[postgis-users] Re: two different geometries with the same Astext

[Miguel de la Fuente]

Well, the thing is that using dropbbox it works well. Thank you for
your suggestion.
So, what was the problem? why it fail using bounding boxes? and why
when I reload from the backup works?
I'm asking all this questions because I've got to make many queries of
this kind, and in this case I saw it because a query gave me a result
that had no sense, now I don't know if I'll have to use always
dropbbox() or hardly check the result


On 7/19/05, strk at refractions.net <strk at refractions.net> wrote:
> Would you try within(dropbbox(g1), dropbbox(g2)) ?
> You would be skipping a bbox-based short-circuit test in postgis,
> which is the only thing comes to my mind in your latest dump/reload
> example.
> 
> --strk;
> 
> On Tue, Jul 19, 2005 at 10:35:36AM -0300, Miguel de la Fuente wrote:
> > Thanks to everybory for your answers.
> >
> > I'll try to make a better description of the problem an what I made
> > related to your answer.
> >
> > To simplify the problem for you to analize it, I first extracted an
> > example from the source tables to a new table with a SELECT command:
> >
> > select
> > a.the_geom as g1,
> > b.the_geom as g2
> > into pru
> > from p107_fm_co a, p107_mz_co b
> > where a.gid=618 and b.gid=2
> >
> > and the I ran the following
> >
> > select astext(g1),astext(g2),
> > within(geometryfromtext(astext(g1)),geometryfromtext(astext(g2)))as w1,
> > within(g1,g2) as w2
> > from pru
> >
> > and I got
> >
> > --"MULTILINESTRING((5256301.4 6014697.56,5256369.25
> > 6014741.46))";"MULTILINESTRING((5256369.25 6014741.46,5256456.23
> > 6014607.03,5256388.39 6014563.13,5256301.4 6014697.56,5256369.25
> > 6014741.46))";t;f
> >
> > as you could see the first within return TRUE and the second return
> > FALSE and that is what I can't understand
> 
> >
> > But, the worst thing of all is that when I made a backup of the table
> > to attach it this message I got this:
> >
> > CREATE TABLE pru (g1 geometry, g2 geometry);
> > ALTER TABLE public.pru OWNER TO postgres;
> > INSERT INTO pru (g1, g2) VALUES
> > ('0105000000010000000102000000020000009A9999591B0D54413D0AD763BAF15641000000502C0D5441D7A3705DC5F15641',
> > '010500000001000000010200000005000000000000502C0D5441D7A3705DC5F15641EC51B80E420D54411F85EBC1A3F156418FC2F518310D544185EB51C898F156419A9999591B0D54413D0AD763BAF15641000000502C0D5441D7A3705DC5F15641');
> >
> > I dropped the table made with the SELECT command described above and
> > re-created the table running this script.
> > And the I run:
> >
> > select astext(g1),astext(g2),
> > within(geometryfromtext(astext(g1)),geometryfromtext(astext(g2)))as w1,
> > within(g1,g2) as w2
> > from pru
> >
> > again and I got
> >
> > --"MULTILINESTRING((5256301.4 6014697.56,5256369.25
> > 6014741.46))";"MULTILINESTRING((5256369.25 6014741.46,5256456.23
> > 6014607.03,5256388.39 6014563.13,5256301.4 6014697.56,5256369.25
> > 6014741.46))";t;t
> >
> > with both withins returning TRUE !!!!!
> >
> > I'm really LOST!
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