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Thread: How to dereference 2 dimensional array?

How to dereference 2 dimensional array?

From
ChoonSoo Park
Date:

I would like to construct hstore array from 2 dimensional array.


For example, 


'{{f1, 1, f2, 123, f3, ABC, ...}, {f1, 2, f2, 345, f3, DEF, ...}}'


Should be converted to


2 hstore values

"f1"=>"1", "f2"=>"123", "f3"=>"ABC", ...

"f2"=>"2", "f2"=>"345", "f3"=>"DEF", ...


create or replace function convertHStore(p1 text[][]) RETURNS hstore[]


hstore function requires text[] to convert array to hstore. Therefore I should be able to dereference 2 dimensional array element.

Inside this custom plpgsql function, p1[1] is not valid syntax to dereference the 1st element in p1.


Anyone knows how to solve this problem?


Thank you,

Choon Park 

Re: How to dereference 2 dimensional array?

From
Bartosz Dmytrak
Date:
Hi,
this could be start point for discussion:


CREATE OR REPLACE FUNCTION public."arraysToHstore" (IN a TEXT[], OUT c hstore[])
RETURNS hstore[]
AS
$BODY$
DECLARE 
i INT;
elements INT;
dim INT;
BEGIN
elements := array_length(a,2); -- # of elements in each dimension
dim := array_length(a,1); -- # of dimensions
a := string_to_array(array_to_string(a, '|', 'NULL'), '|', 'NULL'); --rewrite multidimensional array into single dimensional

FOR i IN 0..(dim -1) LOOP --loop throug all dimensions to create hsore array (0 is for first elment in rewrited array)
c[i+1] = hstore (a[(i*elements)+1: (i+1)*elements]); --create hstore array element using part of array "a", this part (window) is moving while loop is evaluated)
END LOOP;

END
$BODY$
LANGUAGE plpgsql SECURITY DEFINER IMMUTABLE STRICT;

--usage example
SELECT (public."arraysToHstore"('{{"f1", "1", "f3", "123", "f4", "ABC"}, {"f5", "2", "f6", "345", "f7", "DEF"}}')::hstore[])[2]

This works for me (PostgreSQL 9.1.2).
You can pass whatever text array You want (any size, but 2 dimensions only) and You will receive 1 dimentional hstore array with number of elements corresponding to input array's dimensions)

Regards,
Bartek


2012/2/16 ChoonSoo Park <luispark@gmail.com>

I would like to construct hstore array from 2 dimensional array.


For example, 


'{{f1, 1, f2, 123, f3, ABC, ...}, {f1, 2, f2, 345, f3, DEF, ...}}'


Should be converted to


2 hstore values

"f1"=>"1", "f2"=>"123", "f3"=>"ABC", ...

"f2"=>"2", "f2"=>"345", "f3"=>"DEF", ...


create or replace function convertHStore(p1 text[][]) RETURNS hstore[]


hstore function requires text[] to convert array to hstore. Therefore I should be able to dereference 2 dimensional array element.

Inside this custom plpgsql function, p1[1] is not valid syntax to dereference the 1st element in p1.


Anyone knows how to solve this problem?


Thank you,

Choon Park 


Re: How to dereference 2 dimensional array?

From
Merlin Moncure
Date:
On Thu, Feb 16, 2012 at 9:48 AM, ChoonSoo Park <luispark@gmail.com> wrote:
> I would like to construct hstore array from 2 dimensional array.
>
>
> For example,
>
>
> '{{f1, 1, f2, 123, f3, ABC, ...}, {f1, 2, f2, 345, f3, DEF, ...}}'
>
>
> Should be converted to
>
>
> 2 hstore values
>
> "f1"=>"1", "f2"=>"123", "f3"=>"ABC", ...
>
> "f2"=>"2", "f2"=>"345", "f3"=>"DEF", ...
>
>
> create or replace function convertHStore(p1 text[][]) RETURNS hstore[]
>
>
> hstore function requires text[] to convert array to hstore. Therefore I
> should be able to dereference 2 dimensional array element.
>
> Inside this custom plpgsql function, p1[1] is not valid syntax to
> dereference the 1st element in p1.
>
>
> Anyone knows how to solve this problem?

This is a good use of the 9.1 SLICE feature:

CREATE FUNCTION slice_hstore(text[]) RETURNS SETOF hstore AS $$
DECLARE
  x text[];
BEGIN
  FOREACH x SLICE 1 IN ARRAY $1
  LOOP
    return next hstore(x);
  END LOOP;
END;
$$ LANGUAGE plpgsql;

select slice_hstore('{{g1, 1, f2, 123, f3, ABC}, {f1, 2, f2, 345, f3,
DEF}}'::text[]);

postgres=# select slice_hstore('{{g1, 1, f2, 123, f3, ABC}, {f1, 2,
f2, 345, f3, DEF}}'::text[]);
            slice_hstore
-------------------------------------
 "f2"=>"123", "f3"=>"ABC", "g1"=>"1"
 "f1"=>"2", "f2"=>"345", "f3"=>"DEF"
(2 rows)

postgres=# select array(select slice_hstore('{{g1, 1, f2, 123, f3,
ABC}, {f1, 2, f2, 345, f3, DEF}}'::text[]));
                                               ?column?
-------------------------------------------------------------------------------------------------------
 {"\"f2\"=>\"123\", \"f3\"=>\"ABC\", \"g1\"=>\"1\"","\"f1\"=>\"2\",
\"f2\"=>\"345\", \"f3\"=>\"DEF\""}
(1 row)


merlin