Re: Adding columns dynamically to a table

"Avinash Lakshman" <avinash(dot)lakshman(at)gmail(dot)com> writes:
> I am new to PostGres and I am evaluating it for our purposes. The biggest
> requirement I have is that I need the ability to constantly add columns
> dynamically to a table. How is the efficiency of such an operation ?

Adding a column is nearly free (just a few system-catalog updates) if
you are willing to have it filled with NULLs initially.

Populating it with values could be pretty expensive --- whole-table
UPDATE is not really PG's strongest point.

Also, how many columns does "constantly" add up to? There's a hard
limit of something like 1600 columns per table, and in practice you
don't want to have more than a couple hundred. If you think you need
enormously wide tables, perhaps it's time to rethink your schema.

regards, tom lane