asterix-algebra/src/main/java/edu/uci/ics/asterix/optimizer/rules/PullPositionalVariableFromUnnestRule.java

package edu.uci.ics.asterix.optimizer.rules;

import java.util.ArrayList;

import org.apache.commons.lang3.mutable.Mutable;
import org.apache.commons.lang3.mutable.MutableObject;

import edu.uci.ics.asterix.aql.util.FunctionUtils;
import edu.uci.ics.asterix.om.functions.AsterixBuiltinFunctions;
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.LogicalOperatorTag;
import edu.uci.ics.hyracks.algebricks.core.algebra.base.LogicalVariable;
import edu.uci.ics.hyracks.algebricks.core.algebra.expressions.StatefulFunctionCallExpression;
import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.AbstractLogicalOperator;
import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.RunningAggregateOperator;
import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.UnnestOperator;
import edu.uci.ics.hyracks.algebricks.core.algebra.operators.physical.RunningAggregatePOperator;
import edu.uci.ics.hyracks.algebricks.core.algebra.properties.UnpartitionedPropertyComputer;
import edu.uci.ics.hyracks.algebricks.core.api.exceptions.AlgebricksException;
import edu.uci.ics.hyracks.algebricks.core.rewriter.base.IAlgebraicRewriteRule;

public class PullPositionalVariableFromUnnestRule implements IAlgebraicRewriteRule {

    @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.UNNEST) {
            return false;
        }
        UnnestOperator unnest = (UnnestOperator) op;
        LogicalVariable p = unnest.getPositionalVariable();
        if (p == null) {
            return false;
        }
        ArrayList<LogicalVariable> rOpVars = new ArrayList<LogicalVariable>();
        rOpVars.add(p);
        ArrayList<Mutable<ILogicalExpression>> rOpExprList = new ArrayList<Mutable<ILogicalExpression>>();
        StatefulFunctionCallExpression fce = new StatefulFunctionCallExpression(
                FunctionUtils.getFunctionInfo(AsterixBuiltinFunctions.TID), UnpartitionedPropertyComputer.INSTANCE);
        rOpExprList.add(new MutableObject<ILogicalExpression>(fce));
        RunningAggregateOperator rOp = new RunningAggregateOperator(rOpVars, rOpExprList);
        rOp.setExecutionMode(unnest.getExecutionMode());
        RunningAggregatePOperator rPop = new RunningAggregatePOperator();
        rOp.setPhysicalOperator(rPop);
        rOp.getInputs().add(new MutableObject<ILogicalOperator>(unnest));
        opRef.setValue(rOp);
        unnest.setPositionalVariable(null);
        context.computeAndSetTypeEnvironmentForOperator(rOp);
        context.computeAndSetTypeEnvironmentForOperator(unnest);
        return true;
    }
}