bundles/org.simantics.db.layer0/src/org/simantics/db/layer0/genericrelation/combinators/Intersection.java

   1 /*******************************************************************************
   2  * Copyright (c) 2007, 2010 Association for Decentralized Information Management
   3  * in Industry THTH ry.
   4  * All rights reserved. This program and the accompanying materials
   5  * are made available under the terms of the Eclipse Public License v1.0
   6  * which accompanies this distribution, and is available at
   7  * http://www.eclipse.org/legal/epl-v10.html
   8  *
   9  * Contributors:
  10  *     VTT Technical Research Centre of Finland - initial API and implementation
  11  *******************************************************************************/
  12 package org.simantics.db.layer0.genericrelation.combinators;
  13
  14 import java.util.ArrayList;
  15 import java.util.Collection;
  16 import java.util.List;
  17
  18 import org.simantics.db.ReadGraph;
  19 import org.simantics.db.exception.DatabaseException;
  20 import org.simantics.db.layer0.adapter.GenericRelation;
  21 import org.simantics.db.layer0.genericrelation.AbstractRelation;
  22 import org.simantics.utils.datastructures.Pair;
  23
  24 /**
  25  * Takes the intersection of multiple relations.
  26  */
  27 public class Intersection extends AbstractRelation {
  28
  29         GenericRelation realizable = null;
  30         Collection<GenericRelation> constraints;
  31
  32         public Intersection(Collection<GenericRelation> relations) {
  33                 for(GenericRelation relation : relations)
  34                         if(realizable == null && relation.isRealizable()) {
  35                                 realizable = relation;
  36                         }
  37                         else
  38                                 constraints.add(relation);
  39         }
  40
  41         public Intersection(GenericRelation realizable, Collection<GenericRelation> constraints) {
  42                 assert(realizable.isRealizable());
  43                 this.realizable = realizable;
  44                 this.constraints = constraints;
  45         }
  46
  47         @Override
  48         public boolean contains(ReadGraph g, Object[] tuple) throws DatabaseException {
  49                 if(!realizable.contains(g, tuple))
  50                         return false;
  51                 for(GenericRelation relation : constraints)
  52                         if(!relation.contains(g, tuple))
  53                                 return false;
  54                 return true;
  55         }
  56
  57         @Override
  58         public boolean isRealizable() {
  59                 return realizable != null;
  60         }
  61
  62         @Override
  63         public List<Object[]> realize(ReadGraph g) throws DatabaseException {
  64                 ArrayList<Object[]> result = new ArrayList<Object[]>();
  65                 loop:
  66                 for(Object[] tuple : realizable.realize(g)) {
  67                         for(GenericRelation constraint : constraints)
  68                                 if(!constraint.contains(g, tuple))
  69                                         continue loop;
  70                         result.add(tuple);
  71                 }
  72                 return result;
  73         }
  74
  75         // TODO optimize select
  76
  77         @Override
  78         public GenericRelation selectByRelation(String bindingPattern,
  79                         GenericRelation constraint) {
  80                 if(realizable != null)
  81                         return new Intersection(realizable.selectByRelation(bindingPattern, constraint),
  82                                         constraints);
  83                 else
  84                         return super.selectByRelation(bindingPattern, constraint);
  85         }
  86
  87         @Override
  88         public Pair<String, String>[] getFields() {
  89                 if(realizable != null)
  90                         return realizable.getFields();
  91                 for(GenericRelation relation : constraints)
  92                         return relation.getFields();
  93                 return null;
  94         }
  95
  96 }