Github user geraldss commented on a diff in the pull request:
https://github.com/apache/phoenix/pull/308#discussion_r203926206
--- Diff:
phoenix-core/src/main/java/org/apache/phoenix/iterate/ClientHashAggregatingResultIterator.java
---
@@ -0,0 +1,173 @@
+/*
+ * 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.phoenix.iterate;
+
+import static org.apache.phoenix.query.QueryConstants.AGG_TIMESTAMP;
+import static org.apache.phoenix.query.QueryConstants.SINGLE_COLUMN;
+import static org.apache.phoenix.query.QueryConstants.SINGLE_COLUMN_FAMILY;
+
+import java.io.IOException;
+import java.sql.SQLException;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+
+import org.apache.hadoop.hbase.Cell;
+import org.apache.hadoop.hbase.KeyValue;
+import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
+import org.apache.phoenix.expression.Expression;
+import org.apache.phoenix.expression.aggregator.Aggregator;
+import org.apache.phoenix.expression.aggregator.Aggregators;
+import org.apache.phoenix.schema.tuple.MultiKeyValueTuple;
+import org.apache.phoenix.schema.tuple.Tuple;
+import org.apache.phoenix.util.KeyValueUtil;
+import org.apache.phoenix.util.TupleUtil;
+
+/**
+ *
+ * This class implements client-side hash aggregation in memory.
+ * Issue https://issues.apache.org/jira/browse/PHOENIX-4751.
+ *
+ */
+public class ClientHashAggregatingResultIterator
+ implements AggregatingResultIterator {
+
+ private static final int HASH_AGG_INIT_SIZE = 64*1024;
+ private static final byte[] UNITIALIZED_KEY_BUFFER = new byte[0];
+ private final ResultIterator resultIterator;
+ private final Aggregators aggregators;
+ private final List<Expression> groupByExpressions;
+ private final int thresholdBytes;
+ private HashMap<ImmutableBytesWritable, Aggregator[]> hash;
+ private List<ImmutableBytesWritable> keyList;
+ private Iterator<ImmutableBytesWritable> keyIterator;
+
+ public ClientHashAggregatingResultIterator(ResultIterator
resultIterator, Aggregators aggregators, List<Expression> groupByExpressions,
int thresholdBytes) {
+ Objects.requireNonNull(resultIterator);
+ Objects.requireNonNull(aggregators);
+ Objects.requireNonNull(groupByExpressions);
+ this.resultIterator = resultIterator;
+ this.aggregators = aggregators;
+ this.groupByExpressions = groupByExpressions;
+ this.thresholdBytes = thresholdBytes;
+ }
+
+ @Override
+ public Tuple next() throws SQLException {
+ if (keyIterator == null) {
+ hash = populateHash();
+ keyList = sortKeys();
+ keyIterator = keyList.iterator();
+ }
+
+ if (!keyIterator.hasNext()) {
+ return null;
+ }
+
+ ImmutableBytesWritable key = keyIterator.next();
+ Aggregator[] rowAggregators = hash.get(key);
+ byte[] value = aggregators.toBytes(rowAggregators);
+ Tuple tuple = wrapKeyValueAsResult(KeyValueUtil.newKeyValue(key,
SINGLE_COLUMN_FAMILY, SINGLE_COLUMN, AGG_TIMESTAMP, value, 0, value.length));
+ return tuple;
+ }
+
+ @Override
+ public void close() throws SQLException {
+ keyIterator = null;
+ keyList = null;
+ hash = null;
+ resultIterator.close();
+ }
+
+ @Override
+ public Aggregator[] aggregate(Tuple result) {
+ Aggregator[] rowAggregators = aggregators.getAggregators();
+ aggregators.reset(rowAggregators);
+ aggregators.aggregate(rowAggregators, result);
+ return rowAggregators;
+ }
+
+ @Override
+ public void explain(List<String> planSteps) {
+ resultIterator.explain(planSteps);
+ }
+
+ @Override
+ public String toString() {
+ return "ClientHashAggregatingResultIterator [resultIterator="
+ + resultIterator + ", aggregators=" + aggregators + ",
groupByExpressions="
+ + groupByExpressions + "]";
+ }
+
+ // Copied from ClientGroupedAggregatingResultIterator
+ protected ImmutableBytesWritable getGroupingKey(Tuple tuple,
ImmutableBytesWritable ptr) throws SQLException {
+ try {
+ ImmutableBytesWritable key =
TupleUtil.getConcatenatedValue(tuple, groupByExpressions);
+ ptr.set(key.get(), key.getOffset(), key.getLength());
+ return ptr;
+ } catch (IOException e) {
+ throw new SQLException(e);
+ }
+ }
+
+ // Copied from ClientGroupedAggregatingResultIterator
+ protected Tuple wrapKeyValueAsResult(KeyValue keyValue) {
+ return new MultiKeyValueTuple(Collections.<Cell>
singletonList(keyValue));
+ }
+
+ private HashMap<ImmutableBytesWritable, Aggregator[]> populateHash()
throws SQLException {
+ hash = new HashMap<ImmutableBytesWritable,
Aggregator[]>(HASH_AGG_INIT_SIZE, 0.75f);
+
+ final int aggSize = aggregators.getEstimatedByteSize();
+ int hashSize = 0;
--- End diff --
Done.
---
