beyond1920 commented on a change in pull request #14905:
URL: https://github.com/apache/flink/pull/14905#discussion_r580098617
##########
File path:
flink-table/flink-table-runtime-blink/src/main/java/org/apache/flink/table/runtime/operators/window/slicing/SliceAssigners.java
##########
@@ -321,20 +322,15 @@ public void mergeSlices(long sliceEnd, MergeCallback
callback) throws Exception
private static final long serialVersionUID = 1L;
private final int windowEndIndex;
- private final long windowSize;
+ private final SliceAssigner innerAssigner;
private final ReusableListIterable reuseExpiredList = new
ReusableListIterable();
- public WindowedSliceAssigner(int windowEndIndex, long windowSize) {
+ public WindowedSliceAssigner(int windowEndIndex, SliceAssigner
innerAssigner) {
Review comment:
`innerAssigner ` seems to only be used to calculate window start?
Could we update constructor to pass windowStartIndex and windowEndIndex
because it's a little strange to create `SliceAssigner` based on
`Integer.MAX_VALUE` as `timeAttributeIndex` for
`WindowAttachedWindowingStrategy`,
##########
File path:
flink-table/flink-table-planner-blink/src/main/java/org/apache/flink/table/planner/plan/nodes/exec/stream/StreamExecWindowAggregate.java
##########
@@ -0,0 +1,270 @@
+/*
+ * 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.flink.table.planner.plan.nodes.exec.stream;
+
+import org.apache.flink.api.dag.Transformation;
+import org.apache.flink.streaming.api.operators.OneInputStreamOperator;
+import org.apache.flink.streaming.api.operators.SimpleOperatorFactory;
+import org.apache.flink.streaming.api.transformations.OneInputTransformation;
+import org.apache.flink.table.api.TableConfig;
+import org.apache.flink.table.api.TableException;
+import org.apache.flink.table.data.RowData;
+import
org.apache.flink.table.planner.calcite.FlinkRelBuilder.PlannerNamedWindowProperty;
+import org.apache.flink.table.planner.codegen.CodeGeneratorContext;
+import org.apache.flink.table.planner.codegen.agg.AggsHandlerCodeGenerator;
+import org.apache.flink.table.planner.delegation.PlannerBase;
+import org.apache.flink.table.planner.expressions.PlannerWindowProperty;
+import org.apache.flink.table.planner.plan.logical.CumulativeWindowSpec;
+import org.apache.flink.table.planner.plan.logical.HoppingWindowSpec;
+import
org.apache.flink.table.planner.plan.logical.TimeAttributeWindowingStrategy;
+import org.apache.flink.table.planner.plan.logical.TumblingWindowSpec;
+import
org.apache.flink.table.planner.plan.logical.WindowAttachedWindowingStrategy;
+import org.apache.flink.table.planner.plan.logical.WindowSpec;
+import org.apache.flink.table.planner.plan.logical.WindowingStrategy;
+import org.apache.flink.table.planner.plan.nodes.exec.ExecEdge;
+import org.apache.flink.table.planner.plan.nodes.exec.ExecNode;
+import org.apache.flink.table.planner.plan.nodes.exec.ExecNodeBase;
+import org.apache.flink.table.planner.plan.nodes.exec.InputProperty;
+import org.apache.flink.table.planner.plan.nodes.exec.utils.ExecNodeUtil;
+import org.apache.flink.table.planner.plan.utils.AggregateInfoList;
+import org.apache.flink.table.planner.plan.utils.AggregateUtil;
+import org.apache.flink.table.planner.plan.utils.KeySelectorUtil;
+import org.apache.flink.table.planner.utils.JavaScalaConversionUtil;
+import
org.apache.flink.table.runtime.generated.GeneratedNamespaceAggsHandleFunction;
+import org.apache.flink.table.runtime.keyselector.RowDataKeySelector;
+import
org.apache.flink.table.runtime.operators.aggregate.window.SlicingWindowAggOperatorBuilder;
+import org.apache.flink.table.runtime.operators.window.slicing.SliceAssigner;
+import org.apache.flink.table.runtime.operators.window.slicing.SliceAssigners;
+import
org.apache.flink.table.runtime.operators.window.slicing.SliceSharedAssigner;
+import org.apache.flink.table.runtime.types.LogicalTypeDataTypeConverter;
+import org.apache.flink.table.runtime.typeutils.InternalTypeInfo;
+import org.apache.flink.table.types.DataType;
+import org.apache.flink.table.types.logical.LogicalType;
+import org.apache.flink.table.types.logical.RowType;
+
+import org.apache.calcite.rel.core.AggregateCall;
+import org.apache.calcite.tools.RelBuilder;
+
+import java.time.Duration;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+
+/**
+ * Stream {@link ExecNode} for window table-valued based aggregate.
