[GitHub] [druid] aditya-r-m commented on a change in pull request #8719: GREATEST/LEAST post-aggregators in SQL

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aditya-r-m commented on a change in pull request #8719: GREATEST/LEAST post-aggregators in SQL
URL: https://github.com/apache/druid/pull/8719#discussion_r374614476
 
 

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 File path: sql/src/main/java/org/apache/druid/sql/calcite/aggregation/builtin/GreatestSqlAggregator.java
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+/*
+ * 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.druid.sql.calcite.aggregation.builtin;
+
+import org.apache.calcite.sql.SqlAggFunction;
+import org.apache.calcite.sql.SqlFunctionCategory;
+import org.apache.calcite.sql.SqlKind;
+import org.apache.calcite.sql.type.OperandTypes;
+import org.apache.calcite.sql.type.ReturnTypes;
+import org.apache.druid.java.util.common.ISE;
+import org.apache.druid.math.expr.ExprMacroTable;
+import org.apache.druid.query.aggregation.AggregatorFactory;
+import org.apache.druid.query.aggregation.DoubleMaxAggregatorFactory;
+import org.apache.druid.query.aggregation.LongMaxAggregatorFactory;
+import org.apache.druid.query.aggregation.PostAggregator;
+import org.apache.druid.query.aggregation.post.DoubleGreatestPostAggregator;
+import org.apache.druid.query.aggregation.post.LongGreatestPostAggregator;
+import org.apache.druid.segment.column.ValueType;
+
+import java.util.List;
+
+/**
+ * Calcite integration class for Greatest post aggregators of Long & Double types.
+ * It applies Max aggregators over the provided fields/expressions & combines their results via Field access post aggregators.
+ */
+public class GreatestSqlAggregator extends MultiColumnSqlAggregator
+{
+  private static final SqlAggFunction FUNCTION_INSTANCE = new GreatestSqlAggFunction();
+  private static final String NAME = "GREATEST";
+
+  @Override
+  public SqlAggFunction calciteFunction()
+  {
+    return FUNCTION_INSTANCE;
+  }
+
+  @Override
+  AggregatorFactory createAggregatorFactory(
+      ValueType valueType,
+      String prefixedName,
+      FieldInfo fieldInfo,
+      ExprMacroTable macroTable
+  )
+  {
+    final AggregatorFactory aggregatorFactory;
+    switch (valueType) {
+      case LONG:
+        aggregatorFactory = new LongMaxAggregatorFactory(prefixedName, fieldInfo.fieldName, fieldInfo.expression, macroTable);
+        break;
+      case FLOAT:
+      case DOUBLE:
+        aggregatorFactory = new DoubleMaxAggregatorFactory(prefixedName, fieldInfo.fieldName, fieldInfo.expression, macroTable);
+        break;
+      default:
+        throw new ISE("Cannot create aggregator factory for type[%s]", valueType);
+    }
+    return aggregatorFactory;
+  }
+
+  @Override
+  PostAggregator createFinalPostAggregator(
+      ValueType valueType,
+      String name,
+      List<PostAggregator> postAggregators
+  )
+  {
+    final PostAggregator finalPostAggregator;
+    switch (valueType) {
+      case LONG:
+        finalPostAggregator = new LongGreatestPostAggregator(name, postAggregators);
+        break;
+      case FLOAT:
+      case DOUBLE:
+        finalPostAggregator = new DoubleGreatestPostAggregator(name, postAggregators);
+        break;
+      default:
+        throw new ISE("Cannot create aggregator factory for type[%s]", valueType);
+    }
+    return finalPostAggregator;
+  }
+
+  private static class GreatestSqlAggFunction extends SqlAggFunction
+  {
+    GreatestSqlAggFunction()
 
 Review comment:
   added the newly required param.

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