On Friday, January 12, 2024, Sébastien TANIERE <
seb.taniere@gmail.com> wrote:
Hello,
in my company, some columns rarely used in a PG database 14.8 have been set to NULL in order to save disk space (datecreation & acteurcreation in following table) .
id varchar(25) not null,
datecreation timestamp(6),
acteurcreation varchar(50),
valeurunit smallint
)
I am wondering if it is really useful for every type of column.
Intuitively, i would say that it does not save space for fixed field datecreation as it is a fixed size column.
Do we save 8 bytes by timestamp column updated to NULL or not ?
You probably should just measure it yourself. But yes, the representation of null in a tuple is the absence of data and a bit in the nulls bitmap. So there is overhead but also savings. The net effect is case specific.
David J.