Thread: How to count the number of items in an Array?

How to count the number of items in an Array?

From
Andre Lopes
Date:
Hi,
 
I have googled, but I can't find how to count the number of items in an Array in Plpgsql.
 
Someone can give me a clue on that?
 
 
Best Regads,
 

Re: How to count the number of items in an Array?

From
Andreas Kretschmer
Date:
Andre Lopes <lopes80andre@gmail.com> wrote:

> Hi,
>
> I have googled, but I can't find how to count the number of items in an Array
> in Plpgsql.
>
> Someone can give me a clue on that?

Sure, you can use array_upper() - array_lower():

Zeit: 0,205 ms
test=*# select array_upper(array[1,2,3],1) - array_lower(array[1,2,3],1);
 ?column?
----------
        2
(1 Zeile)


or:

test=*# select array_upper(array[1,2,3],1) - array_lower(array[1,2,3],1) + 1;
 ?column?
----------
        3
(1 Zeile)


Or, if your array starts with the first element, simple:

test=*# select array_upper(array[1,2,3,NULL,5],1);
 array_upper
-------------
           5
(1 Zeile)



Andreas
--
Really, I'm not out to destroy Microsoft. That will just be a completely
unintentional side effect.                              (Linus Torvalds)
"If I was god, I would recompile penguin with --enable-fly."   (unknown)
Kaufbach, Saxony, Germany, Europe.              N 51.05082°, E 13.56889°

Re: How to count the number of items in an Array?

From
Andre Lopes
Date:
Hi,
 
Thanks for the reply.
 
My problem is that I can't have the array with all items. I need to read from a table and store in an Array the values.
 
I have this:
 
[code]
CREATE OR REPLACE FUNCTION "public"."apr_update_newsletter_distritos" ("pEMAIL" varchar, "pID_WEBSITE_RECOLHA" varchar) RETURNS void AS
$body$
DECLARE
    pEMAIL       alias for $1; -- vai ser preciso
    pID_WEBSITE_RECOLHA   alias for $2; -- vai ser preciso
    vDISTRITOS_NA_TABELA  varchar[];
    vDISTRITOS_NA_TABELA_CONST varchar[];
    vd integer;
    vas varchar;
BEGIN
 -- ### Vou gravar num array os registos da chave em q se vai mexer
    -- vou entao passar os registos para o array vDISTRITOS_NA_TABELA
    FOR vDISTRITOS_NA_TABELA IN
    SELECT array[id_distrito] FROM am_newsletter_distritos
    WHERE email = pEMAIL and id_website_recolha = pID_WEBSITE_RECOLHA   
  LOOP
    RAISE NOTICE 'value: %', vDISTRITOS_NA_TABELA;
    END LOOP;
   
    -- array 2 string
    select array_to_string(vDISTRITOS_NA_TABELA, ',') into vas;
 RAISE NOTICE 'string with items of array: %', vas;
   
    -- Vou contar o número dos registos do array
    -- select array_upper(vDISTRITOS_NA_TABELA, 1) into vd;
    -- RAISE NOTICE 'num array: %', vd;
END;
$body$
LANGUAGE 'plpgsql' VOLATILE CALLED ON NULL INPUT SECURITY INVOKER;
[/code]
This select returns me 4 values:
[code]
    SELECT array[id_distrito] FROM am_newsletter_distritos
    WHERE email = pEMAIL and id_website_recolha = pID_WEBSITE_RECOLHA   
[/code]
 
The values are '11, 12,16, 16'. I haven't found a way to store this as an array to the variable vDISTRITOS_NA_TABELA. Someone can give me a clue on how to do that?
 
Best Regards,

 
On Sun, Feb 21, 2010 at 8:38 AM, Andreas Kretschmer <akretschmer@spamfence.net> wrote:
Andre Lopes <lopes80andre@gmail.com> wrote:

> Hi,
>
> I have googled, but I can't find how to count the number of items in an Array
> in Plpgsql.
>
> Someone can give me a clue on that?

Sure, you can use array_upper() - array_lower():

Zeit: 0,205 ms
test=*# select array_upper(array[1,2,3],1) - array_lower(array[1,2,3],1);
 ?column?
----------
       2
(1 Zeile)


or:

test=*# select array_upper(array[1,2,3],1) - array_lower(array[1,2,3],1) + 1;
 ?column?
----------
       3
(1 Zeile)


Or, if your array starts with the first element, simple:

test=*# select array_upper(array[1,2,3,NULL,5],1);
 array_upper
-------------
          5
(1 Zeile)



Andreas
--
Really, I'm not out to destroy Microsoft. That will just be a completely
unintentional side effect.                              (Linus Torvalds)
"If I was god, I would recompile penguin with --enable-fly."   (unknown)
Kaufbach, Saxony, Germany, Europe.              N 51.05082°, E 13.56889°

--
Sent via pgsql-general mailing list (pgsql-general@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-general

Re: How to count the number of items in an Array?

