[GitHub] [rocketmq] drpmma commented on a diff in pull request #5606: [ISSUE #5605]Introduce tag estimation for lag calculation

[GitBox <gi...@apache.org>]

drpmma commented on code in PR #5606:
URL: https://github.com/apache/rocketmq/pull/5606#discussion_r1034253157


##########
store/src/main/java/org/apache/rocketmq/store/ConsumeQueue.java:
##########
@@ -1001,4 +1000,88 @@ public void swapMap(int reserveNum, long forceSwapIntervalMs, long normalSwapInt
     public void cleanSwappedMap(long forceCleanSwapIntervalMs) {
         mappedFileQueue.cleanSwappedMap(forceCleanSwapIntervalMs);
     }
+
+    @Override
+    public long estimateMessageCount(long from, long to, MessageFilter filter) {
+        long physicalOffsetFrom = from * CQ_STORE_UNIT_SIZE;
+        long physicalOffsetTo = to * CQ_STORE_UNIT_SIZE;
+        List<MappedFile> mappedFiles = mappedFileQueue.range(physicalOffsetFrom, physicalOffsetTo);
+        if (mappedFiles.isEmpty()) {
+            return -1;
+        }
+
+        boolean sample = false;
+        long match = 0;
+        long raw = 0;
+
+        for (MappedFile mappedFile : mappedFiles) {
+            int start = 0;
+            int len = mappedFile.getFileSize();
+            // First file segment
+            if (mappedFile.getFileFromOffset() <= physicalOffsetFrom) {
+                start = (int) (physicalOffsetFrom - mappedFile.getFileFromOffset());
+                if (mappedFile.getFileFromOffset() + mappedFile.getFileSize() >= physicalOffsetTo) {
+                    // Current mapped file covers search range completely.
+                    len = (int) (physicalOffsetTo - physicalOffsetFrom);
+                } else {
+                    len = mappedFile.getFileSize() - start;
+                }
+            }
+
+            // Scan partial of the last file segment
+            if (0 == start && mappedFile.getFileFromOffset() + mappedFile.getFileSize() > physicalOffsetTo) {
+                len = (int) (physicalOffsetTo - mappedFile.getFileFromOffset());
+            }
+

Review Comment:
   Maybe more annotation for readability.



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