[441323] Added support for search operations to cache results

The proposed cache implementations are simple; one of them is bound to
the backend, while the other is reset after each pattern match process.

Change-Id: I177295cd26e0fbfa574936a7ed959bacb827b9ae
Signed-off-by: Zoltan Ujhelyi <ujhelyiz@incquerylabs.com>

6 files changed, 156 insertions, 9 deletions

diff --git a/query/plugins/org.eclipse.viatra.query.runtime.localsearch/.settings/.api_filters b/query/plugins/org.eclipse.viatra.query.runtime.localsearch/.settings/.api_filters
index 354f0882e..846be8c7d 100644
--- a/query/plugins/org.eclipse.viatra.query.runtime.localsearch/.settings/.api_filters
+++ b/query/plugins/org.eclipse.viatra.query.runtime.localsearch/.settings/.api_filters
@@ -1,5 +1,34 @@
 <?xml version="1.0" encoding="UTF-8" standalone="no"?>
 <component id="org.eclipse.viatra.query.runtime.localsearch" version="2">
+    <resource path="src/org/eclipse/viatra/query/runtime/localsearch/matcher/ISearchContext.java" type="org.eclipse.viatra.query.runtime.localsearch.matcher.ISearchContext$SearchContext">
+        <filter id="338722907">
+            <message_arguments>
+                <message_argument value="org.eclipse.viatra.query.runtime.localsearch.matcher.ISearchContext.SearchContext"/>
+                <message_argument value="SearchContext(IBaseIndex, IQueryResultProviderAccess, QueryEvaluationHint)"/>
+            </message_arguments>
+        </filter>
+        <filter comment="Internal API implementation" id="576725006">
+            <message_arguments>
+                <message_argument value="ISearchContext"/>
+                <message_argument value="SearchContext"/>
+            </message_arguments>
+        </filter>
+    </resource>
+    <resource path="src/org/eclipse/viatra/query/runtime/localsearch/matcher/integration/LocalSearchBackend.java" type="org.eclipse.viatra.query.runtime.localsearch.matcher.integration.LocalSearchBackend">
+        <filter comment="Internal API usage" id="640708718">
+            <message_arguments>
+                <message_argument value="PurgableCache()"/>
+                <message_argument value="LocalSearchBackend"/>
+            </message_arguments>
+        </filter>
+        <filter comment="Internal API usage" id="640712815">
+            <message_arguments>
+                <message_argument value="PurgableCache"/>
+                <message_argument value="LocalSearchBackend"/>
+                <message_argument value="purge()"/>
+            </message_arguments>
+        </filter>
+    </resource>
     <resource path="src/org/eclipse/viatra/query/runtime/localsearch/operations/CallOperationHelper.java" type="org.eclipse.viatra.query.runtime.localsearch.operations.CallOperationHelper$PatternCall">
         <filter id="643846161">
             <message_arguments>
diff --git a/query/plugins/org.eclipse.viatra.query.runtime.localsearch/src/org/eclipse/viatra/query/runtime/localsearch/matcher/ISearchContext.java b/query/plugins/org.eclipse.viatra.query.runtime.localsearch/src/org/eclipse/viatra/query/runtime/localsearch/matcher/ISearchContext.java
index ddefd91d6..d8038c7b0 100644
--- a/query/plugins/org.eclipse.viatra.query.runtime.localsearch/src/org/eclipse/viatra/query/runtime/localsearch/matcher/ISearchContext.java
+++ b/query/plugins/org.eclipse.viatra.query.runtime.localsearch/src/org/eclipse/viatra/query/runtime/localsearch/matcher/ISearchContext.java
@@ -32,15 +32,24 @@ import org.eclipse.viatra.query.runtime.matchers.context.IQueryResultProviderAcc
 import org.eclipse.viatra.query.runtime.matchers.planning.QueryProcessingException;
 import org.eclipse.viatra.query.runtime.matchers.psystem.queries.PParameter;
 import org.eclipse.viatra.query.runtime.matchers.psystem.queries.PQuery;
+import org.eclipse.viatra.query.runtime.matchers.util.PurgableCache;
+import org.eclipse.viatra.query.runtime.matchers.util.ICache;
+import org.eclipse.viatra.query.runtime.matchers.util.IProvider;
 
 /**
  * The {@link ISearchContext} interface allows search operations to reuse platform services such as the indexer.
  * 
  * @author Zoltan Ujhelyi
+ * @noreference This interface is not intended to be referenced by clients.
+ * @noimplement This interface is not intended to be implemented by clients.
+ * @noextend This interface is not intended to be extended by clients.
  *
  */
 public interface ISearchContext{
     
+    /**
+     * Provides access to the EMF-specific base index for search operation; do not use if not on EMF Scope
+     */
     NavigationHelper getBaseIndex();
     
     /**
@@ -59,22 +68,36 @@ public interface ISearchContext{
      */
     IQueryResultProvider getMatcher(MatcherReference reference) throws LocalSearchException;
     
