Github user gparai commented on a diff in the pull request:
https://github.com/apache/drill/pull/729#discussion_r103617262
--- 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));
+ }
+
+ @Override
+ public void setOutput(ValueVector output) {
+ // Check the input is a Map Vector
+ assert (output.getField().getType().getMinorType() ==
TypeProtos.MinorType.MAP);
+ // Dependencies have been configured correctly
+ assert (configureComplete == true);
+ MapVector outputMap = (MapVector) output;
+
+ for (ValueVector outMapCol : outputMap) {
+ String colName = outMapCol.getField().getLastName();
+ NullableFloat8Holder colSumHolder = (NullableFloat8Holder)
sumHolder.get(colName);
+ NullableFloat8Vector vv = (NullableFloat8Vector) outMapCol;
+ vv.allocateNewSafe();
+ vv.getMutator().setSafe(0, (colSumHolder.value /
getRowCount(colName)));
+ }
+ mergeComplete = true;
+ }
+
+ @Override
+ public void configure(Object configurations) {
+ List<MergedStatistic> statistics = (List<MergedStatistic>)
configurations;
+ for (MergedStatistic statistic : statistics) {
+ if (statistic.getName().equals("type")) {
+ types = statistic;
+ } else if (statistic.getName().equals("statcount")) {
+ statCounts = statistic;
+ } else if (statistic.getName().equals("nonnullstatcount")) {
+ nonNullStatCounts = statistic;
+ }
+ }
+ assert (types != null && statCounts != null && nonNullStatCounts !=
null);
+ configureComplete = true;
+ }
+
+ private long getRowCount(String colName) {
+ int type = (int) types.getStat(colName);
+ // If variable type - then use the nonNullCount. Otherwise, use the
Count,
+ // since even NULL values take up the same space.
+ if (type == TypeProtos.MinorType.VAR16CHAR.getNumber()
+ || type == TypeProtos.MinorType.VARCHAR.getNumber()
+ || type == TypeProtos.MinorType.VARBINARY.getNumber()) {
+ return (long) nonNullStatCounts.getStat(colName);
+ } else {
+ return (long) statCounts.getStat(colName);
--- End diff --
Since the `MapVector` itself does not guarantee any order for the
`ValueVectors` inside, we would have to reconstruct the index every time in
`MergedStatistic.merge()` which would be expensive. For
`MergedStatistic.output()` we only do it once per column. Also, all the
MergedStatistic operations would be done on one RecordBatch, so it should have
minimal performance impact, if any. Keeping the code simple seems to be the
better choice here.
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