From
Andreas Kretschmer
Date:
Andre Lopes <lopes80andre@gmail.com> wrote:

> Hi,
>
> Thanks for the reply.
>
> My problem is that I can't have the array with all items. I need to read from a
> table and store in an Array the values.

Not sure if i understand you, but how about:

test=*# select * from foo;
 a
---
 1
 3
 5
 7
(4 Zeilen)

Zeit: 0,203 ms
test=*# select array_agg(a) from foo;
 array_agg
-----------
 {1,3,5,7}
(1 Zeile)


The function returns a column as an array.



Andreas
--
Really, I'm not out to destroy Microsoft. That will just be a completely
unintentional side effect.                              (Linus Torvalds)
"If I was god, I would recompile penguin with --enable-fly."   (unknown)
Kaufbach, Saxony, Germany, Europe.              N 51.05082°, E 13.56889°

Re: How to count the number of items in an Array?

From
Andre Lopes
Date:
One more time, thanks for the reply. I'am using postgre 8.3. I think I don't have the array_agg(), there is another way of doing it?
 
Best Regards,


 
On Sun, Feb 21, 2010 at 2:46 PM, Andreas Kretschmer <akretschmer@spamfence.net> wrote:
Andre Lopes <lopes80andre@gmail.com> wrote:

> Hi,
>
> Thanks for the reply.
>
> My problem is that I can't have the array with all items. I need to read from a
> table and store in an Array the values.

Not sure if i understand you, but how about:

test=*# select * from foo;
 a
---
 1
 3
 5
 7
(4 Zeilen)

Zeit: 0,203 ms
test=*# select array_agg(a) from foo;
 array_agg
-----------
 {1,3,5,7}
(1 Zeile)


The function returns a column as an array.



Andreas
--
Really, I'm not out to destroy Microsoft. That will just be a completely
unintentional side effect.                              (Linus Torvalds)
"If I was god, I would recompile penguin with --enable-fly."   (unknown)
Kaufbach, Saxony, Germany, Europe.              N 51.05082°, E 13.56889°

--
Sent via pgsql-general mailing list (pgsql-general@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-general

Re: How to count the number of items in an Array?

From
Andreas Kretschmer
Date:
Andre Lopes <lopes80andre@gmail.com> wrote:

> One more time, thanks for the reply. I'am using postgre 8.3. I think I don't
> have the array_agg(), there is another way of doing it?

Sure.

The doc contains an example for a user-defined aggregate-function:
http://www.postgresql.org/docs/8.4/interactive/xaggr.html

It works with versions prior 8.4.


test=*# CREATE AGGREGATE array_accum (anyelement)
test-# (
test(#     sfunc = array_append,
test(#     stype = anyarray,
test(#     initcond = '{}'
test(# );
CREATE AGGREGATE
Zeit: 44,645 ms
test=*# select array_accum(a) from foo;
 array_accum
-------------
 {1,3,5,7}
(1 Zeile)



Andreas
--
Really, I'm not out to destroy Microsoft. That will just be a completely
unintentional side effect.                              (Linus Torvalds)
"If I was god, I would recompile penguin with --enable-fly."   (unknown)
Kaufbach, Saxony, Germany, Europe.              N 51.05082°, E 13.56889°

Re: How to count the number of items in an Array?

From
Andre Lopes
Date:
Hi,
 
Thanks for the reply.
 
I have done it in this way:
 
[code]
    FOR vDISTRITOS_NA_TABELA IN
     SELECT array[id_distrito] FROM am_newsletter_distritos
     WHERE email = pEMAIL and id_website_recolha = pID_WEBSITE_RECOLHA   
  LOOP
     vDISTRITOS_NA_TABELA_CONST := vDISTRITOS_NA_TABELA_CONST || vDISTRITOS_NA_TABELA;
    END LOOP;
[/code]
 
Best Regards,


 
On Sun, Feb 21, 2010 at 3:25 PM, Andreas Kretschmer <akretschmer@spamfence.net> wrote:
Andre Lopes <lopes80andre@gmail.com> wrote:

> One more time, thanks for the reply. I'am using postgre 8.3. I think I don't
> have the array_agg(), there is another way of doing it?

Sure.

The doc contains an example for a user-defined aggregate-function:
http://www.postgresql.org/docs/8.4/interactive/xaggr.html

It works with versions prior 8.4.


test=*# CREATE AGGREGATE array_accum (anyelement)
test-# (
test(#     sfunc = array_append,
test(#     stype = anyarray,
test(#     initcond = '{}'
test(# );
CREATE AGGREGATE
Zeit: 44,645 ms
test=*# select array_accum(a) from foo;
 array_accum
-------------
 {1,3,5,7}
(1 Zeile)



Andreas
--
Really, I'm not out to destroy Microsoft. That will just be a completely
unintentional side effect.                              (Linus Torvalds)
"If I was god, I would recompile penguin with --enable-fly."   (unknown)
Kaufbach, Saxony, Germany, Europe.              N 51.05082°, E 13.56889°

--
Sent via pgsql-general mailing list (pgsql-general@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-general