[postgis-users] Is that possible a function to behave differently inside and outside another main function code?
rodrigosperb
rodrigosperb at gmail.com
Thu Nov 12 07:06:18 PST 2009
Hello Kevin,
Yes, I know a DISTINCT FOLLOWING a UNION ALL would be the same as UNION, but
I just wanted to try out in case of some sort of bug.
Well, I'm quite sure that the input have at least 2 points. Because they are
"bigger" functions (implemented as LINESTRING) that I cut a part (and my
RAISE NOTICEs during the code seem to indicate that this cutting performs
correctly), so they will have at least 2-points, start and end of the X
interval in which I cut the function to give as input.
I really cannot understand what goes wrong, I'm affraid.
Rodrigo Sperb
Kevin Neufeld wrote:
>
> A DISTINCT and a UNION ALL will yield the same results as a straight up
> UNION. I didn't realize that you need to have duplicates removed.
>
> In that case, my guess is that the issue is with your input data.
> You're selecting ST_X from $1, ST_X from $2 and ST_MaxX from $1. Have
> you verified that this always yields at least two distinct X values with
> your data? Try replacing the first SELECT clause with a simple "SELECT
> xy.t" and add a "GROUP BY xy.t HAVING count(*) < 2" at the end to
> identify all erroneous input data values.
>
> Cheers,
> Kevin
>
> Rodrigo Sperb wrote:
>> Hello,
>>
>> Following what Kevin said about UNION ALL, I have tried to change the
>> code (below) using UNION ALL and then SELECT DISTINCT (as I need the
>> same X may be in both functions and I don't want a replicate. But I
>> still ge the same error (eventual single-point Linestring that should
>> never happen. Here is the code (so that I don't need to look-up the
>> previous message:
>>
>> ...header...
>> SELECT st_LineFromMultiPoint(st_Collect(st_MakePoint(xy.t,xy.at
>> <http://xy.at/>)))
>>
>> FROM (SELECT q.t, dr_delay_value($1,q.t) +
>> dr_delay_value($3,dr_delay_value($1,q.t)) AS at
>>
>> --- dr_delay_value is a simple look-up function for a certain X
>> value....
>> FROM (SELECT st_X(st_PointN($1,n)) AS t
>> FROM generate_series(1,st_NumPoints($1)) AS h(n)
>> UNION
>> SELECT st_X(st_PointN($2,n)) AS t
>> FROM generate_series(1,st_NumPoints($2)) AS h(n)
>> UNION
>> SELECT st_Xmax($1) AS t
>> ) AS q ORDER BY q.t) AS xy
>> ...bottom...
>>
>>
>> I then changed it to:
>>
>> SELECT st_LineFromMultiPoint(st_Collect(st_MakePoint(xy.t,xy.at
>> <http://xy.at/>)))
>>
>> FROM (SELECT DISTINCT q.t, dr_delay_value($1,q.t) +
>> dr_delay_value($3,dr_delay_value($1,q.t)) AS at
>>
>> --- dr_delay_value is a simple look-up function for a certain X
>> value....
>> FROM (SELECT st_X(st_PointN($1,n)) AS t
>> FROM generate_series(1,st_NumPoints($1)) AS h(n)
>> UNION ALL
>> SELECT st_X(st_PointN($2,n)) AS t
>> FROM generate_series(1,st_NumPoints($2)) AS h(n)
>> UNION
>> SELECT st_Xmax($1) AS t
>> ) AS q ORDER BY q.t) AS xy
>> ...bottom...
>>
>>
>> And I know what went inside when I got the error was:
>>
>> Inputs of function:
>> $1 = LINESTRING(28800 28809.0366506299,28826.9908145614 28836.029580065)
>> $2 = LINESTRING(28800 45.4281818181818,28826.9908145614 45.4299607582325)
>> $3 = LINESTRING(0 43.53,52800 47.01,62700 74.87,86400 43.53) - edge
>> delay function
>>
>> Output:
>> result =
>> LINESTRING(28800 28854.4654280455) - thus is missing a pair
>> X=28826.9908145614, Y = 28836.029580065 + Y of $3 for 28836.029580065
>>
>> But here is what I find most intriguing: if I simulate the inputs
>> above outside of the main function (in which this one that is
>> returning an eventual error runs), it simply works.
