Re: record from plpgsql function performance

Thanks, David.
Works perfect.

Best Regards,
Alexander Shereshevsky
+972-52-7460635

On Thu, Jul 2, 2015 at 5:47 PM, David G. Johnston <
david(dot)g(dot)johnston(at)gmail(dot)com> wrote:

> On Thursday, July 2, 2015, Alexander Shereshevsky <shereshevsky(at)gmail(dot)com>
> wrote:
>
>> Hello,
>>
>> I have some simple function. The returned data set is generated based on
>> view (dynamic - can be changed on daily basis).
>> So the function was defined this way:
>>
>> 1. returns setof some_view as ...
>> 2. inside the function I'm generating dynamic SQL into v_sql variable.
>> 3. return query execute v_sql
>>
>> Everything works fine if I'm running single function, like:
>> select * from function (param1, param2)
>> I'm getting the delimited fields in desired order.
>>
>> But if I want to run the function in inline mode, like:
>> select function(param1, param2) from some_table;
>> so the returned datatype is record.
>>
>> To return multiple fields, I'm trying to use:
>> select (function(param1, param2)).* from some_table;
>> But this operation has a huge performance impact, IMHO runtime multiplied
>> by number of columns - the function is executed for each column separately.
>> In my case normal inline run is about 2 seconds for 300-400 records, but
>> with ().* it's increased to 90-120 seconds.
>>
>> Thank you in advance if you can suggest me the better way.
>>
>> BR,
>> Alexander Shereshevsky
>>
>
> Use LATERAL.
>
> If that is not an option you place the unexpanded function call in a CTE
> (with) and the expand it within the main query.
>
> With funccall as ( select func(arg) from tbl )
> Select (func).* from funccall;
>
> Because, yes the function is called once for each column due to the star
> expansion. You have to keep the result as a composite type during function
> execution and then expand the composite type.
>
> David J.
>