Github user JamesRTaylor commented on a diff in the pull request:
https://github.com/apache/phoenix/pull/308#discussion_r204168576
--- Diff:
phoenix-core/src/main/java/org/apache/phoenix/iterate/ClientHashAggregatingResultIterator.java
---
@@ -0,0 +1,189 @@
+/*
+ * 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.compile.StatementContext;
+import org.apache.phoenix.expression.Expression;
+import org.apache.phoenix.expression.aggregator.Aggregator;
+import org.apache.phoenix.expression.aggregator.Aggregators;
+import org.apache.phoenix.memory.MemoryManager.MemoryChunk;
+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.SizedUtil;
+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 int CLIENT_HASH_AGG_MEMORY_CHUNK_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 final MemoryChunk memoryChunk;
+ private HashMap<ImmutableBytesWritable, Aggregator[]> hash;
+ private List<ImmutableBytesWritable> keyList;
+ private Iterator<ImmutableBytesWritable> keyIterator;
+
+ public ClientHashAggregatingResultIterator(StatementContext context,
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;
+ memoryChunk =
context.getConnection().getQueryServices().getMemoryManager().allocate(CLIENT_HASH_AGG_MEMORY_CHUNK_SIZE);
+ }
+
+ @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;
+ memoryChunk.resize(0);
+ 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();
+
+ for (Tuple result = resultIterator.next(); result != null; result
= resultIterator.next()) {
+ ImmutableBytesWritable key = new
ImmutableBytesWritable(UNITIALIZED_KEY_BUFFER);
+ key = getGroupingKey(result, key);
+ Aggregator[] rowAggregators = hash.get(key);
+ if (rowAggregators == null) {
+ long hashSize = SizedUtil.sizeOfMap(hash.size() + 1,
key.getSize(), aggSize);
+ if (hashSize > memoryChunk.getSize() +
CLIENT_HASH_AGG_MEMORY_CHUNK_SIZE) {
+ // This will throw InsufficientMemoryException if
necessary
+ memoryChunk.resize(hashSize +
CLIENT_HASH_AGG_MEMORY_CHUNK_SIZE);
+ }
+
+ // Abort if we exceed memory threshold/2
+ // We use threshold/2 to leave room for the subsequent sort
+ if (thresholdBytes > 0) {
+ if (hashSize > thresholdBytes/2) {
--- End diff --
I don't think we need this since we're tracking memory in a different way
now. This would put a constraint on each client side aggregation (rather than
memory usage as a whole). Do you think that additional constraint is necessary
and if so why? FYI, you can also set an absolute byte amount for memory usage
(but this is mainly used in tests). If you want to keep this, then let's create
a different config parameter in QueryServices and a default in
QueryServiesOptions. The spooling threshold is not a memory constraint. It's
tells Phoenix when to start spooling to disk during a client sort, so it's not
really appropriate to use here.
---
