Re: session level locks

"Jenny -" <nat_lazy@hotmail.com> writes:
> hi, does anyone know what session level locks mean in postgresql..i've heard 
> of table-level locks and row level locks but not session level

It's a hack for VACUUM.  VACUUM needs to run two transactions to
vacuum both a table and its toast table; plus another one if it's
going to ANALYZE.  Ordinary locks would go away at transaction
commit.  Session locks are used to ensure the table doesn't disappear
till we're done vacuuming.

I doubt that session locks as currently designed are good for anything
except VACUUM.  They *do* go away on error abort --- which is exactly
what VACUUM wants, but is unlikely to be useful behavior for anything
else.
        regards, tom lane