>>
>> SELECT
>> st_AsText(dr_sum_arrivaltime_edgedelay(st_GeometryFromText('LINESTRING(28800
>> 28809.0366506299,28826.9908145614 28836.029580065)'),
>>
>> st_GeometryFromText('LINESTRING(28800
>> 45.4281818181818,28826.9908145614 45.4299607582325)'),
>> st_GeometryFromText('LINESTRING(0
>> 43.53,52800 47.01,62700 74.87,86400 43.53)')))
>>
>> = "LINESTRING(28800 28854.4654280455,28826.9908145614 28881.46013656)"
>>
>> I hope anyone can give me a clue on that one. It's sort of really
>> bothering already, as I can't imagine why that happens...
>>
>> Best regards,
>>
>> Rodrigo Sperb
>>
>>
>>
>>
>>
>> ------------------------------
>>
>> Message: 7
>> Date: Sun, 08 Nov 2009 09:25:37 -0800
>> From: Kevin Neufeld <kneufeld at refractions.net
>> <mailto:kneufeld at refractions.net>>
>> Subject: Re: [postgis-users] Is that possible a function to behave
>> differently inside and outside another main function code?
>> To: PostGIS Users Discussion
>> <postgis-users at postgis.refractions.net
>> <mailto:postgis-users at postgis.refractions.net>>
>> Message-ID: <4AF6FF11.3080607 at refractions.net
>> <mailto:4AF6FF11.3080607 at refractions.net>>
>> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>>
>> Are you sure you want to use "UNION" and not "UNION ALL"? The former
>> will remove duplicates, the latter does not. It's conceivable
>> that when
>> UNIONed, the three SELECT st_X clauses will return a single value.
>> Collected and put through ST_LineFromMultiPoint would probably
>> result in
>> a single point line (depending on which version of PostGIS you are
>> using
>> - the newer versions will ERROR with "geometry requires more
>> points").
>>
>> Hope that helps,
>> Kevin
>>
>> rodrigosperb wrote:
>> > Hello,
>> >
>> > I have a bit of a problem that is sort of driving me crazy. I
>> need to
>> > perform an "addition of two (mathematical) functions". I
>> represent them as
>> > linestrings in my solution, and it is part of another bigger
>> function. The
>> > code is as follows:
>> >
>> > ...header...
>> > SELECT st_LineFromMultiPoint(st_Collect(st_MakePoint(xy.t,xy.at
>> <http://xy.at>)))
>> > FROM (SELECT q.t, dr_delay_value($1,q.t) +
>> > dr_delay_value($3,dr_delay_value($1,q.t)) AS at
>> > FROM (SELECT st_X(st_PointN($1,n)) AS t
>> > FROM generate_series(1,st_NumPoints($1)) AS h(n)
>> > UNION
>> > SELECT st_X(st_PointN($2,n)) AS t
>> > FROM generate_series(1,st_NumPoints($2)) AS h(n)
>> > UNION
>> > SELECT st_Xmax($1) AS t
>> > ) AS q ORDER BY q.t) AS xy
>> > ...bottom...
>> > dr_delay_value() is simply a look-up function that takes the Y
>> value for a
>> > certain X.
>> >
>> > The thing is that eventually this fuction is failing on
>> returning more
>> > specifically a 2-points linestring (that sould) and returns only
>> a single
>> > point one. Now, I have prepared a "wrapper" PL/Pgsql function to
>> keep track
>> > of what is passed to that function (perhaps that was the reason
>> for the
>> > error. With that I'm pretty much sure that the arguments passed
>> are fine,
>> > and still get the same error... Strangely, with my wrapper
>> function keeping
>> > track of the arguments passed to the function I was able to try
>> out to run
>> > the same request (that inside of the bigger function fails)
>> separately, and
>> > guess what? is simply works!!
>> >
>> > I hope anyone may have a clue of what is going on. That's a very
>> strange
>> > behavior, I would say.
