bundles/org.simantics.db.impl/src/org/simantics/db/impl/query/ExternalReadEntry.java

   1 /*******************************************************************************
   2  * Copyright (c) 2007, 2018 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.impl.query;
  13
  14 import java.util.LinkedList;
  15
  16 import org.simantics.db.exception.DatabaseException;
  17 import org.simantics.db.impl.DebugPolicy;
  18 import org.simantics.db.impl.graph.ReadGraphImpl;
  19 import org.simantics.db.procedure.AsyncProcedure;
  20 import org.simantics.db.request.ExternalRead;
  21 import org.simantics.db.request.RequestFlags;
  22
  23 final public class ExternalReadEntry<T> extends CacheEntryBase<AsyncProcedure<T>> {
  24
  25     final LinkedList<T> items = new LinkedList<T>();
  26
  27     protected ExternalRead<T> request;
  28
  29     @Override
  30     int makeHash() {
  31         return request.hashCode();
  32     }
  33
  34     @Override
  35     public Object getOriginalRequest() {
  36         return request;
  37     }
  38
  39     @Override
  40     public void clearResult(QuerySupport support) {
  41     }
  42
  43     @Override
  44     public void discard() {
  45         request.unregistered();
  46         request = null;
  47         super.discard();
  48     }
  49
  50     @Override
  51     public void setPending() {
  52         //if(result != NO_RESULT) {
  53             //new Exception("result = " + result).printStackTrace();
  54         //}
  55         statusOrException = PENDING;
  56         result = REQUIRES_COMPUTATION;
  57     }
  58
  59     public ExternalReadEntry(ExternalRead<T> request) {
  60         assert request != null;
  61         this.request = request;
  62     }
  63
  64     final public void queue(T item) {
  65         synchronized(items) {
  66                 items.addLast(item);
  67                 // TODO: implement flags/logic in ExternalRead to state that all but the latest request result can be evaporated
  68                 // In some cases where data is produced really fast this might be necessary but currently this queueing will do.
  69         }
  70     }
  71
  72     final public void addOrSet(QueryProcessor processor, Object item) {
  73
  74         try {
  75
  76             assert(isPending());
  77
  78             //ArrayList<Procedure<T>> p = null;
  79
  80             synchronized(this) {
  81
  82                 setResult(item);
  83                 setReady();
  84 //                p = procs;
  85 //                procs = null;
  86
  87             }
  88
  89 //            if(p != null)
  90 //                for(Procedure proc : p) {
  91 //                    proc.execute((T)item);
  92 //                }
  93
  94         } catch (Throwable t) {
  95             t.printStackTrace();
  96         }
  97
  98     }
  99
 100     @Override
 101     public void except(Throwable t) {
 102         if(DebugPolicy.QUERY_STATE) System.out.println("[QUERY STATE]: excepted " + this);
 103         if(statusOrException != DISCARDED) {
 104             statusOrException = EXCEPTED;
 105             result = t;
 106         } else {
 107             result = t;
 108         }
 109         assert(isExcepted());
 110     }
 111
 112     @Override
 113     public void setResult(Object result) {
 114         super.setResult(result);
 115         assert(!(result instanceof Throwable));
 116         assert(!isExcepted());
 117     }
 118
 119     @Override
 120     final public Query getQuery() {
 121
 122         return new Query() {
 123
 124                         @Override
 125                         public void recompute(ReadGraphImpl graph) {
 126
 127                                 synchronized(items) {
 128
 129
 130                                         // Update
 131                                         if(!items.isEmpty()) {
 132                                             setReady();
 133                                                 setResult(items.removeFirst());
 134                                         }
 135                                         // Reschedule
 136                                         if(!items.isEmpty()) {
 137                                                 graph.processor.updatePrimitive(request);
 138                                         }
 139
 140                                 }
 141
 142                         }
 143
 144                         @Override
 145                         public void removeEntry(QueryProcessor processor) {
 146                                 processor.cache.remove(ExternalReadEntry.this);
 147                         }
 148
 149                         @Override
 150                         public int type() {
 151                                 return RequestFlags.IMMEDIATE_UPDATE;
 152                         }
 153
 154                         @Override
 155                         public String toString() {
 156                                 if(request == null) return "DISCARDED ExternalRead";
 157                                 else return request.toString();
 158                         }
 159
 160         };
 161
 162     }
 163
 164         @Override
 165         public String toString() {
 166                 if(request == null) return "DISCARDED ExternalRead " + System.identityHashCode(this);
 167                 else return request.toString() + " " + + System.identityHashCode(this);
 168         }
 169
 170     @Override
 171     public Object performFromCache(ReadGraphImpl graph, AsyncProcedure<T> procedure) {
 172
 173         AsyncProcedure<T> proc = (AsyncProcedure<T>)procedure;
 174
 175             if(isExcepted()) {
 176
 177             proc.exception(graph, (Throwable)getResult());
 178
 179         } else {
 180
 181             proc.execute(graph, (T)getResult());
 182
 183         }
 184
 185             return getResult();
 186
 187     }
 188
 189     @Override
 190     void prepareRecompute(QuerySupport querySupport) {
 191         // Do nothing - the state is already set and cannot be recomputed on demand
 192     }
 193
 194     public Object compute(ReadGraphImpl graph, AsyncProcedure<T> procedure) throws DatabaseException {
 195         return graph.processor.cache.performQuery(graph, request, this, procedure);
 196     }
 197
 198 }