+ *
+ * <p>The differences between {@link StreamExecWindowAggregate} and {@link
+ * StreamExecGroupWindowAggregate} is that, this node is translated from
window TVF syntax, but the
+ * other is from the legacy GROUP WINDOW FUNCTION syntax. In the long future,
{@link
+ * StreamExecGroupWindowAggregate} will be dropped.
+ */
+public class StreamExecWindowAggregate extends ExecNodeBase<RowData>
+ implements StreamExecNode<RowData> {
+
+ private static final long WINDOW_AGG_MEMORY_RATIO = 100;
+
+ private final int[] grouping;
+ private final AggregateCall[] aggCalls;
+ private final WindowingStrategy windowing;
+ private final PlannerNamedWindowProperty[] namedWindowProperties;
+
+ public StreamExecWindowAggregate(
+ int[] grouping,
+ AggregateCall[] aggCalls,
+ WindowingStrategy windowing,
+ PlannerNamedWindowProperty[] namedWindowProperties,
+ InputProperty inputProperty,
+ RowType outputType,
+ String description) {
+ super(Collections.singletonList(inputProperty), outputType,
description);
+ this.grouping = grouping;
+ this.aggCalls = aggCalls;
+ this.windowing = windowing;
+ this.namedWindowProperties = namedWindowProperties;
+ }
+
+ @SuppressWarnings("unchecked")
+ @Override
+ protected Transformation<RowData> translateToPlanInternal(PlannerBase
planner) {
+ final ExecEdge inputEdge = getInputEdges().get(0);
+ final Transformation<RowData> inputTransform =
+ (Transformation<RowData>) inputEdge.translateToPlan(planner);
+ final RowType inputRowType = (RowType) inputEdge.getOutputType();
+
+ final TableConfig config = planner.getTableConfig();
+ final SliceAssigner sliceAssigner = createSliceAssigner(windowing);
+
+ // Hopping window requires additional COUNT(*) to determine whether to
register next timer
+ // through whether the current fired window is empty, see
SliceSharedWindowAggProcessor.
