vxquery-core/src/main/java/org/apache/vxquery/compiler/rewriter/rules/SetVariableIdContextRule.java

/*
 * 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.vxquery.compiler.rewriter.rules;

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

import org.apache.hyracks.algebricks.common.exceptions.AlgebricksException;
import org.apache.hyracks.algebricks.core.algebra.base.ILogicalOperator;
import org.apache.hyracks.algebricks.core.algebra.base.IOptimizationContext;
import org.apache.hyracks.algebricks.core.algebra.operators.logical.AbstractAssignOperator;
import org.apache.hyracks.algebricks.core.algebra.operators.logical.AbstractLogicalOperator;
import org.apache.hyracks.algebricks.core.algebra.operators.logical.UnnestOperator;
import org.apache.hyracks.algebricks.core.rewriter.base.IAlgebraicRewriteRule;

/**
 * Set the default context for the variable id in the optimization context.
 * 
 * @author prestonc
 */
public class SetVariableIdContextRule implements IAlgebraicRewriteRule {
    @Override
    public boolean rewritePre(Mutable<ILogicalOperator> opRef, IOptimizationContext context)
            throws AlgebricksException {
        if (context.checkIfInDontApplySet(this, opRef.getValue())) {
            return false;
        }
        int variableId = 0;

        // TODO Move the setVarCounter to the compiler after the translator has run.
        AbstractLogicalOperator op = (AbstractLogicalOperator) opRef.getValue();
        switch (op.getOperatorTag()) {
            case ASSIGN:
            case AGGREGATE:
                AbstractAssignOperator assign = (AbstractAssignOperator) op;
                if (assign.getVariables().size() > 0) {
                    variableId = assign.getVariables().get(0).getId();
                }
                break;
            case UNNEST:
                UnnestOperator unnest = (UnnestOperator) op;
                variableId = unnest.getVariable().getId();
                break;
            default:
                return false;
        }

        if (context.getVarCounter() <= variableId) {
            context.setVarCounter(variableId + 1);
        }
        context.addToDontApplySet(this, opRef.getValue());
        return false;
    }

    @Override
    public boolean rewritePost(Mutable<ILogicalOperator> opRef, IOptimizationContext context)
            throws AlgebricksException {
        return false;
    }
}