Github user paul-rogers commented on a diff in the pull request:
https://github.com/apache/drill/pull/729#discussion_r102870259
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/physical/impl/statistics/AvgWidthMergedStatistic.java
---
@@ -0,0 +1,135 @@
+/*
+ * 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
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * 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.physical.impl.statistics;
+
+import org.apache.drill.common.types.TypeProtos;
+import org.apache.drill.exec.expr.holders.NullableFloat8Holder;
+import org.apache.drill.exec.expr.holders.ValueHolder;
+import org.apache.drill.exec.vector.NullableFloat8Vector;
+import org.apache.drill.exec.vector.ValueVector;
+import org.apache.drill.exec.vector.complex.MapVector;
+
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+public class AvgWidthMergedStatistic extends AbstractMergedStatistic {
+
+ private String name;
+ private String inputName;
+ private boolean configureComplete = false;
+ private boolean mergeComplete = false;
+ private Map<String, ValueHolder> sumHolder;
+ MergedStatistic types, nonNullStatCounts, statCounts;
+
+ public AvgWidthMergedStatistic (String name, String inputName) {
+ this.name = name;
+ this.inputName = inputName;
+ this.sumHolder = new HashMap<>();
+ types = nonNullStatCounts = statCounts = null;
+ }
+
+ @Override
+ public String getName() {
+ return name;
+ }
+
+ @Override
+ public String getInput() {
+ return inputName;
+ }
+
+ @Override
+ public void merge(ValueVector input) {
+ // Check the input is a Map Vector
+ assert (input.getField().getType().getMinorType() ==
TypeProtos.MinorType.MAP);
+ MapVector inputMap = (MapVector) input;
+ for (ValueVector vv : inputMap) {
+ String colName = vv.getField().getLastName();
+ NullableFloat8Holder colSumHolder;
+ if (sumHolder.get(colName) != null) {
+ colSumHolder = (NullableFloat8Holder) sumHolder.get(colName);
+ } else {
+ colSumHolder = new NullableFloat8Holder();
+ sumHolder.put(colName, colSumHolder);
+ }
+ Object val = vv.getAccessor().getObject(0);
+ if (val != null) {
+ colSumHolder.value += (double) val;
+ colSumHolder.isSet = 1;
+ }
+ }
+ }
+
+ @Override
+ public Object getStat(String colName) {
+ if (mergeComplete != true) {
+ throw new IllegalStateException(
+ String.format("Statistic `%s` has not completed merging
statistics", name));
+ }
+ NullableFloat8Holder colSumHolder = (NullableFloat8Holder)
sumHolder.get(colName);
+ return (long) (colSumHolder.value/ getRowCount(colName));
--- End diff --
In Drill, different columns generally cannot have different row counts. In
any vector, all columns must have the same number of values. Or, is the
`getRowCount` method really `getNonNullValueCount`: the number of rows for
which the column in question had non-null values?
By discarding the holder, the above reduces to:
```
return Math.round(colSum / rowCount);
```
Also, I'm not really sure what this is doing. The sum seems global, but the
value returned is per column, with only the row count differing between
columns? Perhaps explain that a bit?...
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