#470: create tag-translator eagerly

Author: mmerdes

oshdb-api/src/main/java/org/heigit/ohsome/oshdb/api/db/OSHDBJdbc.java

@@ -30,7 +30,7 @@ public class OSHDBJdbc extends OSHDBDatabase {
 
   protected final DataSource dataSource;
   protected final DataSource keytablesSource;
-  protected JdbcTagTranslator tagTranslator;
+  protected final TagTranslator tagTranslator;
   private boolean useMultithreading = true;
 
   public OSHDBJdbc(DataSource source) {
@@ -40,13 +40,11 @@ public OSHDBJdbc(DataSource source) {
   public OSHDBJdbc(DataSource source, DataSource keytables) {
     this.dataSource = source;
     this.keytablesSource = keytables;
+    this.tagTranslator = new JdbcTagTranslator(keytablesSource);
   }
 
   @Override
   public TagTranslator getTagTranslator() {
-    if (tagTranslator == null) {
-      tagTranslator = new JdbcTagTranslator(keytablesSource);
-    }
     return tagTranslator;
   }