+ final boolean needInputCount = sliceAssigner instanceof
SliceAssigners.HoppingSliceAssigner;
+ final boolean[] aggCallNeedRetractions = new boolean[aggCalls.length];
+ Arrays.fill(aggCallNeedRetractions, false);
+ final AggregateInfoList aggInfoList =
+ AggregateUtil.transformToStreamAggregateInfoList(
+ inputRowType,
+
JavaScalaConversionUtil.toScala(Arrays.asList(aggCalls)),
+ aggCallNeedRetractions,
+ needInputCount,
+ true, // isStateBackendDataViews
+ true); // needDistinctInfo
+
+ final GeneratedNamespaceAggsHandleFunction<Long> generatedAggsHandler =
+ createAggsHandler(
+ sliceAssigner,
+ aggInfoList,
+ config,
+ planner.getRelBuilder(),
+ inputRowType.getChildren());
+
+ final LogicalType[] keyTypes =
+ Arrays.stream(grouping)
+ .mapToObj(inputRowType::getTypeAt)
+ .toArray(LogicalType[]::new);
+ final LogicalType[] accTypes =
convertToLogicalTypes(aggInfoList.getAccTypes());
+
+ final OneInputStreamOperator<RowData, RowData> windowOperator =
+ SlicingWindowAggOperatorBuilder.builder()
+ .inputType(inputRowType)
+ .keyTypes(keyTypes)
+ .assigner(sliceAssigner)
+ .countStarIndex(aggInfoList.getIndexOfCountStar())
+ .aggregate(generatedAggsHandler, accTypes)
+ .build();
+
+ final OneInputTransformation<RowData, RowData> transform =
+ ExecNodeUtil.createOneInputTransformation(
+ inputTransform,
+ getDescription(),
+ SimpleOperatorFactory.of(windowOperator),
+ InternalTypeInfo.of(getOutputType()),
+ inputTransform.getParallelism(),
+ WINDOW_AGG_MEMORY_RATIO);
+
+ if (inputsContainSingleton()) {
+ transform.setParallelism(1);
+ transform.setMaxParallelism(1);
+ }
+
+ // set KeyType and Selector for state
+ final RowDataKeySelector selector =
+ KeySelectorUtil.getRowDataSelector(grouping,
InternalTypeInfo.of(inputRowType));
+ transform.setStateKeySelector(selector);
+ transform.setStateKeyType(selector.getProducedType());
+ return transform;
+ }
+
+ private GeneratedNamespaceAggsHandleFunction<Long> createAggsHandler(
+ SliceAssigner sliceAssigner,
+ AggregateInfoList aggInfoList,
+ TableConfig config,
+ RelBuilder relBuilder,
+ List<LogicalType> fieldTypes) {
+ final AggsHandlerCodeGenerator generator =
+ new AggsHandlerCodeGenerator(
+ new CodeGeneratorContext(config),
+ relBuilder,
+ JavaScalaConversionUtil.toScala(fieldTypes),
+ false) // copyInputField
+ .needAccumulate();
+
+ if (sliceAssigner instanceof SliceSharedAssigner) {
+ generator.needMerge(0, false, null);
+ }
+
+ final List<PlannerWindowProperty> windowProperties =
+ Arrays.asList(
+ Arrays.stream(namedWindowProperties)
+ .map(PlannerNamedWindowProperty::property)
+ .toArray(PlannerWindowProperty[]::new));
+
+ return generator.generateNamespaceAggsHandler(
+ "GroupingWindowAggsHandler",
+ aggInfoList,
+ JavaScalaConversionUtil.toScala(windowProperties),
+ sliceAssigner);
+ }
+
+ //
------------------------------------------------------------------------------------------
+ // Utilities
+ //
------------------------------------------------------------------------------------------
+
+ private static SliceAssigner createSliceAssigner(WindowingStrategy
windowingStrategy) {
+ WindowSpec windowSpec = windowingStrategy.window();
+ if (windowingStrategy instanceof WindowAttachedWindowingStrategy) {
+ int windowEndIndex = ((WindowAttachedWindowingStrategy)
windowingStrategy).windowEnd();
+ // we don't need time attribute to assign windows, use a magic
value in this case
+ SliceAssigner innerAssigner = createSliceAssigner(windowSpec,
Integer.MAX_VALUE);
+ return SliceAssigners.windowed(windowEndIndex, innerAssigner);
Review comment:
It's a little strange to create SliceAssigner based on
`Integer.MAX_VALUE` as timeAttributeIdx, could we just pass `windowStartIndex`
and `windowEndIndex ` when call `SliceAssigners.windowed(`?
