On Mon, Jul 1, 2019 at 7:28 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Even more interesting, the same para also exists verbatim in
> v4r2's src/backend/access/nobtree/nobtpage.c, which is dated 1991-10-29
> in the same tarball. (If you're wondering, "nobtree" seems to stand
> for "no-overwrite btree"; so I suppose it went the way of all flesh
> when Stonebraker lost interest in write-once mass storage.) So presumably
> this comment dates back to some common ancestor of the mainline btree code
> and the no-overwrite code, which must have been even older than the 1991
> date.
"no-overwrite btree" is described here, if you're interested:
https://pdfs.semanticscholar.org/a0de/438d5efd96e8af51bc7595aa1c30d0497a57.pdf
This is a link to the B-Tree focused paper "An Index Implementation
Supporting Fast Recovery for the POSTGRES Storage System". I found
that the paper provided me with some interesting historic context. I
am pretty sure that the authors were involved in early work on the
Postgres B-Tree code. It references Lanin and Shasha, even though the
nbtree code that is influenced by L&S first appears in the same 2003
commit of yours that I mentioned.
> > I think that the whole sentence about "the standard class of race
> > conditions" should go. There is no more dance. Nothing in
> > _bt_getroot() is surprising to me. The other comments explain things
> > comprehensively.
>
> +1
I'll take care of it soon.
--
Peter Geoghegan