[fpc-devel] TField.AsString and Databases with UTF-8 charset

[Joost van der Sluis]

Op vrijdag 24-07-2009 om 15:31 uur [tijdzone +0200], schreef Michael Van
Canneyt:
> 
> On Fri, 24 Jul 2009, Graeme Geldenhuys wrote:
> 
> > Michael Van Canneyt wrote:
> >>> No, not a second query, just keeping track of extra (other) meta data 
> >>> information which was retrieved from the first API call to Firebird.
> >> 
> >> My databases are HUGE, and I don't think that such a query is appropriate.
> >
> >
> > It's got nothing to do with the size of your database. It is simply SqlDB 
> > that is using the wrong field to report the size of the Char(x) field 
> > definitions.
> 
> Which field should it use according to you then ?

And, Graeme, we need a field that is accesible through the
Firebird-C-API, not by some query we can run. 

> 1. Foresee a charsize field in TStringField

Yes, or (ab?)use .Size for that, as we also have .DataSize. Depends on
Delphi2009, I would say. 
Normally for TStringFields, Size is DataSize-1. I don't know if it leads
to any problems when we change that.

And note that this is not implemented in sqldb, nor TBufDataset, but
TDataset/TStringField itself...

> 2. Map UTF8 fields to widestring and convert them on the go.

With a property to set this, this seems ok

> 3. Introduce a TUTF8field which equals TStringField, but which reserves
>     a buffer of 4 bytes per character.

Yes, or make it variable-length. In that case we can use part of
Martin's code. And not

> At that point, the firebird connection must be adapted to report the 
> character length instead of the buffer length.

Which can be difficult, I don't know if they added an api-call for this.
Else we have to calculate the length ourselves by looping through the
characters. But if TDataset should do that or the end-uprogrammer, I
don't know.

Joost.