##########
File path:
flink-table/flink-table-planner-blink/src/main/scala/org/apache/flink/table/planner/plan/nodes/physical/stream/StreamPhysicalWindowAggregate.scala
##########
@@ -0,0 +1,137 @@
+/*
+ * 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.flink.table.planner.plan.nodes.physical.stream
+
+import org.apache.flink.table.api.TableException
+import
org.apache.flink.table.planner.calcite.FlinkRelBuilder.PlannerNamedWindowProperty
+import org.apache.flink.table.planner.calcite.FlinkTypeFactory
+import org.apache.flink.table.planner.expressions.{PlannerProctimeAttribute,
PlannerRowtimeAttribute, PlannerWindowEnd, PlannerWindowStart}
+import org.apache.flink.table.planner.plan.logical.WindowingStrategy
+import org.apache.flink.table.planner.plan.nodes.exec.{ExecNode, InputProperty}
+import
org.apache.flink.table.planner.plan.nodes.exec.stream.StreamExecWindowAggregate
+import org.apache.flink.table.planner.plan.utils.{FlinkRelOptUtil,
RelExplainUtil}
+import
org.apache.flink.table.planner.plan.utils.WindowEmitStrategy.{TABLE_EXEC_EMIT_EARLY_FIRE_ENABLED,
TABLE_EXEC_EMIT_LATE_FIRE_ENABLED}
+import org.apache.flink.table.types.logical.utils.LogicalTypeUtils
+
+import org.apache.calcite.plan.{RelOptCluster, RelTraitSet}
+import org.apache.calcite.rel.`type`.RelDataType
+import org.apache.calcite.rel.core.{Aggregate, AggregateCall}
+import org.apache.calcite.rel.{RelNode, RelWriter, SingleRel}
+import org.apache.calcite.util.ImmutableBitSet
+
+import java.util
+import java.util.Collections
+
+import scala.collection.JavaConverters._
+
+/**
+ * Streaming window aggregate physical node which will be translate to window
aggregate operator.
+ *
+ * Note: The differences between [[StreamPhysicalWindowAggregate]] and
+ * [[StreamPhysicalGroupWindowAggregate]] is that,
[[StreamPhysicalWindowAggregate]] is translated
+ * from window TVF syntax, but the other is from the legacy GROUP WINDOW
FUNCTION syntax.
+ * In the long future, [[StreamPhysicalGroupWindowAggregate]] will be dropped.
+ */
+class StreamPhysicalWindowAggregate(
+ cluster: RelOptCluster,
+ traitSet: RelTraitSet,
+ inputRel: RelNode,
+ val grouping: Array[Int],
+ val aggCalls: Seq[AggregateCall],
+ val windowing: WindowingStrategy,
+ val namedWindowProperties: Seq[PlannerNamedWindowProperty])
+ extends SingleRel(cluster, traitSet, inputRel)
+ with StreamPhysicalRel {
+
+ override def requireWatermark: Boolean = windowing.isRowtime
+
+ override def deriveRowType(): RelDataType = {
+ val groupSet = ImmutableBitSet.of(grouping: _*)
+ val baseType = Aggregate.deriveRowType(
+ cluster.getTypeFactory,
+ getInput.getRowType,
+ false,
+ groupSet,
+ Collections.singletonList(groupSet),
+ aggCalls.asJava)
+ val typeFactory = getCluster.getTypeFactory.asInstanceOf[FlinkTypeFactory]
+ val builder = typeFactory.builder
+ builder.addAll(baseType.getFieldList)
+ namedWindowProperties.foreach { namedProp =>
+ // use types from windowing strategy which keeps the precision and
timestamp type
+ // cast the type to not null type, because window properties should
never be null
+ val timeType = namedProp.property match {
+ case PlannerWindowStart(_) | PlannerWindowEnd(_) =>
+
LogicalTypeUtils.removeTimeAttributes(windowing.timeAttributeType).copy(false)
+ case PlannerRowtimeAttribute(_) | PlannerProctimeAttribute(_) =>
+ windowing.timeAttributeType.copy(false)
+ }
+ builder.add(namedProp.name,
