--- a/Plugins/Engine/OrthancPluginDatabase.cpp	Wed Jan 02 18:39:25 2019 +0100
+++ b/Plugins/Engine/OrthancPluginDatabase.cpp	Wed Jan 02 19:04:15 2019 +0100
@@ -133,6 +133,8 @@
     answerChanges_ = NULL;
     answerExportedResources_ = NULL;
     answerDone_ = NULL;
+    answerMatchingResources_ = NULL;
+    answerMatchingInstances_ = NULL;
   }
 
 
@@ -224,15 +226,12 @@
                                                void *payload) : 
     library_(library),
     errorDictionary_(errorDictionary),
-    type_(_OrthancPluginDatabaseAnswerType_None),
     backend_(backend),
     payload_(payload),
-    listener_(NULL),
-    answerDicomMap_(NULL),
-    answerChanges_(NULL),
-    answerExportedResources_(NULL),
-    answerDone_(NULL)
+    listener_(NULL)
   {
+    ResetAnswers();
+
     memset(&extensions_, 0, sizeof(extensions_));
 
     size_t size = sizeof(extensions_);
@@ -242,6 +241,11 @@
     }
 
     memcpy(&extensions_, extensions, size);
+
+    if (extensions_.lookupResources == NULL)
+    {
+      LOG(WARNING) << "Performance warning in index plugin: Fast lookup is not available";
+    }
   }
 
 
@@ -960,6 +964,17 @@
           answerExportedResources_->clear();
           break;
 
+        case _OrthancPluginDatabaseAnswerType_MatchingResource:
+          assert(answerMatchingResources_ != NULL);
+          answerMatchingResources_->clear();
+
+          if (answerMatchingInstances_ != NULL)
+          {
+            answerMatchingInstances_->clear();
+          }
+          
+          break;
+
         default:
           throw OrthancException(ErrorCode_DatabasePlugin,
                                  "Unhandled type of answer for custom index plugin: " +
@@ -1088,6 +1103,32 @@
         break;
       }
 
+      case _OrthancPluginDatabaseAnswerType_MatchingResource:
+      {
+        const OrthancPluginMatchingResource& match = 
+          *reinterpret_cast<const OrthancPluginMatchingResource*>(answer.valueGeneric);
+
+        if (match.resourceId == NULL)
+        {
+          throw OrthancException(ErrorCode_DatabasePlugin);
+        }
+
+        assert(answerMatchingResources_ != NULL);
+        answerMatchingResources_->push_back(match.resourceId);
+
+        if (answerMatchingInstances_ != NULL)
+        {
+          if (match.someInstanceId == NULL)
+          {
+            throw OrthancException(ErrorCode_DatabasePlugin);
+          }
+
+          answerMatchingInstances_->push_back(match.someInstanceId);
+        }
+ 
+        break;
+      }
+
       default:
         throw OrthancException(ErrorCode_DatabasePlugin,
                                "Unhandled type of answer for custom index plugin: " +
@@ -1118,12 +1159,32 @@
   {
     if (extensions_.lookupResources == NULL)
     {
+      // Fallback to compatibility mode
       CompatibilityDatabaseWrapper::ApplyLookupResources
         (resourcesId, instancesId, lookup, queryLevel, limit);
     }
     else
     {
+      std::vector<OrthancPluginDatabaseConstraint> constraints;
+      std::vector< std::vector<const char*> > constraintsValues;
+
+      constraints.resize(lookup.size());
+      constraintsValues.resize(lookup.size());
+
+      for (size_t i = 0; i < lookup.size(); i++)
+      {
+        lookup[i].EncodeForPlugins(constraints[i], constraintsValues[i]);
+      }
+
+      answerMatchingResources_ = &resourcesId;
+      answerMatchingInstances_ = instancesId;
+      
       ResetAnswers();
+
+      CheckSuccess(extensions_.lookupResources(GetContext(), payload_, lookup.size(),
+                                               (lookup.empty() ? NULL : &constraints[0]),
+                                               Plugins::Convert(queryLevel),
+                                               limit, (instancesId == NULL ? 0 : 1)));
     }
   }
 

--- a/Plugins/Engine/OrthancPluginDatabase.h	Wed Jan 02 18:39:25 2019 +0100
+++ b/Plugins/Engine/OrthancPluginDatabase.h	Wed Jan 02 19:04:15 2019 +0100
@@ -70,6 +70,8 @@
     std::list<ServerIndexChange>*  answerChanges_;
     std::list<ExportedResource>*   answerExportedResources_;
     bool*                          answerDone_;
+    std::list<std::string>*        answerMatchingResources_;
+    std::list<std::string>*        answerMatchingInstances_;
 
     OrthancPluginDatabaseContext* GetContext()
     {

--- a/Plugins/Include/orthanc/OrthancCDatabasePlugin.h	Wed Jan 02 18:39:25 2019 +0100
+++ b/Plugins/Include/orthanc/OrthancCDatabasePlugin.h	Wed Jan 02 19:04:15 2019 +0100
@@ -740,7 +740,7 @@
       /* inputs */
       void* payload,
       uint32_t constraintsCount,
-      const OrthancPluginDatabaseConstraint* const* constraints,
+      const OrthancPluginDatabaseConstraint* constraints,
       OrthancPluginResourceType queryLevel,
       uint32_t limit,
       uint8_t requestSomeInstance);