Re: pg_generate_sequence and info_schema patch (Was: SELECT

Tom Lane wrote:
> Joe Conway <mail(at)joeconway(dot)com> writes:
>>regression=# select * from pg_generate_sequence(8, 4);
>>ERROR: finish is less than start
>
> Hm, would it be better just to return an empty set? Certainly I'd
> expect pg_generate_sequence(1,0) to return an empty set with no error.

OK -- for this and other concerns below, I bit the bullet and decided to
support descending series and step sizes other than one. Now it does this:

regression=# select * from generate_series(8, 4);
generate_series
-----------------
8
7
6
5
4
(5 rows)

regression=# select * from generate_series(8, 4, 2);
generate_series
-----------------
8
6
4
(3 rows)

regression=# select * from generate_series(8000000000, 8000000004, 2);
generate_series
-----------------
8000000000
8000000002
8000000004
(3 rows)

regression=# select * from generate_series(8000000004, 8000000000, 3);
generate_series
-----------------
8000000004
8000000001
(2 rows)

regression=# select * from generate_series(8000000004, 8000000000, -3);
ERROR: step value must be greater than 0
HINT: Use start greater than finish to create a descending series.

>>regression=# select * from pg_generate_sequence(3,8000000000);
>>ERROR: range of start to finish is too large
>>HINT: start to finish range must be less than 4294967295
>
> Is there a good reason for that restriction? (I've never thought it was
> good design for the SRF API to assume that the number of iterations
> could be determined in advance, anyway.)

See above -- fixed. But I'm not going to try to return > 4 billion
values to illustrate ;-)

> Actually I think you could leave off the pg_ prefix
> and just make it generate_series or generate_set.

OK -- made it generate_series().

> Maybe the best documentation answer is to create a new subsection in the
> Functions chapter. This may be our first standard set-returning
> function but I bet it will not be the last, so the shortness of the
> subsection doesn't bother me.

Agreed. I'll start this post-superbowl :-)

I'll apply in 24-48 hours if there are no further comments.

Thanks,

Joe

p.s. I did a `make distclean` prior to creating the attached diff. Do
the lines at the top, e.g.:
? src/bin/pg_id/.deps
? src/bin/pg_id/pg_id
...
indicate stuff not being cleaned up when it ought to be?