| /* |
| * Copyright 2009-2012 by The Regents of the University of California |
| * 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 from |
| * |
| * 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 edu.uci.ics.hyracks.algebricks.rewriter.rules; |
| |
| import java.util.ArrayList; |
| import java.util.Iterator; |
| import java.util.List; |
| import java.util.Set; |
| |
| import org.apache.commons.lang3.mutable.Mutable; |
| import org.apache.commons.lang3.mutable.MutableObject; |
| |
| import edu.uci.ics.hyracks.algebricks.common.exceptions.AlgebricksException; |
| import edu.uci.ics.hyracks.algebricks.core.algebra.base.ILogicalExpression; |
| import edu.uci.ics.hyracks.algebricks.core.algebra.base.ILogicalOperator; |
| import edu.uci.ics.hyracks.algebricks.core.algebra.base.IOptimizationContext; |
| import edu.uci.ics.hyracks.algebricks.core.algebra.base.LogicalExpressionTag; |
| import edu.uci.ics.hyracks.algebricks.core.algebra.base.LogicalOperatorTag; |
| import edu.uci.ics.hyracks.algebricks.core.algebra.base.LogicalVariable; |
| import edu.uci.ics.hyracks.algebricks.core.algebra.expressions.AbstractFunctionCallExpression; |
| import edu.uci.ics.hyracks.algebricks.core.algebra.expressions.AbstractLogicalExpression; |
| import edu.uci.ics.hyracks.algebricks.core.algebra.expressions.VariableReferenceExpression; |
| import edu.uci.ics.hyracks.algebricks.core.algebra.functions.FunctionIdentifier; |
| import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.AbstractBinaryJoinOperator; |
| import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.AbstractLogicalOperator; |
| import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.AssignOperator; |
| import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.visitors.VariableUtilities; |
| import edu.uci.ics.hyracks.algebricks.core.rewriter.base.IAlgebraicRewriteRule; |
| |
| /** |
| * Pushes function-call expressions below a join if possible. |
| * Assigns the result of such function-calls expressions to new variables, and replaces the original |
| * expression with a corresponding variable reference expression. |
| * This rule can help reduce the cost of computing expensive functions by pushing them below |
| * a join (which may blow up the cardinality). |
| * Also, this rule may help to enable other rules such as common subexpression elimination, again to reduce |
| * the number of calls to expensive functions. |
| * |
| * Example: (we are pushing pushMeFunc) |
| * |
| * Before plan: |
| * assign [$$10] <- [funcA(funcB(pushMeFunc($$3, $$4)))] |
| * join (some condition) |
| * join_branch_0 where $$3 and $$4 are not live |
| * ... |
| * join_branch_1 where $$3 and $$4 are live |
| * ... |
| * |
| * After plan: |
| * assign [$$10] <- [funcA(funcB($$11))] |
| * join (some condition) |
| * join_branch_0 where $$3 and $$4 are not live |
| * ... |
| * join_branch_1 where $$3 and $$4 are live |
| * assign[$$11] <- [pushMeFunc($$3, $$4)] |
| * ... |
| */ |
| public class PushFunctionsBelowJoin implements IAlgebraicRewriteRule { |
| |
| private final Set<FunctionIdentifier> toPushFuncIdents; |
| private final List<Mutable<ILogicalExpression>> funcExprs = new ArrayList<Mutable<ILogicalExpression>>(); |
| private final List<LogicalVariable> usedVars = new ArrayList<LogicalVariable>(); |
| private final List<LogicalVariable> liveVars = new ArrayList<LogicalVariable>(); |
| |
| public PushFunctionsBelowJoin(Set<FunctionIdentifier> toPushFuncIdents) { |
| this.toPushFuncIdents = toPushFuncIdents; |
| } |
| |
| @Override |
| public boolean rewritePre(Mutable<ILogicalOperator> opRef, IOptimizationContext context) throws AlgebricksException { |
| return false; |
| } |
| |
| @Override |
| public boolean rewritePost(Mutable<ILogicalOperator> opRef, IOptimizationContext context) |
| throws AlgebricksException { |
| AbstractLogicalOperator op = (AbstractLogicalOperator) opRef.getValue(); |
| if (op.getOperatorTag() != LogicalOperatorTag.ASSIGN) { |
| return false; |
| } |
| AssignOperator assignOp = (AssignOperator) op; |
| |
| // Find a join operator below this assign. |
| Mutable<ILogicalOperator> joinOpRef = findJoinOp(assignOp.getInputs().get(0)); |
