Re: C libpq frontend library fetchsize

Tom Lane wrote:
> Yeb Havinga <yebhavinga(at)gmail(dot)com> writes:
>
>> What if the default operation of e.g. php using libpq would be as
>> follows: set some default fetchsize (e.g. 1000 rows), then just issue
>> getrow. In the php pg handling, a function like getnextrow would wait
>> for the first pgresult with 1000 rows. Then if the pgresult is depleted
>> or almost depleted, request the next pgresult automatically. I see a lot
>> of benefits like less memory requirements in libpq, less new users with
>> why is my query so slow before the first row, and almost no concerns.
>>
>
> You are blithely ignoring the reasons why libpq doesn't do this. The
> main one being that it's impossible to cope sanely with queries that
> fail partway through execution.
I'm sorry I forgot to add a reference to your post of
http://archives.postgresql.org/pgsql-general/2010-02/msg00956.php which
is the only reference to queries failing partway that I know of. But
blithely is not a good description of me ignoring it. I though about how
queries could fail, but can't think of anything else than e.g. memory
exhaustion, and that is just one of the things that is improved this
way. Maybe a user defined type with an error on certain data values, but
then the same arguing could be: why support UDT? And if a query fails
during execution, does that mean that the rows returned until that point
are wrong?
> The described implementation would not
> cope tremendously well with nonsequential access to the resultset, either.
>
That's why I'm not proposing to replace the current way pgresults are
made complete, but just an extra option to enable developers using the
libpq libary making the choice themselves.

regards,
Yeb Havinga