[GitHub] [pinot] agavra commented on a diff in pull request #10006: [refactor] combine operator API changes

[GitBox <gi...@apache.org>]

agavra commented on code in PR #10006:
URL: https://github.com/apache/pinot/pull/10006#discussion_r1052650102


##########
pinot-core/src/main/java/org/apache/pinot/core/operator/combine/function/CombineFunction.java:
##########
@@ -0,0 +1,32 @@
+package org.apache.pinot.core.operator.combine.function;
+
+import org.apache.pinot.core.operator.blocks.results.BaseResultsBlock;
+
+
+public interface CombineFunction<T extends BaseResultsBlock> {
+
+  /**
+   * Merges a results block into the main mergeable results block.
+   * <p>NOTE: {@code blockToMerge} should contain the result for a segment without any exception. The errored segment
+   * result is already handled.
+   *
+   * @param mergedBlock The block that accumulates previous results. It should be modified to add the information of the
+   *                    other block.
+   * @param blockToMerge The new block that needs to be merged into the mergedBlock.
+   */
+  void mergeResultsBlocks(T mergedBlock, T blockToMerge);
+
+  /**
+   * Can be overridden for early termination. The input results block might not be mergeable.
+   */
+  default boolean isQuerySatisfied(T resultsBlock) {

Review Comment:
   nit: consider naming this `shouldEarlyTerminate`?



##########
pinot-core/src/main/java/org/apache/pinot/core/operator/combine/function/CombineFunction.java:
##########
@@ -0,0 +1,32 @@
+package org.apache.pinot.core.operator.combine.function;
+
+import org.apache.pinot.core.operator.blocks.results.BaseResultsBlock;
+
+
+public interface CombineFunction<T extends BaseResultsBlock> {
+
+  /**
+   * Merges a results block into the main mergeable results block.
+   * <p>NOTE: {@code blockToMerge} should contain the result for a segment without any exception. The errored segment
+   * result is already handled.
+   *
+   * @param mergedBlock The block that accumulates previous results. It should be modified to add the information of the
+   *                    other block.
+   * @param blockToMerge The new block that needs to be merged into the mergedBlock.
+   */
+  void mergeResultsBlocks(T mergedBlock, T blockToMerge);
+
+  /**
+   * Can be overridden for early termination. The input results block might not be mergeable.
+   */
+  default boolean isQuerySatisfied(T resultsBlock) {
+    return false;
+  }
+
+  /**
+   * Converts the given results block into a mergeable results block if necessary.
+   */
+  default T convertToMergeableBlock(T resultsBlock) {

Review Comment:
   unclear if this is called once per `mergeResultsBlocks` or once at the very end. it would be nice to clarify that in the comment



##########
pinot-core/src/main/java/org/apache/pinot/core/operator/combine/BaseSingleBlockCombineOperator.java:
##########
@@ -0,0 +1,139 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.pinot.core.operator.combine;
+
+import java.util.List;
+import java.util.concurrent.BlockingQueue;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.LinkedBlockingQueue;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicLong;
+import org.apache.pinot.core.common.Operator;
+import org.apache.pinot.core.operator.AcquireReleaseColumnsSegmentOperator;
+import org.apache.pinot.core.operator.blocks.results.BaseResultsBlock;
+import org.apache.pinot.core.operator.blocks.results.ExceptionResultsBlock;
+import org.apache.pinot.core.operator.combine.function.CombineFunction;
+import org.apache.pinot.core.query.request.context.QueryContext;
+
+
+/**
+ * Base implementation of the combine operator.
+ * <p>Combine operator uses multiple worker threads to process segments in parallel, and uses the main thread to merge
+ * the results blocks from the processed segments. It can early-terminate the query to save the system resources if it
+ * detects that the merged results can already satisfy the query, or the query is already errored out or timed out.
+ */
+@SuppressWarnings({"rawtypes", "unchecked"})
+public abstract class BaseSingleBlockCombineOperator<T extends BaseResultsBlock>

Review Comment:
   is this is called `SingleBlock` because it produces only a single block at the end? (as opposed to streaming, which might produce multiple?)



##########
pinot-core/src/main/java/org/apache/pinot/core/operator/combine/function/CombineFunction.java:
##########
@@ -0,0 +1,32 @@
+package org.apache.pinot.core.operator.combine.function;
+
+import org.apache.pinot.core.operator.blocks.results.BaseResultsBlock;
+
+
+public interface CombineFunction<T extends BaseResultsBlock> {
+
+  /**
+   * Merges a results block into the main mergeable results block.
+   * <p>NOTE: {@code blockToMerge} should contain the result for a segment without any exception. The errored segment

Review Comment:
   this note is a little confusing, are you suggesting that `blockToMerge` should not have an exception so that the implementor of this method does not need to worry about checking whether or not the block has an exception in the metadata?



##########
pinot-core/src/main/java/org/apache/pinot/core/operator/combine/BaseCombineOperator.java:
##########
@@ -54,7 +52,8 @@
  * detects that the merged results can already satisfy the query, or the query is already errored out or timed out.
  */
 @SuppressWarnings({"rawtypes", "unchecked"})
-public abstract class BaseCombineOperator<T extends BaseResultsBlock> extends BaseOperator<BaseResultsBlock> {

Review Comment:
   is the `_blockingQueue` held in this class still used anywhere?



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