| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Shridhar Daithankar <shridhar_daithankar(at)persistent(dot)co(dot)in> |
| Cc: | Andrew Sullivan <andrew(at)libertyrms(dot)info>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Some thoughts about i/o priorities and throttling vacuum |
| Date: | 2003-10-17 14:36:38 |
| Message-ID: | 22583.1066401398@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Shridhar Daithankar <shridhar_daithankar(at)persistent(dot)co(dot)in> writes:
> Would it be possible to have a vacuum variant that would just shuffle thr.
> shared buffers and not touch disk at all?
What would be the use of that? You couldn't predict *anything* about
the coverage. Maybe you find all the free space in a particular table,
but most likely you don't.
In any case an I/O-free vacuum is impossible since once you have decided
to recycle a particular tuple, you don't have any option about removing
the corresponding index entries first. So unless both the table and all
its indexes are in RAM, you will be incurring I/O.
regards, tom lane
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