[GitHub] [incubator-pinot] Jackie-Jiang commented on a change in pull request #5339: Add api in AggregationFunction to get its compiled input expressions.

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

Jackie-Jiang commented on a change in pull request #5339:
URL: https://github.com/apache/incubator-pinot/pull/5339#discussion_r421006375



##########
File path: pinot-core/src/main/java/org/apache/pinot/core/plan/TransformPlanNode.java
##########
@@ -43,76 +39,70 @@
 
   private final String _segmentName;
   private final ProjectionPlanNode _projectionPlanNode;
-  private final Set<String> _projectionColumns = new HashSet<>();
-  private final Set<TransformExpressionTree> _expressions = new HashSet<>();
+  private final Set<TransformExpressionTree> _expressions;
   private int _maxDocPerNextCall = DocIdSetPlanNode.MAX_DOC_PER_CALL;
 
-  public TransformPlanNode(IndexSegment indexSegment, BrokerRequest brokerRequest) {
+  public TransformPlanNode(IndexSegment indexSegment, BrokerRequest brokerRequest,
+      Set<TransformExpressionTree> expressionsToPlan) {
     _segmentName = indexSegment.getSegmentName();
-    extractColumnsAndTransforms(brokerRequest, indexSegment);
-    _projectionPlanNode = new ProjectionPlanNode(indexSegment, _projectionColumns,
+
+    setMaxDocsForSelection(brokerRequest);
+    Set<String> projectionColumns = new HashSet<>();
+    extractProjectionColumns(expressionsToPlan, projectionColumns);
+
+    _expressions = expressionsToPlan;
+    _projectionPlanNode = new ProjectionPlanNode(indexSegment, projectionColumns,
         new DocIdSetPlanNode(indexSegment, brokerRequest, _maxDocPerNextCall));
   }
 
+  private void extractProjectionColumns(Set<TransformExpressionTree> expressionsToPlan, Set<String> projectionColumns) {
+    for (TransformExpressionTree expression : expressionsToPlan) {
+      extractProjectionColumns(expression, projectionColumns);
+    }
+  }
+
+  private void extractProjectionColumns(TransformExpressionTree expression, Set<String> projectionColumns) {
+    TransformExpressionTree.ExpressionType expressionType = expression.getExpressionType();
+    switch (expressionType) {
+      case FUNCTION:
+        for (TransformExpressionTree child : expression.getChildren()) {
+          extractProjectionColumns(child, projectionColumns);
+        }
+        break;
+
+      case IDENTIFIER:
+        projectionColumns.add(expression.getValue());
+        break;
+
+      case LITERAL:
+        // Do nothing.
+        break;
+
+      default:
+        throw new UnsupportedOperationException("Unsupported expression type: " + expressionType);
+    }
+  }
+
   /**
-   * Helper method to extract projection columns and transform expressions from the given broker request.
+   * Helper method to set the max number of docs to return for selection queries
    */
-  private void extractColumnsAndTransforms(BrokerRequest brokerRequest, IndexSegment indexSegment) {
-    Set<String> columns = new HashSet<>();
-    if (brokerRequest.isSetAggregationsInfo()) {
-      // Extract aggregation expressions
-      for (AggregationInfo aggregationInfo : brokerRequest.getAggregationsInfo()) {
-        if (aggregationInfo.getAggregationType().equalsIgnoreCase(AggregationFunctionType.DISTINCT.getName())) {
-          // 'DISTINCT(col1, col2 ...)' is modeled as one single aggregation function
-          List<String> distinctColumns = AggregationFunctionUtils.getAggregationExpressions(aggregationInfo);
-          columns.addAll(distinctColumns);
-        } else if (!aggregationInfo.getAggregationType().equalsIgnoreCase(AggregationFunctionType.COUNT.getName())) {
-          columns.addAll(AggregationFunctionUtils.getAggregationExpressions(aggregationInfo));
-        }
-      }
-      // Extract group-by expressions
-      if (brokerRequest.isSetGroupBy()) {
-        columns.addAll(brokerRequest.getGroupBy().getExpressions());
-      }
-    } else {
+  private void setMaxDocsForSelection(BrokerRequest brokerRequest) {

Review comment:
       This logic should also be handle in the upper level (SelectionPlanNode) and passed to this class

##########
File path: pinot-core/src/main/java/org/apache/pinot/core/plan/TransformPlanNode.java
##########
@@ -43,76 +39,70 @@
 
   private final String _segmentName;
   private final ProjectionPlanNode _projectionPlanNode;
-  private final Set<String> _projectionColumns = new HashSet<>();
-  private final Set<TransformExpressionTree> _expressions = new HashSet<>();
+  private final Set<TransformExpressionTree> _expressions;
   private int _maxDocPerNextCall = DocIdSetPlanNode.MAX_DOC_PER_CALL;
 
-  public TransformPlanNode(IndexSegment indexSegment, BrokerRequest brokerRequest) {
+  public TransformPlanNode(IndexSegment indexSegment, BrokerRequest brokerRequest,
+      Set<TransformExpressionTree> expressionsToPlan) {

Review comment:
       (nit) `expressionsToPlan` -> `expressions`?
   
   Also pass `maxDocsPerBlock` from upper level?

##########
File path: pinot-core/src/main/java/org/apache/pinot/core/query/aggregation/function/AggregationFunction.java
##########
@@ -49,6 +51,13 @@
    */
   String getResultColumnName();
 
+  /**
+   * Returns a list of input expressions needed for performing aggregation.
+   *
+   * @return List of input expressions

Review comment:
       (nit) We don't have return argument documented in this file, maybe keep it consistent?

##########
File path: pinot-core/src/main/java/org/apache/pinot/core/query/aggregation/function/AggregationFunctionUtils.java
##########
@@ -182,4 +187,37 @@ public static String concatArgs(List<String> arguments) {
     return (arguments.size() > 1) ? String.join(CompilerConstants.AGGREGATION_FUNCTION_ARG_SEPARATOR, arguments)
         : arguments.get(0);
   }
+
+  /**
+   * Compiles and returns all transform expressions required for computing the aggregation, group-by
+   * and order-by
+   *
+   * @param brokerRequest Broker Request
+   * @param functionContexts Aggregation Function contexts
+   * @return Set of compiled expressions in the aggregation, group-by and order-by clauses
+   */
+  public static Set<TransformExpressionTree> collectExpressionsToTransform(BrokerRequest brokerRequest,
+      AggregationFunctionContext[] functionContexts) {
+
+    Set<TransformExpressionTree> expressionTrees = new LinkedHashSet<>();
+    for (AggregationFunctionContext functionContext : functionContexts) {
+      AggregationFunction function = functionContext.getAggregationFunction();
+
+      // Count is always treated as count(*) and does not need any columns to be projected.
+      if (!function.getType().equals(AggregationFunctionType.COUNT)) {

Review comment:
       No need to specialize this. Just make CountAggregationFunction return empty list

##########
File path: pinot-core/src/main/java/org/apache/pinot/core/query/aggregation/function/CountAggregationFunction.java
##########
@@ -57,6 +59,11 @@ public String getResultColumnName() {
     return AggregationFunctionType.COUNT.getName().toLowerCase() + "(*)";
   }
 
+  @Override
+  public List<TransformExpressionTree> getInputExpressions() {
+    return null;

Review comment:
       ```suggestion
       return Collections.emptyList();
   ```




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