rewrite query completion

The old implementation searched for all possible values and then
executed each query to see what matches.
The new implementation uses several indices to find only
the matching values.

pdb-utils/src/main/java/org/lucares/utils/CollectionUtils.java

@@ -7,6 +7,7 @@ import java.util.List;
 import java.util.Map;
 import java.util.function.Function;
 import java.util.function.Predicate;
+import java.util.function.Supplier;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
@@ -62,4 +63,31 @@ public class CollectionUtils {
 		return collection.stream().filter(predicate).collect(Collectors.toList());
 	}
 
+	public static <T> int indexOf(final List<T> list, final Predicate<T> predicate) {
+		for (int i = 0; i < list.size(); i++) {
+			if (predicate.test(list.get(i))) {
+				return i;
+			}
+		}
+		return -1;
+	}
+
+	public static <V, T extends Collection<V>> T removeAll(final T collection, final T remove,
+			final Supplier<T> generator) {
+
+		final T result = generator.get();
+		result.addAll(collection);
+		result.removeAll(remove);
+		return result;
+	}
+
+	public static <V, T extends Collection<V>> T retainAll(final T collection, final T retain,
+			final Supplier<T> generator) {
+
+		final T result = generator.get();
+		result.addAll(collection);
+		result.retainAll(retain);
+		return result;
+	}
+
 }