Hannu Krosing <[EMAIL PROTECTED]> writes:
> Ãhel kenal päeval, N, 2006-03-02 kell 09:53, kirjutas Zeugswetter
> Andreas DCP SD:
>> Ok, we cannot reuse a dead tuple. Maybe we can reuse the space of a dead
>> tuple by reducing the tuple to it's header info.
> I don't even think you need the header, just truncate the slot to be
> 0-size
I think you must keep the header because the tuple might be part of an
update chain (cf vacuuming bugs we repaired just a few months ago).
t_ctid is potentially interesting data even in a certainly-dead tuple.
Andreas' idea is possibly doable but I am not sure that I see the point.
It does not reduce the need for vacuum nor the I/O load imposed by
vacuum. What it does do is bias the system in the direction of
allocating an unreasonably large number of tuple line pointers on a page
(ie, more than are useful when the page is fully packed with normal
tuples). Since we never reclaim such pointers, over time all the pages
in a table would tend to develop line-pointer-bloat. I don't know what
the net overhead would be, but it'd definitely impose some aggregate
inefficiency.
regards, tom lane
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