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AggregationStatsRule.java
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AggregationStatsRule.java
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/*
* Licensed 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 io.prestosql.cost;
import io.prestosql.Session;
import io.prestosql.matching.Pattern;
import io.prestosql.sql.planner.Symbol;
import io.prestosql.sql.planner.TypeProvider;
import io.prestosql.sql.planner.iterative.Lookup;
import io.prestosql.sql.planner.plan.AggregationNode;
import io.prestosql.sql.planner.plan.AggregationNode.Aggregation;
import java.util.Collection;
import java.util.Map;
import java.util.Optional;
import static io.prestosql.sql.planner.plan.AggregationNode.Step.SINGLE;
import static io.prestosql.sql.planner.plan.Patterns.aggregation;
import static java.lang.Math.min;
import static java.util.Objects.requireNonNull;
public class AggregationStatsRule
extends SimpleStatsRule<AggregationNode>
{
private static final Pattern<AggregationNode> PATTERN = aggregation();
public AggregationStatsRule(StatsNormalizer normalizer)
{
super(normalizer);
}
@Override
public Pattern<AggregationNode> getPattern()
{
return PATTERN;
}
@Override
protected Optional<PlanNodeStatsEstimate> doCalculate(AggregationNode node, StatsProvider statsProvider, Lookup lookup, Session session, TypeProvider types)
{
if (node.getGroupingSetCount() != 1) {
return Optional.empty();
}
if (node.getStep() != SINGLE) {
return Optional.empty();
}
return Optional.of(groupBy(
statsProvider.getStats(node.getSource()),
node.getGroupingKeys(),
node.getAggregations()));
}
public static PlanNodeStatsEstimate groupBy(PlanNodeStatsEstimate sourceStats, Collection<Symbol> groupBySymbols, Map<Symbol, Aggregation> aggregations)
{
PlanNodeStatsEstimate.Builder result = PlanNodeStatsEstimate.builder();
for (Symbol groupBySymbol : groupBySymbols) {
SymbolStatsEstimate symbolStatistics = sourceStats.getSymbolStatistics(groupBySymbol);
result.addSymbolStatistics(groupBySymbol, symbolStatistics.mapNullsFraction(nullsFraction -> {
if (nullsFraction == 0.0) {
return 0.0;
}
return 1.0 / (symbolStatistics.getDistinctValuesCount() + 1);
}));
}
double rowsCount = 1;
for (Symbol groupBySymbol : groupBySymbols) {
SymbolStatsEstimate symbolStatistics = sourceStats.getSymbolStatistics(groupBySymbol);
int nullRow = (symbolStatistics.getNullsFraction() == 0.0) ? 0 : 1;
rowsCount *= symbolStatistics.getDistinctValuesCount() + nullRow;
}
result.setOutputRowCount(min(rowsCount, sourceStats.getOutputRowCount()));
for (Map.Entry<Symbol, Aggregation> aggregationEntry : aggregations.entrySet()) {
result.addSymbolStatistics(aggregationEntry.getKey(), estimateAggregationStats(aggregationEntry.getValue(), sourceStats));
}
return result.build();
}
private static SymbolStatsEstimate estimateAggregationStats(Aggregation aggregation, PlanNodeStatsEstimate sourceStats)
{
requireNonNull(aggregation, "aggregation is null");
requireNonNull(sourceStats, "sourceStats is null");
// TODO implement simple aggregations like: min, max, count, sum
return SymbolStatsEstimate.unknown();
}
}