Merlin Moncure <mmoncure@gmail.com> writes:
> On Wed, May 25, 2016 at 3:55 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> Andres Freund <andres@anarazel.de> writes:
>>> If we go with rewriting this into LATERAL, I'd vote for 2.5 (trailed by
>>> option 1), that'd keep most of the functionality, and would break
>>> visibly rather than invisibly in the cases where not.
>> 2.5 would be okay with me.
> Curious if this approach will also rewrite:
> select generate_series(1,generate_series(1,3)) s;
> ...into
> select s from generate_series(1,3) x cross join lateral generate_series(1,x) s;
Yeah, that would be the idea.
> another interesting case today is:
> create sequence s;
> select generate_series(1,nextval('s')), generate_series(1,nextval('s'));
> this statement never terminates. a lateral rewrite of this query
> would always terminate with much better defined and well understood
> behaviors -- this is good.
Interesting example demonstrating that 100% bug compatibility is not
possible. But as you say, most people would probably prefer the other
behavior anyhow.
regards, tom lane