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jiangtian pushed a commit to branch modify_comment_version_controller
in repository https://gitbox.apache.org/repos/asf/iotdb.git

commit 224d6980084e60aaf5456523583da6b7e158db66
Author: jt <[email protected]>
AuthorDate: Fri Oct 23 09:59:24 2020 +0800

    update comment of VersionController
---
 .../org/apache/iotdb/db/engine/version/VersionController.java     | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git 
a/server/src/main/java/org/apache/iotdb/db/engine/version/VersionController.java
 
b/server/src/main/java/org/apache/iotdb/db/engine/version/VersionController.java
index c7faf3e..fc02314 100644
--- 
a/server/src/main/java/org/apache/iotdb/db/engine/version/VersionController.java
+++ 
b/server/src/main/java/org/apache/iotdb/db/engine/version/VersionController.java
@@ -20,7 +20,13 @@
 package org.apache.iotdb.db.engine.version;
 
 /**
- * VersionController controls the version(a monotonic increasing long) of a 
FileNode.
+ * VersionController manages the version(a monotonically increasing long) of a 
storage group. We
+ * define that each memtable flush, data deletion, or data update will 
generate a new version of
+ * dataset. So upon the above actions are performed, a new version number is 
generated and
+ * assigned to such actions.
+ * Additionally, we also assign versions to TsFiles in their file names, so 
hopefully we will
+ * compare files directly across IoTDB replicas.
+ * NOTICE: Thread-safety should be guaranteed by the caller.
  */
 public interface VersionController {
   /**

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