[GitHub] [spark] anishshri-db commented on a diff in pull request #41099: [SPARK-43421][SS] Implement Changelog based Checkpointing for RocksDB State Store Provider

["anishshri-db (via GitHub)" <gi...@apache.org>]

anishshri-db commented on code in PR #41099:
URL: https://github.com/apache/spark/pull/41099#discussion_r1190239700


##########
sql/catalyst/src/main/scala/org/apache/spark/sql/internal/SQLConf.scala:
##########
@@ -1940,6 +1940,15 @@ object SQLConf {
       // 5 is the default table format version for RocksDB 6.20.3.
       .createWithDefault(5)
 
+  val STATE_STORE_ROCKSDB_CHANGE_CHECKPOINTING_ENABLED =
+    buildConf("spark.sql.streaming.stateStore.rocksdb.enableChangelogCheckpointing")

Review Comment:
   Nit: maybe better to say `changelogCheckpoint.enabled` ?



##########
sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/state/RocksDB.scala:
##########
@@ -56,6 +56,15 @@ class RocksDB(
     hadoopConf: Configuration = new Configuration,
     loggingId: String = "") extends Logging {
 
+  case class RocksDBCheckpoint(checkpointDir: File, version: Long, numKeys: Long) {

Review Comment:
   Is case class preferred pattern for something like this ? cc - @HeartSaVioR 



##########
sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/state/RocksDB.scala:
##########
@@ -129,14 +140,15 @@ class RocksDB(
    * Note that this will copy all the necessary file from DFS to local disk as needed,
    * and possibly restart the native RocksDB instance.
    */
-  def load(version: Long): RocksDB = {
+  def load(version: Long, readOnly: Boolean = false): RocksDB = {
     assert(version >= 0)
     acquire()
     logInfo(s"Loading $version")
     try {
       if (loadedVersion != version) {
         closeDB()
-        val metadata = fileManager.loadCheckpointFromDfs(version, workingDir)
+        val latestSnapshotVersion = fileManager.getLatestSnapshotVersion(version)

Review Comment:
   Do we need this if changelog checkpoint is not enabled ?



##########
sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/state/RocksDB.scala:
##########
@@ -150,8 +162,27 @@ class RocksDB(
           metadata.numKeys
         }
         numKeysOnWritingVersion = numKeys
-        numKeysOnLoadedVersion = numKeys
-
+        // Replay change log from the last snapshot to the loaded version.
+        // This will be noop if changelog checkpointing is disabled.
+        for (v <- latestSnapshotVersion + 1 to version) {

Review Comment:
   Prefer to embed this in an if condition for easier readability 



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