Re: pgsql: Further tweaking of print_aligned_vertical().

Greg Stark <stark(at)mit(dot)edu> writes:
> On 1 Dec 2015 19:48, "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> In passing, avoid possible calculation of log10(0). Probably that's
>> harmless, given the lack of field complaints, but it seems risky:
>> conversion of NaN to an integer isn't well defined.

> Am I going to have to fire up the emulator again?

No, 'cause I fixed it ;-). I initially thought that the case might
be unreachable, but it isn't: you can get there with cont->nrows == 0
if you have FETCH_SIZE set and the resultset size is an exact multiple
of FETCH_SIZE.

While poking at that, though, I ran into yet another bug in this code:

regression=# \pset format wrapped
Output format is wrapped.
regression=# \x
Expanded display is on.
regression=# select repeat('xyzzy',22) from generate_series(1,25);
-[ RECORD 1 ]------------------------------------------------------------------
repeat | xyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzy.
|.xyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzy
-[ RECORD 2 ]------------------------------------------------------------------
repeat | xyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzy.
|.xyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzy
.. etc etc ...

regression=# \set FETCH_COUNT 2
regression=# select repeat('xyzzy',22) from generate_series(1,25);
-[ RECORD 1 ]-------------------------------------------------------------------
---------------------------------------
repeat | xyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzyx
yzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzy
-[ RECORD 2 ]-------------------------------------------------------------------
---------------------------------------
repeat | xyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzyx
yzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzy
.. etc etc ...

That is, wrap width determination is broken the moment you set FETCH_SIZE.

The reason seems to be this ugly kluge in ExecQueryUsingCursor():

else if (pset.queryFout == stdout && !did_pager)
{
/*
* If query requires multiple result sets, hack to ensure that
* only one pager instance is used for the whole mess
*/
pset.queryFout = PageOutput(100000, &(my_popt.topt));
did_pager = true;
}

After we have run that code, pset.queryFout is no longer pointing at
stdout, which breaks every single one of the "fout == stdout" tests in
print.c. It'd be all right if those tests knew that they were dealing
with an is_pager situation, but they don't because that critical piece of
information is not passed down to printQuery(). I think we could probably
fix this by making is_pager an additional argument of printQuery() and its
relevant subroutines.

regards, tom lane