fix limit by does not work anymore

pdb-plotting/src/main/java/org/lucares/recommind/logs/Plotter.java

@@ -76,6 +76,12 @@ public class Plotter {
 
             final Result result = db.get(new Query(query, dateRange), groupBy);
 
+            if (result.getGroups().size() > 100 && plotSettings.getLimitBy() == Limit.NO_LIMIT) {
+                throw new RuntimeException("too many groups - try adding restrictions for one of these fields "
+                        + String.join(",", groupBy) + ".For example '" + query + " and " + groupBy.get(0)
+                        + "=someValue'. Or you can remove a field from 'Group By'.");
+            }
+
             final long start = System.nanoTime();
             final AtomicInteger idCounter = new AtomicInteger(0);
             result.getGroups().stream().parallel().forEach(groupResult -> {