Subject: Re: Alternate methods for multiple rows input/output to a function.
To: RAJIN RAJ K <rajin89@gmail.com>
References: 
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Cc: pgsql-general <pgsql-general@postgresql.org>
From: Adrian Klaver <adrian.klaver@aklaver.com>
Message-ID: <6e492dc3-c1dd-2a97-643d-411cc0655fd6@aklaver.com>
Date: Tue, 28 May 2019 10:26:41 -0700
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On 5/28/19 8:06 AM, RAJIN RAJ K wrote:

Please reply to list also.
Ccing list.

> Thanks for the response.
> 
> CTE is not useful in my case. Here i want to pass the table to a 
> function and get the filtered results back from the function.
> I tried few but not use full.
> 1. Pass table input --> Ref cursor is the only option but which again 
> require loop to fetch the records. (FETCH ALL results cannot be stored 
> in a variable)
>      Here im creating temp table withe required input data before the 
> function call.

I'm going to take a stab at this though I do not entirely follow the 
logic. Definitely not tested:

1) create function filter_id(tbl_name varchar)
return table (id bigint)
begin

--> Assuming input table is already created #temp_input_id

return query EXECUTE format('select id '
'from tbl a '
'inner join'
'%I b on (a.id = b.id)'
'where a.<conditions>', tbl_name);

end;

2) In calling function:

WITH temp_tbl AS (select id from tbla...
), filter_tbl AS (select * from filter_id(temp_bl))
select a.*
from tb3 a inner join tb4 inner join tb 5 inner join filter_tbl;


> 
> 
> On Tue, May 28, 2019 at 8:29 PM Adrian Klaver <adrian.klaver@aklaver.com 
> <mailto:adrian.klaver@aklaver.com>> wrote:
> 
>     On 5/28/19 7:36 AM, RAJIN RAJ K wrote:
>      > --> Function ' filter_id ' filters the ID's based on some conditions.
>      > --> Input is set of ID's. (Not directly taking the input since
>     there is
>      > no provision to pass multiple rows to a function)
> 
>     To be honest I cannot follow what you are trying to achieve below. I do
>     have one suggestion as to creating temp tables.
> 
>     Why not use a  CTE:
> 
>     https://www.postgresql.org/docs/11/queries-with.html
> 
>     in the function to build a 'temp' table on the fly?
> 
>      >
>      > create function filter_id()
>      > return table (id bigint)
>      > begin
>      >
>      > --> Assuming input table is already created #temp_input_id
>      >
>      > retun query as select id
>      > from tbl a
>      > inner join
>      > #temp_input_id b on (a.id <http://a.id> <http://a.id> = b.id
>     <http://b.id> <http://b.id>)
>      > where a.<conditions>;
>      >
>      > end;
>      >
>      >
>      > --> Calling Function:
>      >
>      > create function caller()
>      > return table (id bigint,col1 bigint, col2 bigint)
>      > begin
>      >
>      > --> do some processing
>      >
>      > --> Find out the input id's for filtering.
>      >
>      > --> Create temp table for providing input for the filtering function
>      >
>      > create temp table #TEMP1
>      > as select id from tbla........;
>      > (Cannot move the input id logic to  filter_function)
>      >
>      > --> calling the filter function
>      > create temp table #TEMP2
>      > as select * from filter_id(); --> This is a generic function used in
>      > many functions.
>      >
>      >
>      > return query
>      > as select a.*
>      > from tb3 a inner join tb4 inner join tb 5 inner join #TEMP2;
>      > end;
>      >
>      >
>      > Is there any alternate way of achieving this? Passing multiple
>     records
>      > to a function im creating a temp table before invoking the function.
>      > For receiving an output of multiple rows i'm creating a temp
>     table to
>      > reuse further in the code.
>      >
>      > Can this be done using Refcursor? Is it possible to convert
>     refcursor to
>      > a temp table and use it as normal  table in query?
>      >
>      >
> 
> 
>     -- 
>     Adrian Klaver
>     adrian.klaver@aklaver.com <mailto:adrian.klaver@aklaver.com>
> 


-- 
Adrian Klaver
adrian.klaver@aklaver.com