>> >
>> > Regards,
>> >
>> > Rodrigo Sperb
>> >
>>
>>
>> ------------------------------
>>
>> Message: 8
>> Date: Sun, 8 Nov 2009 09:26:41 -0800 (PST)
>> From: rodrigosperb <rodrigosperb at gmail.com
>> <mailto:rodrigosperb at gmail.com>>
>> Subject: Re: [postgis-users] Is that possible a function to behave
>> differently inside and outside another main function code?
>> To: postgis-users at postgis.refractions.net
>> <mailto:postgis-users at postgis.refractions.net>
>> Message-ID: <26255804.post at talk.nabble.com
>> <mailto:26255804.post at talk.nabble.com>>
>> Content-Type: text/plain; charset=us-ascii
>>
>>
>> Hi Kevin,
>>
>> Thanks for your repply. I can't be sure whether the two functions
>> have the
>> same X value, and I don't want them twice, that's why I was using
>> UNION,
>> instead of UNION ALL (which is much faster even...).
>>
>> But what you said make some sense. Do you think if use first a
>> UNION ALL and
>> then in the outer query (when I order by q.t) I use DISTINCT may
>> work?
>>
>> I think I will try it out.
>>
>> Thanks again for the help.
>>
>> Rodrigo Sperb
>>
>>
>>
>> Kevin Neufeld wrote:
>> >
>> > Are you sure you want to use "UNION" and not "UNION ALL"? The
>> former
>> > will remove duplicates, the latter does not. It's conceivable
>> that when
>> > UNIONed, the three SELECT st_X clauses will return a single value.
>> > Collected and put through ST_LineFromMultiPoint would probably
>> result in
>> > a single point line (depending on which version of PostGIS you
>> are using
>> > - the newer versions will ERROR with "geometry requires more
>> points").
>> >
>> > Hope that helps,
>> > Kevin
>> >
>> > rodrigosperb wrote:
>> >> Hello,
>> >>
>> >> I have a bit of a problem that is sort of driving me crazy. I
>> need to
>> >> perform an "addition of two (mathematical) functions". I
>> represent them
>> >> as
>> >> linestrings in my solution, and it is part of another bigger
>> function.
>> >> The
>> >> code is as follows:
>> >>
>> >> ...header...
>> >> SELECT st_LineFromMultiPoint(st_Collect(st_MakePoint(xy.t,xy.at
>> <http://xy.at>)))
>> >> FROM (SELECT q.t, dr_delay_value($1,q.t) +
>> >> dr_delay_value($3,dr_delay_value($1,q.t)) AS at
>> >> FROM (SELECT st_X(st_PointN($1,n)) AS t
>> >> FROM generate_series(1,st_NumPoints($1)) AS h(n)
>> >> UNION
>> >> SELECT st_X(st_PointN($2,n)) AS t
>> >> FROM generate_series(1,st_NumPoints($2)) AS h(n)
>> >> UNION
>> >> SELECT st_Xmax($1) AS t
>> >> ) AS q ORDER BY q.t) AS xy
>> >> ...bottom...
>> >> dr_delay_value() is simply a look-up function that takes the Y
>> value for
>> >> a
>> >> certain X.
>> >>
>> >> The thing is that eventually this fuction is failing on
>> returning more
>> >> specifically a 2-points linestring (that sould) and returns
>> only a single
>> >> point one. Now, I have prepared a "wrapper" PL/Pgsql function
>> to keep
>> >> track
>> >> of what is passed to that function (perhaps that was the reason
>> for the
>> >> error. With that I'm pretty much sure that the arguments passed
>> are fine,
>> >> and still get the same error... Strangely, with my wrapper
>> function
>> >> keeping
>> >> track of the arguments passed to the function I was able to try
>> out to
>> >> run
>> >> the same request (that inside of the bigger function fails)
>> separately,
>> >> and
>> >> guess what? is simply works!!
>> >>
>> >> I hope anyone may have a clue of what is going on. That's a
>> very strange
>> >> behavior, I would say.
>> >>
>> >> Regards,
>> >>
>> >> Rodrigo Sperb
>> >>
>> > _______________________________________________
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>> > http://postgis.refractions.net/mailman/listinfo/postgis-users
>> >
>> >
>>
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>>
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