| From: | Peter Geoghegan <pg(at)bowt(dot)ie> |
|---|---|
| To: | Heikki Linnakangas <hlinnaka(at)iki(dot)fi> |
| Cc: | Dmitry Dolgov <9erthalion6(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>, Alexander Korotkov <a(dot)korotkov(at)postgrespro(dot)ru>, Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com>, Claudio Freire <klaussfreire(at)gmail(dot)com>, Anastasia Lubennikova <a(dot)lubennikova(at)postgrespro(dot)ru>, "Andrey V(dot) Lepikhov" <a(dot)lepikhov(at)postgrespro(dot)ru> |
| Subject: | Re: Making all nbtree entries unique by having heap TIDs participate in comparisons |
| Date: | 2019-03-07 08:40:36 |
| Message-ID: | CAH2-WzmVaEziVcfOOBpkaETvd+dM1kvL7yj4pF5s7_APc5gRLA@mail.gmail.com |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-hackers |
On Thu, Mar 7, 2019 at 12:37 AM Peter Geoghegan <pg(at)bowt(dot)ie> wrote:
> When I drew you that picture while we were in Lisbon, I mentioned to
> you that the patch sometimes used a sentinel scantid value that was
> greater than minus infinity, but less than any real scantid. This
> could be used to force an otherwise-equal-to-pivot search to go left
> rather than uselessly going right. I explained this about 30 minutes
> in, when I was drawing you a picture.
I meant the opposite: it could be used to go right, instead of going
left when descending the tree and unnecessarily moving right on the
leaf level.
As I said, moving right on the leaf level (rather than during the
descent) should only happen when it's necessary, such as when there is
a concurrent page split. It shouldn't happen reliably when searching
for the same value, unless there really are matches across multiple
leaf pages, and that's just what we have to do.
--
Peter Geoghegan
| From | Date | Subject | |
|---|---|---|---|
| Next Message | David Steele | 2019-03-07 08:45:04 | Re: Re: Feature: temporary materialized views |
| Previous Message | Pavel Stehule | 2019-03-07 08:37:58 | Re: Re: [HACKERS] proposal: schema variables |