On Sun, Aug 14, 2016 at 12:35 PM, Karsten Hilbert <Karsten.Hilbert@xxxxxxx> wrote:
On Fri, Aug 12, 2016 at 01:32:33PM +0200, Chris Travers wrote:
>>> My preference is stored procedures plus service locators
>>
>> Would you care to elaborate a little on the latter (service locators) ?
>>
>
> Sure. What I prefer to do is to allow for a (cacheable) lookup on the
> basis of some criteria, either:
> 1. Function name or
> 2. Function name and first argument type
>
> This assumes that whichever discovery criteria you are using leads to
> uniquely identifying a function.
>
> Then from the argument list, I know the names and types of the arguments,
> and the service locator can map them in. This means:
>
> 1. You can expose an API which calls arguments by name rather than just
> position, and
> 2. You can add arguments of different types without breaking things as
> long as it is agreed that unknown arguments are passed in as NULL.
Maybe I am a bit dense. Can you please give an example ?
Ok. Two ways of doing this based on different discovery criteria.. The first would be:
CREATE FUNCTION person_save(in_id int, in_first_name text, in_last_name text, in_date_of_birth date)
RETURNS person LANGUAGE ... as $$ ... $$;
Then you have a service locator that says "I have a person object and want to call person_save." It then looks up the function argument names and calls it something like this:
SELECT * FROM person_save(?, ?, ?, ?)
with parameters
$object->id, $object->first_name, $object->last_name, $object->date_of_birth
The second approach is to tie to the first argument type (think 'self' in Python).
In this case, we'd have a function defined like this:
CREATE FUNCTION save(person) RETURNS person LANGUAGE ... AS $$ ...$$;
Then we have a different service locator that maps this to the safe function as:
SELECT * FROM save(?::person);
with a argument that is basically:
serialize_to_record_form($object)
Of course that's just the start. To make this really usable you have to add some additional functionality but that should be enough to describe the process.
Thanks,
Karsten
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Best Wishes,
Chris Travers
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