Kevin Grittner <kgrittn@gmail.com> writes:
> On Fri, Sep 2, 2016 at 9:25 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> ORDER BY is not a useful suggestion when there is nothing
>> you could order by to get the old behavior.
> I'm apparently missing something, because I see a column with the
> header "generate_series" in the result set.
You are apparently only thinking about generate_series and not any
other SRF. Other SRFs don't necessarily produce outputs that are
in a nice sortable order. Even for one that does, sorting by it
would destroy the existing behavior:
regression=# select *, generate_series(1,3) from int8_tbl; q1 | q2 | generate_series
------------------+-------------------+----------------- 123 | 456 | 1
123 | 456 | 2 123 | 456 | 3 123 |
4567890123456789| 1 123 | 4567890123456789 | 2 123 |
4567890123456789| 34567890123456789 | 123 | 14567890123456789 |
123| 24567890123456789 | 123 | 34567890123456789 | 4567890123456789 |
14567890123456789 | 4567890123456789 | 24567890123456789 | 4567890123456789 |
34567890123456789| -4567890123456789 | 14567890123456789 | -4567890123456789 |
24567890123456789| -4567890123456789 | 3
(15 rows)
Now you could argue that the ordering of the table rows
themselves is poorly defined, and you'd be right, but that
doesn't change the fact that the generate_series output
has a well-defined repeating sequence. People might be
relying on that property.
regards, tom lane