+    /**
+     * Allows search operations to cache values through the entire lifecycle of the local search backend. The values are
+     * calculated if not cached before using the given provider, or returned from the cache accordingly.
+     * 
+     * @since 1.7
+     */
+    <T> T accessBackendLevelCache(Object key, Class<? extends T> clazz, IProvider<T> valueProvider);
+    
+    /**
+     * @noreference This class is not intended to be referenced by clients.
+     * @noimplement This interface is not intended to be implemented by clients.
+     * @noextend This interface is not intended to be extended by clients.
+     */
     public class SearchContext implements ISearchContext {
 
         final NavigationHelper navigationHelper;
         final IQueryResultProviderAccess resultProviderAccess;
         final QueryEvaluationHint overrideHints;
         
+        final ICache backendLevelCache;
+        
         final Logger logger = Logger.getLogger(getClass());
         
-        /**
-         * @since 1.5
-         */
-        public SearchContext(IBaseIndex baseIndex, IQueryResultProviderAccess resultProviderAccess, QueryEvaluationHint overrideHints) throws ViatraQueryException {
             //XXX this is a problematic (and in long-term unsupported) solution, see bug 456815
+        public SearchContext(IBaseIndex baseIndex, IQueryResultProviderAccess resultProviderAccess, QueryEvaluationHint overrideHints, ICache backendLevelCache) throws ViatraQueryException {
             this.navigationHelper = ((EMFBaseIndexWrapper)baseIndex).getNavigationHelper();
             this.resultProviderAccess = resultProviderAccess;
             this.overrideHints = overrideHints;
+            
+            this.backendLevelCache = backendLevelCache;
         }
 
         public void registerObservedTypes(Set<EClass> classes, Set<EDataType> dataTypes, Set<EStructuralFeature> features) {
@@ -119,6 +142,11 @@ public interface ISearchContext{
                 throw new LocalSearchException("Could not access referenced query: "+reference, e);
             }
         }
+
+        @Override
+        public <T> T accessBackendLevelCache(Object key, Class<? extends T> clazz, IProvider<T> valueProvider) {
+            return backendLevelCache.getValue(key, clazz, valueProvider);
+        }
         
     }
 }
diff --git a/query/plugins/org.eclipse.viatra.query.runtime.localsearch/src/org/eclipse/viatra/query/runtime/localsearch/matcher/integration/LocalSearchBackend.java b/query/plugins/org.eclipse.viatra.query.runtime.localsearch/src/org/eclipse/viatra/query/runtime/localsearch/matcher/integration/LocalSearchBackend.java
index c7e7c46cc..0441b7f7b 100644
--- a/query/plugins/org.eclipse.viatra.query.runtime.localsearch/src/org/eclipse/viatra/query/runtime/localsearch/matcher/integration/LocalSearchBackend.java
+++ b/query/plugins/org.eclipse.viatra.query.runtime.localsearch/src/org/eclipse/viatra/query/runtime/localsearch/matcher/integration/LocalSearchBackend.java
@@ -29,6 +29,8 @@ import org.eclipse.viatra.query.runtime.matchers.context.IQueryRuntimeContext;
 import org.eclipse.viatra.query.runtime.matchers.planning.QueryProcessingException;
 import org.eclipse.viatra.query.runtime.matchers.psystem.analysis.QueryAnalyzer;
 import org.eclipse.viatra.query.runtime.matchers.psystem.queries.PQuery;
+import org.eclipse.viatra.query.runtime.matchers.util.ICache;
+import org.eclipse.viatra.query.runtime.matchers.util.PurgableCache;
 
 import com.google.common.collect.ArrayListMultimap;
 import com.google.common.collect.HashBasedTable;
@@ -48,7 +50,8 @@ public class LocalSearchBackend implements IQueryBackend {
     private final Set<ILocalSearchAdapter> adapters = Sets.newHashSet();
     
     // Cache
-    Table<EDataType, EClass, Set<EAttribute>> eAttributesByTypeForEClass;
+    private final Table<EDataType, EClass, Set<EAttribute>> eAttributesByTypeForEClass;
+    private final PurgableCache generalCache;
     
     private final Multimap<PQuery, LocalSearchResultProvider> resultProviderCache = ArrayListMultimap.create();
     
@@ -59,6 +62,7 @@ public class LocalSearchBackend implements IQueryBackend {
         super();
         this.context = context;
         this.eAttributesByTypeForEClass = HashBasedTable.create();
+        this.generalCache = new PurgableCache();
         this.planProvider = new CachingPlanProvider(context.getLogger());
     }
 
@@ -96,6 +100,7 @@ public class LocalSearchBackend implements IQueryBackend {
     public void dispose() {  
         eAttributesByTypeForEClass.clear();
         resultProviderCache.clear();
+        generalCache.purge();
     }
 
     @Override
@@ -163,4 +168,12 @@ public class LocalSearchBackend implements IQueryBackend {
         return context;
     }
     
