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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.
*/
package org.apache.hadoop.hive.ql.optimizer.calcite.stats;
import java.util.ArrayList;
import java.util.List;
import java.util.Set;
import org.apache.calcite.plan.RelOptUtil;
import org.apache.calcite.plan.hep.HepRelVertex;
import org.apache.calcite.rel.RelNode;
import org.apache.calcite.rel.RelVisitor;
import org.apache.calcite.rel.core.Filter;
import org.apache.calcite.rel.core.Join;
import org.apache.calcite.rel.core.JoinRelType;
import org.apache.calcite.rel.core.Project;
import org.apache.calcite.rel.core.SemiJoin;
import org.apache.calcite.rel.core.TableScan;
import org.apache.calcite.rel.metadata.ReflectiveRelMetadataProvider;
import org.apache.calcite.rel.metadata.RelMdRowCount;
import org.apache.calcite.rel.metadata.RelMetadataProvider;
import org.apache.calcite.rel.metadata.RelMetadataQuery;
import org.apache.calcite.rex.RexBuilder;
import org.apache.calcite.rex.RexCall;
import org.apache.calcite.rex.RexInputRef;
import org.apache.calcite.rex.RexNode;
import org.apache.calcite.rex.RexUtil;
import org.apache.calcite.sql.fun.SqlStdOperatorTable;
import org.apache.calcite.util.BuiltInMethod;
import org.apache.calcite.util.ImmutableBitSet;
import org.apache.calcite.util.Pair;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.hive.ql.optimizer.calcite.reloperators.HiveTableScan;
public class HiveRelMdRowCount extends RelMdRowCount {
protected static final Log LOG = LogFactory.getLog(HiveRelMdRowCount.class.getName());
public static final RelMetadataProvider SOURCE = ReflectiveRelMetadataProvider
.reflectiveSource(BuiltInMethod.ROW_COUNT.method, new HiveRelMdRowCount());
protected HiveRelMdRowCount() {
super();
}
public Double getRowCount(Join join) {
PKFKRelationInfo pkfk = analyzeJoinForPKFK(join);
if (pkfk != null) {
double selectivity = (pkfk.pkInfo.selectivity * pkfk.ndvScalingFactor);
selectivity = Math.min(1.0, selectivity);
if (LOG.isDebugEnabled()) {
LOG.debug("Identified Primary - Foreign Key relation:");
LOG.debug(RelOptUtil.toString(join));
LOG.debug(pkfk);
}
return pkfk.fkInfo.rowCount * selectivity;
}
return join.getRows();
}
public Double getRowCount(SemiJoin rel) {
PKFKRelationInfo pkfk = analyzeJoinForPKFK(rel);
if (pkfk != null) {
double selectivity = (pkfk.pkInfo.selectivity * pkfk.ndvScalingFactor);
selectivity = Math.min(1.0, selectivity);
if (LOG.isDebugEnabled()) {
LOG.debug("Identified Primary - Foreign Key relation:");
LOG.debug(RelOptUtil.toString(rel));
LOG.debug(pkfk);
}
return pkfk.fkInfo.rowCount * selectivity;
}
return super.getRowCount(rel);
}
static class PKFKRelationInfo {
public final int fkSide;
public final double ndvScalingFactor;
public final FKSideInfo fkInfo;
public final PKSideInfo pkInfo;
public final boolean isPKSideSimple;
PKFKRelationInfo(int fkSide,
FKSideInfo fkInfo,
PKSideInfo pkInfo,
double ndvScalingFactor,
boolean isPKSideSimple) {
this.fkSide = fkSide;
this.fkInfo = fkInfo;
this.pkInfo = pkInfo;
this.ndvScalingFactor = ndvScalingFactor;
this.isPKSideSimple = isPKSideSimple;
}
public String toString() {
return String.format(
"Primary - Foreign Key join:\n\tfkSide = %d\n\tFKInfo:%s\n" +
"\tPKInfo:%s\n\tisPKSideSimple:%s\n\tNDV Scaling Factor:%.2f\n",
fkSide,
fkInfo,
pkInfo,
isPKSideSimple,
ndvScalingFactor);
}
}
static class FKSideInfo {
public final double rowCount;
public final double distinctCount;
public FKSideInfo(double rowCount, double distinctCount) {
this.rowCount = rowCount;
this.distinctCount = distinctCount;
}
public String toString() {
return String.format("FKInfo(rowCount=%.2f,ndv=%.2f)", rowCount, distinctCount);
}
}
static class PKSideInfo extends FKSideInfo {
public final double selectivity;
public PKSideInfo(double rowCount, double distinctCount, double selectivity) {
super(rowCount, distinctCount);
this.selectivity = selectivity;
}
public String toString() {
return String.format("PKInfo(rowCount=%.2f,ndv=%.2f,selectivity=%.2f)", rowCount, distinctCount,selectivity);
}
}
/*
* For T1 join T2 on T1.x = T2.y if we identify 'y' s a key of T2 then we can
* infer the join cardinality as: rowCount(T1) * selectivity(T2) i.e this is
* like a SemiJoin where the T1(Fact side/FK side) is filtered by a factor
* based on the Selectivity of the PK/Dim table side.
