Re: [Firebird-devel] DSQL API

[Dmitry Y. <fir...@ya...>]

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.

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.


Dmitry