presto-base-jdbc/src/main/java/io/prestosql/plugin/jdbc/BaseJdbcClient.java/BaseJdbcClient/getSplits
class BaseJdbcClient:    @Override
    public ConnectorSplitSource getSplits(JdbcIdentity identity, JdbcTableHandle tableHandle)
    {
        return new FixedSplitSource(ImmutableList.of(new JdbcSplit(Optional.empty())));
    }