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

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