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/*******************************************************************************
* Copyright (c) 2004-2010 Gabor Bergmann and Daniel Varro
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v. 2.0 which is available at
* http://www.eclipse.org/legal/epl-v20.html.
*
* SPDX-License-Identifier: EPL-2.0
*******************************************************************************/
package tools.refinery.viatra.runtime.matchers.planning.helpers;
import java.util.Collection;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import tools.refinery.viatra.runtime.matchers.ViatraQueryRuntimeException;
import tools.refinery.viatra.runtime.matchers.context.IQueryMetaContext;
import tools.refinery.viatra.runtime.matchers.planning.QueryProcessingException;
import tools.refinery.viatra.runtime.matchers.planning.SubPlan;
import tools.refinery.viatra.runtime.matchers.planning.SubPlanFactory;
import tools.refinery.viatra.runtime.matchers.planning.operations.PProject;
import tools.refinery.viatra.runtime.matchers.psystem.PBody;
import tools.refinery.viatra.runtime.matchers.psystem.PConstraint;
import tools.refinery.viatra.runtime.matchers.psystem.PVariable;
import tools.refinery.viatra.runtime.matchers.psystem.analysis.QueryAnalyzer;
import tools.refinery.viatra.runtime.matchers.psystem.basicdeferred.ExportedParameter;
/**
* @author Gabor Bergmann
*
*/
public class BuildHelper {
private BuildHelper() {
// Hiding constructor for utility class
}
// public static SubPlan naturalJoin(IOperationCompiler buildable,
// SubPlan primaryPlan, SubPlan secondaryPlan) {
// JoinHelper joinHelper = new JoinHelper(primaryPlan, secondaryPlan);
// return buildable.buildBetaNode(primaryPlan, secondaryPlan, joinHelper.getPrimaryMask(),
// joinHelper.getSecondaryMask(), joinHelper.getComplementerMask(), false);
// }
/**
* Reduces the number of tuples by trimming (existentially quantifying) the set of variables that <ul>
* <li> are visible in the subplan,
* <li> are not exported parameters,
* <li> have all their constraints already enforced in the subplan,
* </ul> and thus will not be needed anymore.
*
* @param onlyIfNotDetermined if true, no trimming performed unless there is at least one variable that is not functionally determined
* @return the plan after the trimming (possibly the original)
* @since 1.5
*/
public static SubPlan trimUnneccessaryVariables(SubPlanFactory planFactory, /*IOperationCompiler buildable,*/
SubPlan plan, boolean onlyIfNotDetermined, QueryAnalyzer analyzer) {
Set<PVariable> canBeTrimmed = new HashSet<PVariable>();
Set<PVariable> variablesInPlan = plan.getVisibleVariables();
for (PVariable trimCandidate : variablesInPlan) {
if (trimCandidate.getReferringConstraintsOfType(ExportedParameter.class).isEmpty()) {
if (plan.getAllEnforcedConstraints().containsAll(trimCandidate.getReferringConstraints()))
canBeTrimmed.add(trimCandidate);
}
}
final Set<PVariable> retainedVars = setMinus(variablesInPlan, canBeTrimmed);
if (!canBeTrimmed.isEmpty() && !(onlyIfNotDetermined && areVariablesDetermined(plan, retainedVars, canBeTrimmed, analyzer, false))) {
// TODO add smart ordering?
plan = planFactory.createSubPlan(new PProject(retainedVars), plan);
}
return plan;
}
/**
* @return true iff a set of given variables functionally determine all visible variables in the subplan according to the subplan's constraints
* @param strict if true, only "hard" dependencies are taken into account that are strictly enforced by the model representation;
* if false, user-provided soft dependencies are included as well, that are anticipated but not guaranteed by the storage mechanism;
* use true if superfluous dependencies may taint the correctness of a computation, false if they would merely impact performance
* @since 1.5
*/
public static boolean areAllVariablesDetermined(SubPlan plan, Collection<PVariable> determining, QueryAnalyzer analyzer, boolean strict) {
return areVariablesDetermined(plan, determining, plan.getVisibleVariables(), analyzer, strict);
}
/**
* @return true iff one set of given variables functionally determine the other set according to the subplan's constraints
* @param strict if true, only "hard" dependencies are taken into account that are strictly enforced by the model representation;
* if false, user-provided soft dependencies are included as well, that are anticipated but not guaranteed by the storage mechanism;
* use true if superfluous dependencies may taint the correctness of a computation, false if they would merely impact performance
* @since 1.5
*/
public static boolean areVariablesDetermined(SubPlan plan, Collection<PVariable> determining, Collection<PVariable> determined,
QueryAnalyzer analyzer, boolean strict) {
Map<Set<PVariable>, Set<PVariable>> dependencies = analyzer.getFunctionalDependencies(plan.getAllEnforcedConstraints(), strict);
final Set<PVariable> closure = FunctionalDependencyHelper.closureOf(determining, dependencies);
final boolean isDetermined = closure.containsAll(determined);
return isDetermined;
}
private static <T> Set<T> setMinus(Set<T> a, Set<T> b) {
Set<T> difference = new HashSet<T>(a);
difference.removeAll(b);
return difference;
}
/**
* Finds an arbitrary constraint that is not enforced at the given plan.
*
* @param pSystem
* @param plan
* @return a PConstraint that is not enforced, if any, or null if all are enforced
*/
public static PConstraint getAnyUnenforcedConstraint(PBody pSystem,
SubPlan plan) {
Set<PConstraint> allEnforcedConstraints = plan.getAllEnforcedConstraints();
Set<PConstraint> constraints = pSystem.getConstraints();
for (PConstraint pConstraint : constraints) {
if (!allEnforcedConstraints.contains(pConstraint))
return pConstraint;
}
return null;
}
/**
* Skips the last few steps, if any, that are projections, so that a custom projection can be added instead.
* Useful for connecting body final plans into the production node.
*
* @since 2.1
*/
public static SubPlan eliminateTrailingProjections(SubPlan plan) {
while (plan.getOperation() instanceof PProject)
plan = plan.getParentPlans().get(0);
return plan;
}
/**
* Verifies whether all constraints are enforced and exported parameters are present.
*
* @param pSystem
* @param plan
* @throws ViatraQueryRuntimeException
*/
public static void finalCheck(final PBody pSystem, SubPlan plan, IQueryMetaContext context) {
PConstraint unenforcedConstraint = getAnyUnenforcedConstraint(pSystem, plan);
if (unenforcedConstraint != null) {
throw new QueryProcessingException(
"Pattern matcher construction terminated without successfully enforcing constraint {1}."
+ " Could be caused if the value of some variables can not be deduced, e.g. by circularity of pattern constraints.",
new String[] { unenforcedConstraint.toString() }, "Could not enforce a pattern constraint", null);
}
for (ExportedParameter export : pSystem
.getConstraintsOfType(ExportedParameter.class)) {
if (!export.isReadyAt(plan, context)) {
throw new QueryProcessingException(
"Exported pattern parameter {1} could not be deduced during pattern matcher construction."
+ " A pattern constraint is required to positively deduce its value.",
new String[] { export.getParameterName() }, "Could not calculate pattern parameter",
null);
}
}
}
}
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