Re: Aggressive freezing in lazy-vacuum

ITAGAKI Takahiro <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp> writes:
> Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> I said nothing about expired tuples. The point of not freezing is to
>> preserve information about the insertion time of live tuples.

> I don't know what good it will do -- for debugging?

Exactly. As an example, I've been chasing offline a report from Merlin
Moncure about duplicate entries in a unique index; I still don't know
what exactly is going on there, but the availability of knowledge about
which transactions inserted which entries has been really helpful. If
we had a system designed to freeze tuples as soon as possible, that info
would have been gone forever pretty soon after the problem happened.

I don't say that this behavior can never be acceptable, but you need
much more than a marginal performance improvement to convince me that
it's worth the loss of forensic information.

regards, tom lane