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* 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.
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package org.apache.hadoop.hive.ql.optimizer.optiq.stats;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.Set;
import net.hydromatic.optiq.BuiltinMethod;
import org.apache.hadoop.hive.ql.optimizer.optiq.HiveOptiqUtil.JoinLeafPredicateInfo;
import org.apache.hadoop.hive.ql.optimizer.optiq.HiveOptiqUtil.JoinPredicateInfo;
import org.apache.hadoop.hive.ql.optimizer.optiq.reloperators.HiveJoinRel;
import org.apache.hadoop.hive.ql.optimizer.optiq.reloperators.HiveTableScanRel;
import org.eigenbase.rel.JoinRelType;
import org.eigenbase.rel.metadata.ReflectiveRelMetadataProvider;
import org.eigenbase.rel.metadata.RelMdSelectivity;
import org.eigenbase.rel.metadata.RelMdUtil;
import org.eigenbase.rel.metadata.RelMetadataProvider;
import org.eigenbase.rel.metadata.RelMetadataQuery;
import org.eigenbase.rex.RexNode;
import org.eigenbase.rex.RexUtil;
import org.eigenbase.util.Pair;
import com.google.common.collect.ImmutableMap;
public class HiveRelMdSelectivity extends RelMdSelectivity {
public static final RelMetadataProvider SOURCE = ReflectiveRelMetadataProvider.reflectiveSource(
BuiltinMethod.SELECTIVITY.method,
new HiveRelMdSelectivity());
protected HiveRelMdSelectivity() {
super();
}
public Double getSelectivity(HiveTableScanRel t, RexNode predicate) {
if (predicate != null) {
FilterSelectivityEstimator filterSelEstmator = new FilterSelectivityEstimator(t);
return filterSelEstmator.estimateSelectivity(predicate);
}
return 1.0;
}
public Double getSelectivity(HiveJoinRel j, RexNode predicate) {
if (j.getJoinType().equals(JoinRelType.INNER)) {
return computeInnerJoinSelectivity(j, predicate);
}
return 1.0;
}
private Double computeInnerJoinSelectivity(HiveJoinRel j, RexNode predicate) {
double ndvCrossProduct = 1;
Pair<Boolean, RexNode> predInfo =
getCombinedPredicateForJoin(j, predicate);
if (!predInfo.getKey()) {
return
new FilterSelectivityEstimator(j).
estimateSelectivity(predInfo.getValue());
}
RexNode combinedPredicate = predInfo.getValue();
JoinPredicateInfo jpi = JoinPredicateInfo.constructJoinPredicateInfo(j,
combinedPredicate);
ImmutableMap.Builder<Integer, Double> colStatMapBuilder = ImmutableMap
.builder();
ImmutableMap<Integer, Double> colStatMap;
int rightOffSet = j.getLeft().getRowType().getFieldCount();
// 1. Update Col Stats Map with col stats for columns from left side of
// Join which are part of join keys
for (Integer ljk : jpi.getProjsFromLeftPartOfJoinKeysInChildSchema()) {
colStatMapBuilder.put(ljk,
HiveRelMdDistinctRowCount.getDistinctRowCount(j.getLeft(), ljk));
}
// 2. Update Col Stats Map with col stats for columns from right side of
// Join which are part of join keys
for (Integer rjk : jpi.getProjsFromRightPartOfJoinKeysInChildSchema()) {
colStatMapBuilder.put(rjk + rightOffSet,
HiveRelMdDistinctRowCount.getDistinctRowCount(j.getRight(), rjk));
}
colStatMap = colStatMapBuilder.build();
// 3. Walk through the Join Condition Building NDV for selectivity
// NDV of the join can not exceed the cardinality of cross join.
List<JoinLeafPredicateInfo> peLst = jpi.getEquiJoinPredicateElements();
int noOfPE = peLst.size();
if (noOfPE > 0) {
ndvCrossProduct = exponentialBackoff(peLst, colStatMap);
if (j.isLeftSemiJoin())
ndvCrossProduct = Math.min(RelMetadataQuery.getRowCount(j.getLeft()),
ndvCrossProduct);
else
ndvCrossProduct = Math.min(RelMetadataQuery.getRowCount(j.getLeft())
* RelMetadataQuery.getRowCount(j.getRight()), ndvCrossProduct);
}
// 4. Join Selectivity = 1/NDV
return (1 / ndvCrossProduct);
}
// 3.2 if conjunctive predicate elements are more than one, then walk
// through them one by one. Compute cross product of NDV. Cross product is
// computed by multiplying the largest NDV of all of the conjunctive
// predicate
// elements with degraded NDV of rest of the conjunctive predicate
// elements. NDV is
// degraded using log function.Finally the ndvCrossProduct is fenced at
// the join
// cross product to ensure that NDV can not exceed worst case join
// cardinality.<br>
// NDV of a conjunctive predicate element is the max NDV of all arguments
// to lhs, rhs expressions.