typeFactory.createFieldTypeFromLogicalType(timeType))
+ }
+ builder.build()
+ }
+
+ override def explainTerms(pw: RelWriter): RelWriter = {
+ val inputRowType = getInput.getRowType
+ val inputFieldNames = inputRowType.getFieldNames.asScala.toArray
+ super.explainTerms(pw)
+ .itemIf("groupBy", RelExplainUtil.fieldToString(grouping, inputRowType),
grouping.nonEmpty)
+ .item("window", windowing.toSummaryString(inputFieldNames))
+ .item("select", RelExplainUtil.streamWindowAggregationToString(
+ inputRowType,
+ grouping,
+ getRowType,
+ aggCalls,
+ namedWindowProperties))
+ }
+
+ override def copy(
+ traitSet: RelTraitSet,
+ inputs: util.List[RelNode]): RelNode = {
+ new StreamPhysicalWindowAggregate(
+ cluster,
+ traitSet,
+ inputs.get(0),
+ grouping,
+ aggCalls,
+ windowing,
+ namedWindowProperties
+ )
+ }
+
+ override def translateToExecNode(): ExecNode[_] = {
+ val conf = FlinkRelOptUtil.getTableConfigFromContext(this).getConfiguration
+ if (conf.getBoolean(TABLE_EXEC_EMIT_EARLY_FIRE_ENABLED) ||
+ conf.getBoolean(TABLE_EXEC_EMIT_LATE_FIRE_ENABLED)) {
+ throw new TableException("Currently, window table function based
aggregate doesn't " +
+ s"support early-fire and late-fire configuration " +
+ s"'${TABLE_EXEC_EMIT_EARLY_FIRE_ENABLED.key()}' and " +
+ s"'${TABLE_EXEC_EMIT_LATE_FIRE_ENABLED.key()}'.")
+ }
+ new StreamExecWindowAggregate(
Review comment:
It's better to add check for allow lateness it seems not to be supported
yet.
##########
File path:
flink-table/flink-table-planner-blink/src/main/java/org/apache/flink/table/planner/plan/nodes/exec/stream/StreamExecWindowAggregate.java
##########
@@ -0,0 +1,270 @@
+/*
+ * 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.flink.table.planner.plan.nodes.exec.stream;
+
+import org.apache.flink.api.dag.Transformation;
+import org.apache.flink.streaming.api.operators.OneInputStreamOperator;
+import org.apache.flink.streaming.api.operators.SimpleOperatorFactory;
+import org.apache.flink.streaming.api.transformations.OneInputTransformation;
+import org.apache.flink.table.api.TableConfig;
+import org.apache.flink.table.api.TableException;
+import org.apache.flink.table.data.RowData;
+import
org.apache.flink.table.planner.calcite.FlinkRelBuilder.PlannerNamedWindowProperty;
+import org.apache.flink.table.planner.codegen.CodeGeneratorContext;
+import org.apache.flink.table.planner.codegen.agg.AggsHandlerCodeGenerator;
+import org.apache.flink.table.planner.delegation.PlannerBase;
+import org.apache.flink.table.planner.expressions.PlannerWindowProperty;
+import org.apache.flink.table.planner.plan.logical.CumulativeWindowSpec;
+import org.apache.flink.table.planner.plan.logical.HoppingWindowSpec;
+import
org.apache.flink.table.planner.plan.logical.TimeAttributeWindowingStrategy;
+import org.apache.flink.table.planner.plan.logical.TumblingWindowSpec;
+import
org.apache.flink.table.planner.plan.logical.WindowAttachedWindowingStrategy;
+import org.apache.flink.table.planner.plan.logical.WindowSpec;
+import org.apache.flink.table.planner.plan.logical.WindowingStrategy;
+import org.apache.flink.table.planner.plan.nodes.exec.ExecEdge;
+import org.apache.flink.table.planner.plan.nodes.exec.ExecNode;
+import org.apache.flink.table.planner.plan.nodes.exec.ExecNodeBase;
+import org.apache.flink.table.planner.plan.nodes.exec.InputProperty;
+import org.apache.flink.table.planner.plan.nodes.exec.utils.ExecNodeUtil;
