Re: size cost for null fields

"Vance Maverick" <vmaverick(at)pgp(dot)com> writes:

> Do I have this right? If so, the side table sounds like the right choice....

No, if the null bit is set then the field isn't stored at all. You don't pay
the alignment or storage overhead at all.

The only cost is for the null bitmap itself. If you have *any* null fields
then you pay one bit for *every* field plus alignment to a 4-byte boundary.
Except there's one available free byte so if you have 8 or fewer fields even
that is entirely free.

--
Gregory Stark
EnterpriseDB http://www.enterprisedb.com
Get trained by Bruce Momjian - ask me about EnterpriseDB's PostgreSQL training!