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Subject [GitHub] [drill] vvysotskyi commented on a change in pull request #1736: DRILL-7064: Leverage the summary metadata for plain COUNT aggregates.
Date Sun, 07 Apr 2019 10:24:00 GMT
vvysotskyi commented on a change in pull request #1736: DRILL-7064: Leverage the summary metadata
for plain COUNT aggregates.
URL: https://github.com/apache/drill/pull/1736#discussion_r272826747
 
 

 ##########
 File path: exec/java-exec/src/main/java/org/apache/drill/exec/planner/common/CountToDirectScanUtils.java
 ##########
 @@ -0,0 +1,110 @@
+/*
+ * 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.drill.exec.planner.common;
+
+import org.apache.calcite.rel.core.AggregateCall;
+import org.apache.calcite.rel.core.Aggregate;
+import org.apache.calcite.rel.type.RelDataType;
+import org.apache.calcite.rel.type.RelDataTypeField;
+import org.apache.calcite.rel.type.RelDataTypeFieldImpl;
+import org.apache.calcite.rel.type.RelRecordType;
+import org.apache.calcite.rex.RexInputRef;
+import org.apache.calcite.rex.RexNode;
+import org.apache.calcite.sql.type.SqlTypeName;
+
+import java.util.List;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Iterator;
+import java.util.LinkedHashMap;
+
+/**
+ * A utility class that contains helper functions used by rules that convert COUNT(*) and
COUNT(col)
+ * aggregates (no group-by) to DirectScan
+ */
+public class CountToDirectScanUtils {
+
+  /**
+   * Checks if aggregate call contains star or non-null expression:
+   * <pre>
+   * count(*)  == >  empty arg  ==>  rowCount
+   * count(Not-null-input) ==> rowCount
+   * </pre>
+   *
+   * @param aggregateCall aggregate call
+   * @param aggregate aggregate relation expression
+   * @return true of aggregate call contains star or non-null expression
+   */
+  public static boolean containsStarOrNotNullInput(AggregateCall aggregateCall, Aggregate
aggregate) {
+    return aggregateCall.getArgList().isEmpty() ||
+        (aggregateCall.getArgList().size() == 1 &&
+            !aggregate.getInput().getRowType().getFieldList().get(aggregateCall.getArgList().get(0)).getType().isNullable());
+  }
+
+  /**
+   * For each aggregate call creates field based on its name with bigint type.
+   * Constructs record type for created fields.
+   *
+   * @param aggregateRel aggregate relation expression
+   * @param fieldNames field names
+   * @return record type
+   */
+  public static RelDataType constructDataType(Aggregate aggregateRel, Collection<String>
fieldNames) {
+    List<RelDataTypeField> fields = new ArrayList<>();
+    Iterator<String> filedNamesIterator = fieldNames.iterator();
 
 Review comment:
   Nit: iterator usage may be replaced with `for-each` loop.

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