presto-main/src/main/java/io/prestosql/operator/index/IndexBuildDriverFactoryProvider.java/IndexBuildDriverFactoryProvider/createSnapshot
class IndexBuildDriverFactoryProvider:    public DriverFactory createSnapshot(int pipelineId, IndexSnapshotBuilder indexSnapshotBuilder)
    {
        checkArgument(indexSnapshotBuilder.getOutputTypes().equals(outputTypes));
        return new DriverFactory(
                pipelineId,
                inputDriver,
                false,
                ImmutableList.<OperatorFactory>builder()
                        .addAll(coreOperatorFactories)
                        .add(new PagesIndexBuilderOperatorFactory(outputOperatorId, planNodeId, indexSnapshotBuilder))
                        .build(),
                OptionalInt.empty(),
                UNGROUPED_EXECUTION);
    }