Remove entries from geospatial index (#633).

Once a Geo Coordinate topic is deleted (e.g. when an Address is deleted) the corresponding entry is removed from the geospatial index.

NOTE: this module is still experimental. Only use it with a testing DB.

See #633.

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CORRECT COMMIT MESSAGE FOR PREVIOUS COMMIT:

Update geospatial index (#633).

Once a Geo Coordinate topic changes (e.g. when an Address is changed) the geospatial index is updated accordingly.

See #633.

src/main/java/de/deepamehta/plugins/geospatial/GeospatialPlugin.java

@@ -13,6 +13,7 @@
 import de.deepamehta.core.service.annotation.ConsumesService;
 import de.deepamehta.core.service.event.PostCreateTopicListener;
 import de.deepamehta.core.service.event.PostUpdateTopicListener;
+import de.deepamehta.core.service.event.PreDeleteTopicListener;
 
 import org.neo4j.graphdb.Node;
 import org.neo4j.graphdb.GraphDatabaseService;
@@ -48,7 +49,8 @@
 @Produces("application/json")
 public class GeospatialPlugin extends PluginActivator implements GeospatialService, PointFactory,
                                                                                     PostCreateTopicListener,
-                                                                                    PostUpdateTopicListener {
+                                                                                    PostUpdateTopicListener,
+                                                                                    PreDeleteTopicListener {
 
     // ------------------------------------------------------------------------------------------------------- Constants
 
@@ -123,6 +125,9 @@ public void init() {
         GraphDatabaseService neo4j = (GraphDatabaseService) dms.getDatabaseVendorObject();
         SpatialDatabaseService spatialDB = new SpatialDatabaseService(neo4j);
         //
+        // IMPORTANT: deleting a Neo4j Spatial layer includes deleting the geometry nodes which are at the same time
+        // our Geo Coordinate topics. This results in a corrupted DM database as associations with only 1 player remain.
+        // --> Never delete a layer!!!
         // spatialDB.deleteLayer(DEFAULT_LAYER_NAME, new NullListener());
         //
         if (spatialDB.containsLayer(DEFAULT_LAYER_NAME)) {
@@ -178,6 +183,17 @@ public void postUpdateTopic(Topic topic, TopicModel newModel, TopicModel oldMode
         }
     }
 
+    // ---
+
+    @Override
+    public void preDeleteTopic(Topic topic, Directives directives) {
+        if (topic.getTypeUri().equals("dm4.geomaps.geo_coordinate")) {
+            logger.info("########## A Geo Coordinate topic was deleted: " + topic);
+            layer.removeFromIndex(topic.getId());
+            logger.info("########## Geo Coordinate " + topic.getId() + " removed from geospatial index");
+        }
+    }
+
 
 
     // ------------------------------------------------------------------------------------------------- Private Methods