log time of query execution

performanceDb/src/main/java/org/lucares/performance/db/PerformanceDb.java

@@ -150,13 +150,14 @@ public class PerformanceDb implements AutoCloseable {
 	 * @return {@link Result}
 	 */
 	public Result get(final String query, final List<String> groupBy) {
-
+		final long start = System.nanoTime();
 		final List<PdbFile> pdbFiles = tagsToFile.getFilesForQuery(query);
 
 		final Grouping grouping = Grouping.groupBy(pdbFiles, groupBy);
 
 		final Result result = toResult(grouping);
-
+		METRICS_LOGGER.debug("query execution took: " + (System.nanoTime() - start) / 1_000_000.0
+				+ "ms: " + query + " ("+groupBy+"): files found: " + pdbFiles.size());
 		return result;
 	}