[OpenSIPS-Devel] Db interface

[Bogdan-Andrei Iancu]

Hi Stan,

there are 2 way you can get the results from a DB query:

1) directly, by passing the db_res struct to the query function - it 
will return the whole result right away

2) piece by piece, after the query is done - you do not pass any db_res 
to the query function; after the query is done, you use fetch_result() 
to get a number of rows from the DB underlaying driver. You can call 
fetch_result() several time (to fetch consecutive chunks) for the same 
result in a loop (until entire result is fetched).


The second mechanism was added to be able to fetch large results via 
small pkg mem pool.

Regards,
Bogdan



Stanisław Pitucha wrote:
> Hi,
> I have some questions about the DB interface. In general - what is
> fetch_result() useful for?
> As far as I can see, every query function returns the needed results
> directly into `*_r`. In that case, why is fetch_result() needed?
>
> If it's needed, are there any guarantees about calling fetch_result? Is
> it always called directly after the query? Are there any other DB
> operations in between?
>
> Taking db_mysql as an example - how does it return any results, if every
> other query function uses mysql_store_result() directly?
>
> Thanks,
> Stan
>
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>   


-- 
Bogdan-Andrei Iancu
OpenSIPS Bootcamp
20 - 24 September 2010, Frankfurt, Germany
www.voice-system.ro