*
* 1. If both T1.x and T2.y are keys then use the larger one as the PK side.
* 2. In case of outer Joins: a) The FK side should be the Null Preserving
* side. It doesn't make sense to apply this heuristic in case of Dim loj Fact
* or Fact roj Dim b) The selectivity factor applied on the Fact Table should
* be 1.
*/
public static PKFKRelationInfo analyzeJoinForPKFK(Join joinRel) {
RelNode left = joinRel.getInputs().get(0);
RelNode right = joinRel.getInputs().get(1);
final List initJoinFilters = RelOptUtil.conjunctions(joinRel
.getCondition());
/*
* No joining condition.
*/
if (initJoinFilters.isEmpty()) {
return null;
}
List leftFilters = new ArrayList();
List rightFilters = new ArrayList();
List joinFilters = new ArrayList(initJoinFilters);
// @todo: remove this. 8/28/14 hb
// for now adding because RelOptUtil.classifyFilters has an assertion about
// column counts that is not true for semiJoins.
if (joinRel instanceof SemiJoin) {
return null;
}
RelOptUtil.classifyFilters(joinRel, joinFilters, joinRel.getJoinType(),
false, !joinRel.getJoinType().generatesNullsOnRight(), !joinRel
.getJoinType().generatesNullsOnLeft(), joinFilters, leftFilters,
rightFilters);
Pair joinCols = canHandleJoin(joinRel, leftFilters,
rightFilters, joinFilters);
if (joinCols == null) {
return null;
}
int leftColIdx = joinCols.left;
int rightColIdx = joinCols.right;
RexBuilder rexBuilder = joinRel.getCluster().getRexBuilder();
RexNode leftPred = RexUtil
.composeConjunction(rexBuilder, leftFilters, true);
RexNode rightPred = RexUtil.composeConjunction(rexBuilder, rightFilters,
true);
ImmutableBitSet lBitSet = ImmutableBitSet.of(leftColIdx);
ImmutableBitSet rBitSet = ImmutableBitSet.of(rightColIdx);
/*
* If the form is Dim loj F or Fact roj Dim or Dim semij Fact then return
* null.
*/
boolean leftIsKey = (joinRel.getJoinType() == JoinRelType.INNER || joinRel
.getJoinType() == JoinRelType.RIGHT)
&& !(joinRel instanceof SemiJoin) && isKey(lBitSet, left);
boolean rightIsKey = (joinRel.getJoinType() == JoinRelType.INNER || joinRel
.getJoinType() == JoinRelType.LEFT) && isKey(rBitSet, right);
if (!leftIsKey && !rightIsKey) {
return null;
}
double leftRowCount = RelMetadataQuery.getRowCount(left);
double rightRowCount = RelMetadataQuery.getRowCount(right);
if (leftIsKey && rightIsKey) {
if (rightRowCount < leftRowCount) {
leftIsKey = false;
}
}
int pkSide = leftIsKey ? 0 : rightIsKey ? 1 : -1;
boolean isPKSideSimpleTree = pkSide != -1 ?
IsSimpleTreeOnJoinKey.check(
pkSide == 0 ? left : right,
pkSide == 0 ? leftColIdx : rightColIdx) : false;
double leftNDV = isPKSideSimpleTree ? RelMetadataQuery.getDistinctRowCount(left, lBitSet, leftPred) : -1;
double rightNDV = isPKSideSimpleTree ? RelMetadataQuery.getDistinctRowCount(right, rBitSet, rightPred) : -1;
/*
* If the ndv of the PK - FK side don't match, and the PK side is a filter
* on the Key column then scale the NDV on the FK side.
*
* As described by Peter Boncz: http://databasearchitects.blogspot.com/
* in such cases we can be off by a large margin in the Join cardinality
* estimate. The e.g. he provides is on the join of StoreSales and DateDim
* on the TPCDS dataset. Since the DateDim is populated for 20 years into
* the future, while the StoreSales only has 5 years worth of data, there
* are 40 times fewer distinct dates in StoreSales.
*
* In general it is hard to infer the range for the foreign key on an
* arbitrary expression. For e.g. the NDV for DayofWeek is the same
* irrespective of NDV on the number of unique days, whereas the
* NDV of Quarters has the same ratio as the NDV on the keys.
*
* But for expressions that apply only on columns that have the same NDV
* as the key (implying that they are alternate keys) we can apply the
* ratio. So in the case of StoreSales - DateDim joins for predicate on the
* d_date column we can apply the scaling factor.
