY_COUNT_ARG_38750035, size));
     }
     for (int i = 0; i < size; i++) {
-      CQEntry cqEntry = CQEntry.deserialize(stream, structured);
+      CQEntry cqEntry = CQEntry.deserialize(stream, structured, hasOccurrenceIndex);
       cqMap.put(cqEntry.cqId, cqEntry);
     }
   }
@@ -527,7 +535,8 @@ private void serialize(OutputStream stream) throws IOException {
       ReadWriteIOUtils.write(nextOccurrenceIndex, stream);
     }
 
-    private static CQEntry deserialize(InputStream stream, boolean structured) throws IOException {
+    private static CQEntry deserialize(
+        InputStream stream, boolean structured, boolean hasOccurrenceIndex) throws IOException {
       String cqId = ReadWriteIOUtils.readString(stream);
       long everyInterval = ReadWriteIOUtils.readLong(stream);
       long boundaryTime = ReadWriteIOUtils.readLong(stream);
@@ -557,7 +566,7 @@ private static CQEntry deserialize(InputStream stream, boolean structured) throw
       boolean boundaryExplicit = structured && ReadWriteIOUtils.readBool(stream);
       CQState state = CQState.deserialize(ReadWriteIOUtils.readByte(stream));
       long lastExecutionTime = ReadWriteIOUtils.readLong(stream);
-      long nextOccurrenceIndex = structured ? ReadWriteIOUtils.readLong(stream) : -1;
+      long nextOccurrenceIndex = hasOccurrenceIndex ? ReadWriteIOUtils.readLong(stream) : -1;
       return new CQEntry(
           cqId,
           everyInterval,

iotdb-core/confignode/src/test/java/org/apache/iotdb/confignode/persistence/CQInfoTest.java

@@ -37,8 +37,11 @@
 
 import java.io.File;
 import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.nio.file.Files;
 import java.time.ZoneId;
 import java.time.ZonedDateTime;
+import java.util.Arrays;
 
 import static org.apache.iotdb.db.utils.constant.TestConstant.BASE_OUTPUT_PATH;
 
@@ -200,6 +203,49 @@ public void testOccurrenceIndexCasFencesOutOfOrderCallbacks() {
             .getCode());
   }
 
+  @Test
+  public void testPreviousStructuredSnapshotWithoutOccurrenceIndex() throws Exception {
+    File previousSnapshotDir = new File(BASE_OUTPUT_PATH, "snapshot-previous");
+    if (previousSnapshotDir.exists()) {
+      FileUtils.deleteDirectory(previousSnapshotDir);
+    }
+    previousSnapshotDir.mkdirs();
+
+    CQInfo source = new CQInfo();
+    TCreateCQReq req =
+        new TCreateCQReq(
+            "previousStructuredCq",
+            1000,
+            0,
+            1000,
+            0,
+            (byte) 0,
+            "select 1",
+            "create cq previousStructuredCq",
+            "UTC",
+            "root");
+    req.setDurationEncodingVersion((short) 1);
+    req.setEveryDuration(new TCQDuration(0, 1000));
+    req.setStartOffsetDuration(new TCQDuration(0, 1000));
+    req.setEndOffsetDuration(new TCQDuration(0, 0));
+    req.setBoundaryExplicit(true);
+    source.addCQ(new AddCQPlan(req, "previousStructuredToken", 1000));
+    source.processTakeSnapshot(previousSnapshotDir);
+
+    File snapshotFile = new File(previousSnapshotDir, "cq_info.snapshot");
+    byte[] snapshot = Files.readAllBytes(snapshotFile.toPath());
+    ByteBuffer.wrap(snapshot).putInt(-1842801);
+    // The -1842801 format predates nextOccurrenceIndex, which is the final field of each entry.
+    Files.write(snapshotFile.toPath(), Arrays.copyOf(snapshot, snapshot.length - Long.BYTES));
+
+    CQInfo restored = new CQInfo();
+    restored.processLoadSnapshot(previousSnapshotDir);
+    ShowCQResp restoredResponse = restored.showCQ(new ShowCQPlan("previousStructuredCq"));
+    Assert.assertEquals(1, restoredResponse.getCqList().size());
+    Assert.assertEquals(-1, restoredResponse.getCqList().get(0).getNextOccurrenceIndex());
+    FileUtils.deleteDirectory(previousSnapshotDir);
+  }
+
   @Test
   public void testCalendarOccurrenceProgressSurvivesSnapshotRecovery() throws Exception {
     ZoneId zone = ZoneId.of("UTC");