Re: [Firebird-devel] DSQL API

[Adriano d. S. F. <adr...@gm...>]

Dmitry Yemanov wrote:
> Adriano,
> 
>> When it offers a flexibility (allowing, well, requiring) you to pass a
>> output SQLDA in each fetch, it need to parse it and create messages  at
>> every function call. Seems the reason that Dimitry S. says DSQL queries
>> are much slower than BLR ones.
>>
>> In GDS_DSQL_FETCH, this piece should be slow:
>> USHORT blr_length, msg_type, msg_length;
>> if (UTLD_parse_sqlda(status,&dasup,&blr_length,&msg_type,
>> 	&msg_length, dialect, sqlda, DASUP_CLAUSE_select))
>> {
>> 	return status[1];
>> }
>>
>> And in the function start:
>> if (!sqlda)
>> {
>> 	status_exception::raise(Arg::Gds(isc_dsql_sqlda_err));
>> }
>>
>> I think we can allow DSQL_FETCH to be called with NULL sqlda when
>> DSQL_EXECUTE2 has been called with a non-null out_sqlda. In this case we
>> don't need to reparse it at every fetch.
> 
> Perhaps we could also allow DSQL_FETCH to be called with NULL sqlda if 
> any prior DSQL_FETCH calls were with non-null sqlda. In other words, we 
> should just cache the most recently used non-null output sqlda and use 
> it when user specifies null output SQLDA. I agree it would be an useful 
> improvement.
> 
Also possible.

> Another related thing (from memory, so I may be imprecise) could be to 
> still parse the (non-null) output sqlda but don't recreate the output 
> message every time.

...

> Just compare the current sqlda with the priorly used 
> one and reuse the last message if sqlda hasn't changed.
> 
I thought on storing the last sqlda value and comparing it with the passed one, and totally skip the UTLD call.

It would make applications faster automatically, but there will be a potential problem, if the user pass the same sqlda with something changed. I don't think users are doing that, but is something valid currently.

Do you mean the same thing? If not, I didn't understood the "still parse ... but don't recreate ..." part.


Adriano