Re: [Firebird-devel] VARCHAR data compression in Firebird 2.1.x

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

Ann,

> There aren't any bits in the field header.  In fact, there isn't any
> field header.  There's the record header followed by some number of
> bytes of null flags, where each byte holds eight null flags, so a
> table with 1 field has one byte of which one bit is used. A table
> with two fields has one byte of which two bits are used. A table
> with nine fields has two bytes of which nine bits are used and
> seven are not, etc.

IIRC, the null mask cannot consist of one or two bytes, instead it 
occupies 4 or 8 or 12 etc bytes.


Dmitry