presto-postgresql/src/main/java/io/prestosql/plugin/postgresql/PostgreSqlClient.java/PostgreSqlClient/typedVarcharColumnMapping
class PostgreSqlClient:    private ColumnMapping typedVarcharColumnMapping(String jdbcTypeName)
    {
        return ColumnMapping.sliceMapping(
                VARCHAR,
                (resultSet, columnIndex) -> utf8Slice(resultSet.getString(columnIndex)),
                typedVarcharWriteFunction(jdbcTypeName));
    }