// NDV(JoinCondition) = min (left cardinality * right cardinality,
// ndvCrossProduct(JoinCondition))
// ndvCrossProduct(JoinCondition) = ndv(pex)*log(ndv(pe1))*log(ndv(pe2))
// where pex is the predicate element of join condition with max ndv.
// ndv(pe) = max(NDV(left.Expr), NDV(right.Expr))
// NDV(expr) = max(NDV( expr args))
protected double logSmoothing(List<JoinLeafPredicateInfo> peLst, ImmutableMap<Integer, Double> colStatMap) {
int noOfPE = peLst.size();
double ndvCrossProduct = getMaxNDVForJoinSelectivity(peLst.get(0), colStatMap);
if (noOfPE > 1) {
double maxNDVSoFar = ndvCrossProduct;
double ndvToBeSmoothed;
double tmpNDV;
for (int i = 1; i < noOfPE; i++) {
tmpNDV = getMaxNDVForJoinSelectivity(peLst.get(i), colStatMap);
if (tmpNDV > maxNDVSoFar) {
ndvToBeSmoothed = maxNDVSoFar;
maxNDVSoFar = tmpNDV;
ndvCrossProduct = (ndvCrossProduct / ndvToBeSmoothed) * tmpNDV;
} else {
ndvToBeSmoothed = tmpNDV;
}
// TODO: revisit the fence
if (ndvToBeSmoothed > 3)
ndvCrossProduct *= Math.log(ndvToBeSmoothed);
else
ndvCrossProduct *= ndvToBeSmoothed;
}
}
return ndvCrossProduct;
}
/*
* a) Order predciates based on ndv in reverse order. b) ndvCrossProduct =
* ndv(pe0) * ndv(pe1) ^(1/2) * ndv(pe2) ^(1/4) * ndv(pe3) ^(1/8) ...
*/
protected double exponentialBackoff(List<JoinLeafPredicateInfo> peLst,
ImmutableMap<Integer, Double> colStatMap) {
int noOfPE = peLst.size();
List<Double> ndvs = new ArrayList<Double>(noOfPE);
for (int i = 0; i < noOfPE; i++) {
ndvs.add(getMaxNDVForJoinSelectivity(peLst.get(i), colStatMap));
}
Collections.sort(ndvs);
Collections.reverse(ndvs);
double ndvCrossProduct = 1.0;
for (int i = 0; i < ndvs.size(); i++) {
double n = Math.pow(ndvs.get(i), Math.pow(1 / 2.0, i));
ndvCrossProduct *= n;
}
return ndvCrossProduct;
}
/**
*
* @param j
* @param additionalPredicate
* @return if predicate is the join condition return (true, joinCond)
* else return (false, minusPred)
*/
private Pair<Boolean,RexNode> getCombinedPredicateForJoin(HiveJoinRel j, RexNode additionalPredicate) {
RexNode minusPred = RelMdUtil.minusPreds(j.getCluster().getRexBuilder(), additionalPredicate,
j.getCondition());
if (minusPred != null) {
List<RexNode> minusList = new ArrayList<RexNode>();
minusList.add(j.getCondition());
minusList.add(minusPred);
return new Pair<Boolean,RexNode>(false, minusPred);
}
return new Pair<Boolean,RexNode>(true,j.getCondition());
}
/**
* Compute Max NDV to determine Join Selectivity.
*
* @param jlpi
* @param colStatMap
* Immutable Map of Projection Index (in Join Schema) to Column Stat
* @param rightProjOffSet
* @return
*/
private static Double getMaxNDVForJoinSelectivity(JoinLeafPredicateInfo jlpi,
ImmutableMap<Integer, Double> colStatMap) {
Double maxNDVSoFar = 1.0;
maxNDVSoFar = getMaxNDVFromProjections(colStatMap,
jlpi.getProjsFromLeftPartOfJoinKeysInJoinSchema(), maxNDVSoFar);
maxNDVSoFar = getMaxNDVFromProjections(colStatMap,
jlpi.getProjsFromRightPartOfJoinKeysInJoinSchema(), maxNDVSoFar);
return maxNDVSoFar;
}
private static Double getMaxNDVFromProjections(Map<Integer, Double> colStatMap,
Set<Integer> projectionSet, Double defaultMaxNDV) {
Double colNDV = null;
Double maxNDVSoFar = defaultMaxNDV;
for (Integer projIndx : projectionSet) {
colNDV = colStatMap.get(projIndx);
if (colNDV > maxNDVSoFar)
maxNDVSoFar = colNDV;
}
return maxNDVSoFar;
}
}