*/
double ndvScalingFactor = 1.0;
if ( isPKSideSimpleTree ) {
ndvScalingFactor = pkSide == 0 ? leftNDV/rightNDV : rightNDV / leftNDV;
}
if (pkSide == 0) {
FKSideInfo fkInfo = new FKSideInfo(rightRowCount,
rightNDV);
double pkSelectivity = pkSelectivity(joinRel, true, left, leftRowCount);
PKSideInfo pkInfo = new PKSideInfo(leftRowCount,
leftNDV,
joinRel.getJoinType().generatesNullsOnRight() ? 1.0 :
pkSelectivity);
return new PKFKRelationInfo(1, fkInfo, pkInfo, ndvScalingFactor, isPKSideSimpleTree);
}
if (pkSide == 1) {
FKSideInfo fkInfo = new FKSideInfo(leftRowCount,
leftNDV);
double pkSelectivity = pkSelectivity(joinRel, false, right, rightRowCount);
PKSideInfo pkInfo = new PKSideInfo(rightRowCount,
rightNDV,
joinRel.getJoinType().generatesNullsOnLeft() ? 1.0 :
pkSelectivity);
return new PKFKRelationInfo(1, fkInfo, pkInfo, ndvScalingFactor, isPKSideSimpleTree);
}
return null;
}
private static double pkSelectivity(Join joinRel, boolean leftChild,
RelNode child,
double childRowCount) {
if ((leftChild && joinRel.getJoinType().generatesNullsOnRight()) ||
(!leftChild && joinRel.getJoinType().generatesNullsOnLeft())) {
return 1.0;
} else {
HiveTableScan tScan = HiveRelMdUniqueKeys.getTableScan(child, true);
if (tScan != null) {
double tRowCount = RelMetadataQuery.getRowCount(tScan);
return childRowCount / tRowCount;
} else {
return 1.0;
}
}
}
private static boolean isKey(ImmutableBitSet c, RelNode rel) {
boolean isKey = false;
Set keys = RelMetadataQuery.getUniqueKeys(rel);
if (keys != null) {
for (ImmutableBitSet key : keys) {
if (key.equals(c)) {
isKey = true;
break;
}
}
}
return isKey;
}
/*
* 1. Join condition must be an Equality Predicate.
* 2. both sides must reference 1 column.
* 3. If needed flip the columns.
*/
private static Pair canHandleJoin(Join joinRel,
List leftFilters, List rightFilters,
List joinFilters) {
/*
* If after classifying filters there is more than 1 joining predicate, we
* don't handle this. Return null.
*/
if (joinFilters.size() != 1) {
return null;
}
RexNode joinCond = joinFilters.get(0);
int leftColIdx;
int rightColIdx;
if (!(joinCond instanceof RexCall)) {
return null;
}
if (((RexCall) joinCond).getOperator() != SqlStdOperatorTable.EQUALS) {
return null;
}
ImmutableBitSet leftCols = RelOptUtil.InputFinder.bits(((RexCall) joinCond).getOperands().get(0));
ImmutableBitSet rightCols = RelOptUtil.InputFinder.bits(((RexCall) joinCond).getOperands().get(1));
if (leftCols.cardinality() != 1 || rightCols.cardinality() != 1 ) {
return null;
}
int nFieldsLeft = joinRel.getLeft().getRowType().getFieldList().size();
int nFieldsRight = joinRel.getRight().getRowType().getFieldList().size();
int nSysFields = joinRel.getSystemFieldList().size();
ImmutableBitSet rightFieldsBitSet = ImmutableBitSet.range(nSysFields + nFieldsLeft,
nSysFields + nFieldsLeft + nFieldsRight);
/*
* flip column references if join condition specified in reverse order to
* join sources.
*/
if (rightFieldsBitSet.contains(leftCols)) {
ImmutableBitSet t = leftCols;
leftCols = rightCols;
rightCols = t;
}
leftColIdx = leftCols.nextSetBit(0) - nSysFields;
rightColIdx = rightCols.nextSetBit(0) - (nSysFields + nFieldsLeft);
return new Pair(leftColIdx, rightColIdx);
}
private static class IsSimpleTreeOnJoinKey extends RelVisitor {
int joinKey;
boolean simpleTree;
static boolean check(RelNode r, int joinKey) {
IsSimpleTreeOnJoinKey v = new IsSimpleTreeOnJoinKey(joinKey);
v.go(r);
return v.simpleTree;
}
IsSimpleTreeOnJoinKey(int joinKey) {
super();
this.joinKey = joinKey;
simpleTree = true;
}
@Override
public void visit(RelNode node, int ordinal, RelNode parent) {
if (node instanceof HepRelVertex) {
node = ((HepRelVertex) node).getCurrentRel();
}
if (node instanceof TableScan) {
simpleTree = true;
} else if (node instanceof Project) {
simpleTree = isSimple((Project) node);
} else if (node instanceof Filter) {
simpleTree = isSimple((Filter) node);
} else {
simpleTree = false;
}
if (simpleTree) {
super.visit(node, ordinal, parent);
}
}
private boolean isSimple(Project project) {
RexNode r = project.getProjects().get(joinKey);
if (r instanceof RexInputRef) {
joinKey = ((RexInputRef) r).getIndex();
return true;
}
return false;
}
private boolean isSimple(Filter filter) {
ImmutableBitSet condBits = RelOptUtil.InputFinder.bits(filter.getCondition());
return isKey(condBits, filter);
}
}
}
