HeartSaVioR commented on a change in pull request #31495:
URL: https://github.com/apache/spark/pull/31495#discussion_r571850667



##########
File path: 
sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/HDFSMetadataLog.scala
##########
@@ -239,18 +239,35 @@ class HDFSMetadataLog[T <: AnyRef : 
ClassTag](sparkSession: SparkSession, path:
       .reverse
   }
 
+  private var lastPurgedBatchId: Long = -1L
+
   /**
    * Removes all the log entry earlier than thresholdBatchId (exclusive).
    */
   override def purge(thresholdBatchId: Long): Unit = {
-    val batchIds = fileManager.list(metadataPath, batchFilesFilter)
-      .map(f => pathToBatchId(f.getPath))
-
-    for (batchId <- batchIds if batchId < thresholdBatchId) {
-      val path = batchIdToPath(batchId)
-      fileManager.delete(path)
-      logTrace(s"Removed metadata log file: $path")
+    val possibleTargetBatchIds = (lastPurgedBatchId + 1 until thresholdBatchId)
+    if (possibleTargetBatchIds.length <= 3) {
+      // avoid using list if we only need to purge at most 3 elements
+      possibleTargetBatchIds.foreach { batchId =>
+        val path = batchIdToPath(batchId)
+        if (fileManager.exists(path)) {

Review comment:
       I thought about this a bit more, and I admit I was wrong about the 
assumption; log file may not be existed. It could be for some batches after 
restarting from checkpoint, but once the query runs more than the threshold 
(100 batches by default), the log file "should" exist.
   
   Thanks for raising this. Will make a change and run simple test before 
pushing.




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