| if (joinOpRef == null) { |
| return false; |
| } |
| AbstractBinaryJoinOperator joinOp = (AbstractBinaryJoinOperator) joinOpRef.getValue(); |
| |
| // Check if the assign uses a function that we wish to push below the join if possible. |
| funcExprs.clear(); |
| gatherFunctionCalls(assignOp, funcExprs); |
| if (funcExprs.isEmpty()) { |
| return false; |
| } |
| |
| // Try to push the functions down the input branches of the join. |
| boolean modified = false; |
| if (pushDownFunctions(joinOp, 0, funcExprs, context)) { |
| modified = true; |
| } |
| if (pushDownFunctions(joinOp, 1, funcExprs, context)) { |
| modified = true; |
| } |
| if (modified) { |
| context.computeAndSetTypeEnvironmentForOperator(joinOp); |
| } |
| return modified; |
| } |
| |
| private Mutable<ILogicalOperator> findJoinOp(Mutable<ILogicalOperator> opRef) { |
| AbstractLogicalOperator op = (AbstractLogicalOperator) opRef.getValue(); |
| switch (op.getOperatorTag()) { |
| case INNERJOIN: |
| case LEFTOUTERJOIN: { |
| return opRef; |
| } |
| // Bail on these operators. |
| case GROUP: |
| case AGGREGATE: |
| case DISTINCT: |
| case UNNEST_MAP: { |
| return null; |
| } |
| // Traverse children. |
| default: { |
| for (Mutable<ILogicalOperator> childOpRef : op.getInputs()) { |
| return findJoinOp(childOpRef); |
| } |
| } |
| } |
| return null; |
| } |
| |
| private void gatherFunctionCalls(AssignOperator assignOp, List<Mutable<ILogicalExpression>> funcExprs) { |
| for (Mutable<ILogicalExpression> exprRef : assignOp.getExpressions()) { |
| gatherFunctionCalls(exprRef, funcExprs); |
| } |
| } |
| |
| private void gatherFunctionCalls(Mutable<ILogicalExpression> exprRef, List<Mutable<ILogicalExpression>> funcExprs) { |
| AbstractLogicalExpression expr = (AbstractLogicalExpression) exprRef.getValue(); |
| if (expr.getExpressionTag() != LogicalExpressionTag.FUNCTION_CALL) { |
| return; |
| } |
| // Check whether the function is a function we want to push. |
| AbstractFunctionCallExpression funcExpr = (AbstractFunctionCallExpression) expr; |
| if (toPushFuncIdents.contains(funcExpr.getFunctionIdentifier())) { |
| funcExprs.add(exprRef); |
| } |
| // Traverse arguments. |
| for (Mutable<ILogicalExpression> funcArg : funcExpr.getArguments()) { |
| gatherFunctionCalls(funcArg, funcExprs); |
| } |
| } |
| |
| private boolean pushDownFunctions(AbstractBinaryJoinOperator joinOp, int inputIndex, |
| List<Mutable<ILogicalExpression>> funcExprs, IOptimizationContext context) throws AlgebricksException { |
| ILogicalOperator joinInputOp = joinOp.getInputs().get(inputIndex).getValue(); |
| liveVars.clear(); |
| VariableUtilities.getLiveVariables(joinInputOp, liveVars); |
| Iterator<Mutable<ILogicalExpression>> funcIter = funcExprs.iterator(); |
| List<LogicalVariable> assignVars = null; |
| List<Mutable<ILogicalExpression>> assignExprs = null; |
| while (funcIter.hasNext()) { |
| Mutable<ILogicalExpression> funcExprRef = funcIter.next(); |
| ILogicalExpression funcExpr = funcExprRef.getValue(); |
| usedVars.clear(); |
| funcExpr.getUsedVariables(usedVars); |
| // Check if we can push the function down this branch. |
| if (liveVars.containsAll(usedVars)) { |
| if (assignVars == null) { |
| assignVars = new ArrayList<LogicalVariable>(); |
| assignExprs = new ArrayList<Mutable<ILogicalExpression>>(); |
| } |
| // Replace the original expression with a variable reference expression. |
| LogicalVariable replacementVar = context.newVar(); |
| assignVars.add(replacementVar); |
| assignExprs.add(new MutableObject<ILogicalExpression>(funcExpr)); |
| funcExprRef.setValue(new VariableReferenceExpression(replacementVar)); |
| funcIter.remove(); |
| } |
| } |
| // Create new assign operator below the join if any functions can be pushed. |
| if (assignVars != null) { |
| AssignOperator newAssign = new AssignOperator(assignVars, assignExprs); |
| newAssign.getInputs().add(new MutableObject<ILogicalOperator>(joinInputOp)); |
| newAssign.setExecutionMode(joinOp.getExecutionMode()); |
| joinOp.getInputs().get(inputIndex).setValue(newAssign); |
| context.computeAndSetTypeEnvironmentForOperator(newAssign); |
| return true; |
| } |
| return false; |
| } |
| } |