plpgsql function with more than one array argument
Hi,
thanks for reading this message.
I have a table (in a postgres database) looking like this:
Table "zdec_bhab"
Attribute | Type | Modifier
-----------+-----------+----------
run | bigint |
evt | bigint |
...
pcha | real[] |
...
where pcha is a 2D array, i.e. the first index can go from 1 to some
number and the second is 1..3.
Now, I'd like to create a plpgsql function taking as an argument
two vectors (arrays) from pcha:
CREATE FUNCTION mytest(real[],real[]) RETURNS real AS '
DECLARE
p1 ALIAS FOR $1;
p2 ALIAS FOR $2;
begin
-- RAISE NOTICE ''xxx %'',p2;
return p2[1][1];
end;' LANGUAGE 'plpgsql';
I do the following query:
select
pcha[1:1][1:3],pcha[2:2][1:3],mytest(pcha[1:1][1:3],pcha[2:2][1:3]) from
zdec_bhab where nch>=2;
which yields:
pcha |
pcha | mytest
---------------------------------------------+---------------------------------------------+--------
{{"-21.0788","35.0317","19.2111"}} |
{{"21.0605","-34.995","-19.2111"}} |
i.e. mytest seems to return something empty... however, If I uncomment
the RAISE NOTICE
line, I see the correct values (as in the output of the select
statement).
If I do
select
pcha[1:1][1:3],pcha[2:2][1:3],mytest(pcha[2:2][1:3],pcha[1:1][1:3]) from
zdec_bhab where nch>=2;
(i.e. the arguments of mytest exchanged), I get the correct values.
Am I doing something wrong or is this a 'feature' ?
(I'm using PostgreSQL 7.1.3 on i686-pc-linux-gnu, compiled by GCC
2.95.3).
Is it possible in plpgsql to have functions with more than
one array argument ? What about plperl ?
Or do I have to convert the 2D array into three 1D arrays pcha_x, pcha_y
and pcha_z ?
best regards & thanks for the help,
Andr�
Andre Holzner <Andre.Holzner@cern.ch> writes:
Am I doing something wrong or is this a 'feature' ?
What's biting you is that the array slice operator uses the provided
lower bounds in the resultant array. For example:
regression=# select pcha from zdec_bhab;
pcha
------------------------------------
{{11,12,13},{21,22,23},{31,32,33}}
(1 row)
regression=# select array_dims(pcha) from zdec_bhab;
array_dims
------------
[1:3][1:3]
(1 row)
regression=# select pcha[2:2][1:3] from zdec_bhab;
pcha
--------------
{{21,22,23}}
(1 row)
regression=# select array_dims(pcha[2:2][1:3]) from zdec_bhab;
array_dims
------------
[2:2][1:3]
(1 row)
So your function receives an array with first index starting at 2,
which it's not expecting; its attempt to fetch element [1][1] is out
of bounds and produces a NULL.
Offhand this behavior seems like a misfeature: perhaps it'd be more
sensible for the extracted slice to always have index lower bounds
set to 1. But I'd like to see some discussion before changing it
(and I don't plan to touch it before 7.2 release, in any case ;-)).
Comments anyone?
regards, tom lane
Is this a TODO item?
---------------------------------------------------------------------------
Tom Lane wrote:
Andre Holzner <Andre.Holzner@cern.ch> writes:
Am I doing something wrong or is this a 'feature' ?
What's biting you is that the array slice operator uses the provided
lower bounds in the resultant array. For example:regression=# select pcha from zdec_bhab;
pcha
------------------------------------
{{11,12,13},{21,22,23},{31,32,33}}
(1 row)regression=# select array_dims(pcha) from zdec_bhab;
array_dims
------------
[1:3][1:3]
(1 row)regression=# select pcha[2:2][1:3] from zdec_bhab;
pcha
--------------
{{21,22,23}}
(1 row)regression=# select array_dims(pcha[2:2][1:3]) from zdec_bhab;
array_dims
------------
[2:2][1:3]
(1 row)So your function receives an array with first index starting at 2,
which it's not expecting; its attempt to fetch element [1][1] is out
of bounds and produces a NULL.Offhand this behavior seems like a misfeature: perhaps it'd be more
sensible for the extracted slice to always have index lower bounds
set to 1. But I'd like to see some discussion before changing it
(and I don't plan to touch it before 7.2 release, in any case ;-)).Comments anyone?
regards, tom lane
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--
Bruce Momjian | http://candle.pha.pa.us
pgman@candle.pha.pa.us | (610) 853-3000
+ If your life is a hard drive, | 830 Blythe Avenue
+ Christ can be your backup. | Drexel Hill, Pennsylvania 19026Bruce Momjian <pgman@candle.pha.pa.us> writes:
Is this a TODO item?
I guess so, since no one seems to have objected to the proposed change.
It's a pretty trivial change; I'll take care of it.
regards, tom lane
Show quoted text
Tom Lane wrote:
Andre Holzner <Andre.Holzner@cern.ch> writes:
Am I doing something wrong or is this a 'feature' ?
What's biting you is that the array slice operator uses the provided
lower bounds in the resultant array. For example:regression=# select pcha from zdec_bhab;
pcha
------------------------------------
{{11,12,13},{21,22,23},{31,32,33}}
(1 row)regression=# select array_dims(pcha) from zdec_bhab;
array_dims
------------
[1:3][1:3]
(1 row)regression=# select pcha[2:2][1:3] from zdec_bhab;
pcha
--------------
{{21,22,23}}
(1 row)regression=# select array_dims(pcha[2:2][1:3]) from zdec_bhab;
array_dims
------------
[2:2][1:3]
(1 row)So your function receives an array with first index starting at 2,
which it's not expecting; its attempt to fetch element [1][1] is out
of bounds and produces a NULL.Offhand this behavior seems like a misfeature: perhaps it'd be more
sensible for the extracted slice to always have index lower bounds
set to 1. But I'd like to see some discussion before changing it
(and I don't plan to touch it before 7.2 release, in any case ;-)).Comments anyone?
regards, tom lane
Hello developpers,
Tom Lane wrote:
Bruce Momjian <pgman@candle.pha.pa.us> writes:
Is this a TODO item?
I guess so, since no one seems to have objected to the proposed change.
It's a pretty trivial change; I'll take care of it.regards, tom lane
I learned to live without it, but I wont be the last one
who tries to use such queries.
best regards & thanks a lot for your efforts,
André
Tom Lane wrote:
Andre Holzner <Andre.Holzner@cern.ch> writes:
Am I doing something wrong or is this a 'feature' ?
What's biting you is that the array slice operator uses the provided
lower bounds in the resultant array. For example:regression=# select pcha from zdec_bhab;
pcha
------------------------------------
{{11,12,13},{21,22,23},{31,32,33}}
(1 row)regression=# select array_dims(pcha) from zdec_bhab;
array_dims
------------
[1:3][1:3]
(1 row)regression=# select pcha[2:2][1:3] from zdec_bhab;
pcha
--------------
{{21,22,23}}
(1 row)regression=# select array_dims(pcha[2:2][1:3]) from zdec_bhab;
array_dims
------------
[2:2][1:3]
(1 row)So your function receives an array with first index starting at 2,
which it's not expecting; its attempt to fetch element [1][1] is out
of bounds and produces a NULL.Offhand this behavior seems like a misfeature: perhaps it'd be more
sensible for the extracted slice to always have index lower bounds
set to 1. But I'd like to see some discussion before changing it
(and I don't plan to touch it before 7.2 release, in any case ;-)).Comments anyone?
regards, tom lane
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