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From JamesRTaylor <...@git.apache.org>
Subject [GitHub] phoenix pull request #308: Client-side hash aggregation
Date Thu, 19 Jul 2018 21:47:32 GMT
Github user JamesRTaylor commented on a diff in the pull request:

    https://github.com/apache/phoenix/pull/308#discussion_r203868079
  
    --- 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 --
    
    Instead of just tracking memory and here independently of other queries also running in
this JVM, use our memory manager. This will also automatically track per tenant memory (which
may have lower constraints than the overall allowed memory). Assuming you pass through StatementContext
in the constructor, you can do something like this:
    
        MemoryChunk memoryChunk = context.getConnection().getQueryServices().getMemoryManager()
         .allocate(CLIENT_HASH_AGG_MEMORY_CHUNK_SIZE);


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