Firebird/SQLite - TFloatField/TSingleField

[mac_srv]

Hi All,

I experienced a difference in behavior with ZeosLib 7.2.0 Beta.

1. Using Firebird
With a Firebird 2.5.2 simple database, the FLOAT fields are interpreted (I think), by ZeosLib, differently in C++Builder (RAD) 2009 and C++Builder XE2. I tested in a Windows 7 64 bits OS. In C++Builder RAD 2009, the FLOAT is interpreted as TFloatField. On the other hand, in XE2 the same field was interpreted as TSingleField.

2. Using SQLite
With a SQLite 3.8.11 equivalent database, the REAL fields are interpreted as TFloatField both in RAD 2009 and XE2.

I also noticed that TSingleFields are present in XE2 but not in RAD 2009.

I'm trying to implement a Multi-DBMS TDataModule and this subject is kind of a problem, as I have TField descendants in design time.

Is there a way to overcome this TFloatField/TSingleField mapping difference in C++Builder XE2?

Thank you in advance.

Best,

Marcelo.

[Synopses]
Windows 7 64 bits
ZeosLib 7.2.0 Beta
Firebird 2.5.2 and SQLite 3.8.11
C++Builder RAD 2009 and XE2 Professional.

[marsupilami]

Hello Marcelo,

I did not introduce that change but to me that seems like Zeos leveraging the new possibilities of new Delphi/BCB versions. The Firebird float datatype is a float with single precision. So the best option is to represent it as a TSingleField in newer Delphi and BCB versions. Delphi/BCB 2009 doesn't have a TSingleField so the only option for representing this field type was to use a TFloatField.

My suggestion: Don't use persistent fields. Let Zeos handle the creation of field objects and do the modifications to the field objects in the AfterOpen event.

Other possibilities:
1) Extend your database field to be a double precision field. I assume that this field type will always be represented by a TFloatField.
2) Modify Zeos - introduce some kind of parameter that tells the firebird driver to revert to the olf behaviour. If you want to go that route, I probably could give you some pointers on how to do that.

With best regards,

Jan

[mac_srv]

Hi Jan,

You were right, it is indeed a BCB/Delphi behavior.

Changing the respective Firebird's column to DOUBLE PRECISION resulted in a persistent TFloatField. And this is alright, because SQLite's FLOAT type has 8 bytes, as Firebird's DOUBLE PRECISION.

Also, I'll try to test your hint about using AfterOpen to avoid persistent TField descendants.

About this subject, just an extra comment: do you think ZeosLib would implement that "Data Type Mapping" as AnyDAC (now FireDAC) did?

Reference: http://docwiki.embarcadero.com/RADStudi ... FireDAC%29

If you think so, I would like to put myself as a volunteer to ZeosLib developers' group to try it.

Thank you in advance.

Marcelo.

[marsupilami]

Hello Marcelo,

currently there is not enough manpower to implement that kind of mapping. But if you want to try to do it yourself, I could try to give you some pointers. But beware because it really seems like a big task as you probably would have to modify all Zeoslib drivers and the components tha work on top of them.

With best regards,

Jan