+import org.apache.flink.table.planner.plan.utils.AggregateInfoList;
+import org.apache.flink.table.planner.plan.utils.AggregateUtil;
+import org.apache.flink.table.planner.plan.utils.KeySelectorUtil;
+import org.apache.flink.table.planner.utils.JavaScalaConversionUtil;
+import
org.apache.flink.table.runtime.generated.GeneratedNamespaceAggsHandleFunction;
+import org.apache.flink.table.runtime.keyselector.RowDataKeySelector;
+import
org.apache.flink.table.runtime.operators.aggregate.window.SlicingWindowAggOperatorBuilder;
+import org.apache.flink.table.runtime.operators.window.slicing.SliceAssigner;
+import org.apache.flink.table.runtime.operators.window.slicing.SliceAssigners;
+import
org.apache.flink.table.runtime.operators.window.slicing.SliceSharedAssigner;
+import org.apache.flink.table.runtime.types.LogicalTypeDataTypeConverter;
+import org.apache.flink.table.runtime.typeutils.InternalTypeInfo;
+import org.apache.flink.table.types.DataType;
+import org.apache.flink.table.types.logical.LogicalType;
+import org.apache.flink.table.types.logical.RowType;
+
+import org.apache.calcite.rel.core.AggregateCall;
+import org.apache.calcite.tools.RelBuilder;
+
+import java.time.Duration;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+
+/**
+ * Stream {@link ExecNode} for window table-valued based aggregate.
+ *
+ * <p>The differences between {@link StreamExecWindowAggregate} and {@link
+ * StreamExecGroupWindowAggregate} is that, this node is translated from
window TVF syntax, but the
+ * other is from the legacy GROUP WINDOW FUNCTION syntax. In the long future,
{@link
+ * StreamExecGroupWindowAggregate} will be dropped.
+ */
+public class StreamExecWindowAggregate extends ExecNodeBase<RowData>
+ implements StreamExecNode<RowData> {
+
+ private static final long WINDOW_AGG_MEMORY_RATIO = 100;
+
+ private final int[] grouping;
+ private final AggregateCall[] aggCalls;
+ private final WindowingStrategy windowing;
+ private final PlannerNamedWindowProperty[] namedWindowProperties;
+
+ public StreamExecWindowAggregate(
+ int[] grouping,
+ AggregateCall[] aggCalls,
+ WindowingStrategy windowing,
+ PlannerNamedWindowProperty[] namedWindowProperties,
+ InputProperty inputProperty,
+ RowType outputType,
+ String description) {
+ super(Collections.singletonList(inputProperty), outputType,
description);
+ this.grouping = grouping;
+ this.aggCalls = aggCalls;
+ this.windowing = windowing;
+ this.namedWindowProperties = namedWindowProperties;
+ }
+
+ @SuppressWarnings("unchecked")
+ @Override
+ protected Transformation<RowData> translateToPlanInternal(PlannerBase
planner) {
+ final ExecEdge inputEdge = getInputEdges().get(0);
+ final Transformation<RowData> inputTransform =
+ (Transformation<RowData>) inputEdge.translateToPlan(planner);
+ final RowType inputRowType = (RowType) inputEdge.getOutputType();
+
+ final TableConfig config = planner.getTableConfig();
+ final SliceAssigner sliceAssigner = createSliceAssigner(windowing);
+
+ // Hopping window requires additional COUNT(*) to determine whether to
register next timer
+ // through whether the current fired window is empty, see
SliceSharedWindowAggProcessor.
+ final boolean needInputCount = sliceAssigner instanceof
SliceAssigners.HoppingSliceAssigner;
Review comment:
Could you please explain why need COUNT(*) for HoppingSliceAssigner in
detail, I'm still confused about this. Thanks a lot.
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