[GitHub] [druid] cryptoe commented on a diff in pull request #13952: Limit the subquery results by memory usage

["cryptoe (via GitHub)" <gi...@apache.org>]

cryptoe commented on code in PR #13952:
URL: https://github.com/apache/druid/pull/13952#discussion_r1142035052


##########
server/src/main/java/org/apache/druid/server/ClientQuerySegmentWalker.java:
##########
@@ -577,25 +632,71 @@ private static <T, QueryType extends Query<T>> InlineDataSource toInlineDataSour
       );
     }
 
+    if (memoryLimitAccumulator.get() >= memoryLimitToUse) {
+      throw ResourceLimitExceededException.withMessage(
+          "Cannot issue subquery, maximum subquery result bytes[%d] reached",
+          memoryLimitToUse
+      );
+    }
+
     final RowSignature signature = toolChest.resultArraySignature(query);
 
-    final ArrayList<Object[]> resultList = new ArrayList<>();
+    final List<Object[]> resultList = toolChest.resultsAsArrays(query, results).toList();
 
-    toolChest.resultsAsArrays(query, results).accumulate(
-        resultList,
-        (acc, in) -> {
-          if (limitAccumulator.getAndIncrement() >= limitToUse) {
-            throw ResourceLimitExceededException.withMessage(
-                "Subquery generated results beyond maximum[%d]",
-                limitToUse
-            );
+    if (limitAccumulator.addAndGet(resultList.size()) >= limitToUse) {
+      throw ResourceLimitExceededException.withMessage(
+          "Subquery generated results beyond maximum[%d] rows",
+          limitToUse
+      );
+    }
+
+    Frame frame = null;
+
+    // Try to serialize the results into a frame only if the memory limit is set on the server or the query
+    if (memoryLimitSet) {

Review Comment:
   We should only serialize the frames only when memoryLimit Is set else the old code path should be invoked.  
   



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