Firebird specials in table structure for varchar and UTF-8

Nov 15

In my Visual Objects applications based on DBFs I have a routine that checks the structure of the DBF tables, compares them with the structure that is required and adjusts the structure.

I’m now working on a similar functionality for my Firebird based .NET applications. To retrieve the list of the currently existing user tables, I’m using such a statement:

select rdb$relation_name as tablename from rdb$relations
where rdb$view_blr is null and 
(rdb$system_flag is null or rdb$system_flag = 0)

and to retrieve the actual structure of such a table I use the following statement:

select rf.rdb$field_position as fieldpos, 
TRIM(rf.rdb$field_name) as fieldname, 
f.rdb$field_type as fieldtype, 
f.rdb$field_length as fieldlen,
f.rdb$field_scale as fielddec, 
(f.rdb$null_flag = 1) OR (rf.rdb$null_flag = 1) as canbenull 
from rdb$relation_fields rf 
JOIN rdb$fields f ON f.rdb$field_name = rf.rdb$field_source 
WHERE upper( rf.rdb$relation_name ) = upper( 'mytable' ) 
order by rf.rdb$field_position

To have no limitations with foreign languages, I have opted to use the UTF-8 character set for all varchar columns.

And now I was very surprised: the select statement returned 4 times the actual field width: for a field defined as varchar(20) the query returned 80 as field length.

My conclusion is very simple: since every UTF-8 character can take up to 4 bytes, Firebird reserves 4 bytes for every character.

I have now found the following StackOwerflow article about this:

Firebird 3.0, Embedded server and the .NET provider

Nov 15

For local data, the embedded server of Firebird is very welcome because it does not needs any configuration.

With Firebird 2.5, a special DLL (fbembed.dll) was needed, but Firebird 3.0 has added this functionality into the standard fbclient.dll.
So, if using the embedded server of Firebird 3.0 instead of the one of Firebird 2.5, you need to specify this in the connection string. It is the best to use the ClientLibrary property of the FBConnectionStringBuilder (namespace FirebirdSql.Data.FirebirdClient).

The following files need to be put in your application directory (please make attention to use the correct bitness – 64 bit files for a 64 bit application and 32 bit files for a 32 bit application):

Normally, you should NOT need to put a firebird.conf file in you application directory.