+    /**
+     * Returns the internal cache of the backend
+     * @since 1.7
+     * @noreference This method is not intended to be referenced by clients.
+     */
+    public ICache getCache() {
+        return generalCache;
+    }
 }
diff --git a/query/plugins/org.eclipse.viatra.query.runtime.localsearch/src/org/eclipse/viatra/query/runtime/localsearch/matcher/integration/LocalSearchResultProvider.java b/query/plugins/org.eclipse.viatra.query.runtime.localsearch/src/org/eclipse/viatra/query/runtime/localsearch/matcher/integration/LocalSearchResultProvider.java
index 3ce483ad1..db1b2817a 100644
--- a/query/plugins/org.eclipse.viatra.query.runtime.localsearch/src/org/eclipse/viatra/query/runtime/localsearch/matcher/integration/LocalSearchResultProvider.java
+++ b/query/plugins/org.eclipse.viatra.query.runtime.localsearch/src/org/eclipse/viatra/query/runtime/localsearch/matcher/integration/LocalSearchResultProvider.java
@@ -164,8 +164,9 @@ public class LocalSearchResultProvider implements IQueryResultProvider {
         this.planProvider = planProvider;
         this.userHints = userHints;
         this.runtimeContext = context.getRuntimeContext();
+        
         try {
-            searchContext = new ISearchContext.SearchContext(engine.getBaseIndex(), resultProviderAccess, userHints);
+            searchContext = new ISearchContext.SearchContext(engine.getBaseIndex(), resultProviderAccess, userHints, backend.getCache());
         } catch (ViatraQueryException e) {
             throw new QueryProcessingException("Could not create search context for {1}", new String[]{query.getFullyQualifiedName()}, e.getMessage(), query, e);
         }
@@ -273,9 +274,7 @@ public class LocalSearchResultProvider implements IQueryResultProvider {
     private LocalSearchMatcher initializeMatcher(Object[] parameters) {
         try {
             return newLocalSearchMatcher(parameters);
-        } catch (QueryProcessingException e) {
-            throw new RuntimeException(e);
-        } catch (ViatraQueryException e) {
+        } catch (QueryProcessingException | ViatraQueryException e) {
             throw new RuntimeException(e);
         }
 
diff --git a/query/plugins/org.eclipse.viatra.query.runtime.matchers/src/org/eclipse/viatra/query/runtime/matchers/util/ICache.java b/query/plugins/org.eclipse.viatra.query.runtime.matchers/src/org/eclipse/viatra/query/runtime/matchers/util/ICache.java
new file mode 100644
index 000000000..a35c9f87b
--- /dev/null
+++ b/query/plugins/org.eclipse.viatra.query.runtime.matchers/src/org/eclipse/viatra/query/runtime/matchers/util/ICache.java
@@ -0,0 +1,31 @@
+/*******************************************************************************
+ * Copyright (c) 2010-2017, Zoltan Ujhelyi, IncQuery Labs Ltd.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *   Zoltan Ujhelyi - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.viatra.query.runtime.matchers.util;
+
+/**
+ * A cache is a simple key-value pair that stores calculated values for specific key objects
+ * 
+ * <p>
+ * <b>NOTE</b> These caches are not expected to be used outside query backend implementations 
+ * 
+ * @author Zoltan Ujhelyi
+ * @since 1.7
+ * @noreference This interface is not intended to be referenced by clients.
+ */
+public interface ICache {
+
+    /**
+     * Return a selected value for the key object. If the value is not available in the cache yet, the given provider is
+     * called once
+     */
+    <T> T getValue(Object key, Class<? extends T> clazz, IProvider<T> valueProvider);
+
+}
\ No newline at end of file
diff --git a/query/plugins/org.eclipse.viatra.query.runtime.matchers/src/org/eclipse/viatra/query/runtime/matchers/util/PurgableCache.java b/query/plugins/org.eclipse.viatra.query.runtime.matchers/src/org/eclipse/viatra/query/runtime/matchers/util/PurgableCache.java
new file mode 100644
index 000000000..6073dddb7
--- /dev/null
+++ b/query/plugins/org.eclipse.viatra.query.runtime.matchers/src/org/eclipse/viatra/query/runtime/matchers/util/PurgableCache.java
@@ -0,0 +1,47 @@
+/*******************************************************************************
+ * Copyright (c) 2010-2017, Zoltan Ujhelyi, IncQuery Labs Ltd.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *   Zoltan Ujhelyi - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.viatra.query.runtime.matchers.util;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import com.google.common.base.Preconditions;
+
+/**
+ * @author Zoltan Ujhelyi
+ * @since 1.7
+ * @noreference This class is not intended to be referenced by clients.
+ */
+public class PurgableCache implements ICache {
+
+    Map<Object, Object> storage = new HashMap<>();
+    
+    @Override
+    @SuppressWarnings("unchecked")
+    public <T> T getValue(Object key, Class<? extends T> clazz, IProvider<T> valueProvider) {
+        if (storage.containsKey(key)) {
+            Object value = storage.get(key);
+            Preconditions.checkState(clazz.isInstance(value), "Cache stores for key %s a value of %s that is incompatible with the requested type %s", key, value, clazz);
+            return (T) value;
+        } else {
+            T value = valueProvider.get();
+            storage.put(key, value);
+            return value;
+        }
+    }
+    
+    /**
+     * Removes all values stored in the cache
+     */
+    public void purge() {
+        storage.clear();
+    }
+}