[ROCKETMQ-270] Move flush position forward to first MappedFile whose start offset is non-zero.

store/src/main/java/org/apache/rocketmq/store/MappedFileQueue.java

@@ -421,7 +421,7 @@ public class MappedFileQueue {
 
     public boolean flush(final int flushLeastPages) {
         boolean result = true;
-        MappedFile mappedFile = this.findMappedFileByOffset(this.flushedWhere, false);
+        MappedFile mappedFile = this.findMappedFileByOffset(this.flushedWhere, this.flushedWhere == 0);
         if (mappedFile != null) {
             long tmpTimeStamp = mappedFile.getStoreTimestamp();
             int offset = mappedFile.flush(flushLeastPages);
@@ -438,7 +438,7 @@ public class MappedFileQueue {
 
     public boolean commit(final int commitLeastPages) {
         boolean result = true;
-        MappedFile mappedFile = this.findMappedFileByOffset(this.committedWhere, false);
+        MappedFile mappedFile = this.findMappedFileByOffset(this.committedWhere, this.committedWhere == 0);
         if (mappedFile != null) {
             int offset = mappedFile.commit(commitLeastPages);
             long where = mappedFile.getFileFromOffset() + offset;

store/src/test/java/org/apache/rocketmq/store/MappedFileQueueTest.java

@@ -20,9 +20,7 @@ package org.apache.rocketmq.store;
 import java.io.File;
 import java.nio.ByteBuffer;
 import java.util.Arrays;
-
 import org.apache.rocketmq.common.UtilAll;
-import org.apache.rocketmq.store.config.MessageStoreConfig;
 import org.junit.After;
 import org.junit.Test;
 
@@ -47,7 +45,7 @@ public class MappedFileQueueTest {
     }
 
     @Test
-    public void test_findMappedFileByOffset() {
+    public void testFindMappedFileByOffset() {
         // four-byte string.
         final String fixedMsg = "abcd";
 
@@ -97,6 +95,28 @@ public class MappedFileQueueTest {
         mappedFileQueue.destroy();
     }
 
+    @Test
+    public void testFindMappedFileByOffset_StartOffsetIsNonZero() {
+        MappedFileQueue mappedFileQueue =
+            new MappedFileQueue("target/unit_test_store/b/", 1024, null);
+
+        //Start from a non-zero offset
+        MappedFile mappedFile = mappedFileQueue.getLastMappedFile(1024);
+        assertThat(mappedFile).isNotNull();
+
+        assertThat(mappedFileQueue.findMappedFileByOffset(1025)).isEqualTo(mappedFile);
+
+        assertThat(mappedFileQueue.findMappedFileByOffset(0)).isNull();
+        assertThat(mappedFileQueue.findMappedFileByOffset(123, false)).isNull();
+        assertThat(mappedFileQueue.findMappedFileByOffset(123, true)).isEqualTo(mappedFile);
+
+        assertThat(mappedFileQueue.findMappedFileByOffset(0, false)).isNull();
+        assertThat(mappedFileQueue.findMappedFileByOffset(0, true)).isEqualTo(mappedFile);
+
+        mappedFileQueue.shutdown(1000);
+        mappedFileQueue.destroy();
+    }
+
     @Test
     public void testAppendMessage() {
         final String fixedMsg = "0123456789abcdef";