| From: | Peter Geoghegan <pg(at)bowt(dot)ie> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: MinIndexTupleSize seems slightly wrong |
| Date: | 2018-04-14 17:36:30 |
| Message-ID: | CAH2-Wz=kGa3pQbG1nbuvL0htKA7=u2=XBdBzPTVsOrB8xHLBQA@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Fri, Apr 13, 2018 at 10:45 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> As long as btree only has one no-data tuple per page, I think we are good,
> because this calculation does not account for page special space. We might
> be underestimating how many tuples can fit by one MAXALIGN quantum, but
> the special space takes up at least one MAXALIGN quantum, so it's safe.
>
> Twouldn't be a bad idea to document this reasoning, though.
Thanks for taking care of this.
> Also, my first reaction on looking at this code was "who added
> MinIndexTupleSize and then didn't replace the equivalent subexpression
> of MaxIndexTuplesPerPage with MinIndexTupleSize?".
I had the same reaction.
--
Peter Geoghegan
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