/*
* 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.vxquery.compiler.rewriter.rules.util.ExpressionToolbox;
import org.apache.vxquery.functions.Function;
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.expressions.AbstractFunctionCallExpression;
import edu.uci.ics.hyracks.algebricks.core.algebra.expressions.ScalarFunctionCallExpression;
import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.AbstractLogicalOperator;
import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.UnnestOperator;
/**
* The rule searches for an unnest operator (1) immediately following an unnest
* operator (2). XQuery unnest operator (1) must have a scalar implementation
* of the unnest function. If so the two unnest expressions can be merged
* together.
*
* <pre>
* Before
*
* plan__parent
* UNNEST( $v2 : uf2( $v1 ) )
* UNNEST( $v1 : uf1( $v0 ) )
* plan__child
*
* Where $v1 is not used in plan__parent.
*
* After
*
* plan__parent
* UNNEST( $v2 : uf2( sf1( $v0 ) ) )
* plan__child
*
* uf1 becomes sf1 since it changes from unnesting to scalar expression.
* </pre>
*
* @author prestonc
*/
public class ConsolidateUnnestsRule extends AbstractUsedVariablesProcessingRule {
protected boolean processOperator(Mutable<ILogicalOperator> opRef, IOptimizationContext context)
throws AlgebricksException {
AbstractLogicalOperator op = (AbstractLogicalOperator) opRef.getValue();
if (op.getOperatorTag() != LogicalOperatorTag.UNNEST) {
return false;
}
UnnestOperator unnest1 = (UnnestOperator) op;
AbstractLogicalOperator op2 = (AbstractLogicalOperator) unnest1.getInputs().get(0).getValue();
if (op2.getOperatorTag() != LogicalOperatorTag.UNNEST) {
return false;
}
UnnestOperator unnest2 = (UnnestOperator) op2;
if (!usedVariables.contains(unnest2.getVariable())) {
// Check to see if the unnest2 expression has a scalar implementation.
ILogicalExpression logicalExpression2 = (ILogicalExpression) unnest2.getExpressionRef().getValue();
if (logicalExpression2.getExpressionTag() != LogicalExpressionTag.FUNCTION_CALL) {
return false;
}
AbstractFunctionCallExpression functionCall2 = (AbstractFunctionCallExpression) logicalExpression2;
Function functionInfo2 = (Function) functionCall2.getFunctionInfo();
if (!functionInfo2.hasScalarEvaluatorFactory()) {
return false;
}
// Find unnest2 variable in unnest1
Mutable<ILogicalExpression> unnest1Arg = ExpressionToolbox.findVariableExpression(
unnest1.getExpressionRef(), unnest2.getVariable());
if (unnest1Arg == null) {
return false;
}
// Replace unnest2 expression in unnest1
ScalarFunctionCallExpression child = new ScalarFunctionCallExpression(functionInfo2,
functionCall2.getArguments());
unnest1Arg.setValue(child);
// Move input for unnest2 into unnest1
unnest1.getInputs().clear();
unnest1.getInputs().addAll(unnest2.getInputs());
return true;
}
return false;
}
}