| From: | Peter Geoghegan <pg(at)bowt(dot)ie> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Mark Dilger <mark(dot)dilger(at)enterprisedb(dot)com>, Noah Misch <noah(at)leadboat(dot)com>, Thomas Munro <thomas(dot)munro(at)gmail(dot)com>, "Andrey M(dot) Borodin" <x4mmm(at)yandex-team(dot)ru>, Stephen Frost <sfrost(at)snowman(dot)net>, Michael Paquier <michael(at)paquier(dot)xyz>, Amul Sul <sulamul(at)gmail(dot)com>, Dilip Kumar <dilipbalaut(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: pg_amcheck contrib application |
| Date: | 2021-03-23 19:53:35 |
| Message-ID: | CAH2-WzmdypcxU6LdJ_QMf0KHNpaWJK4AJKLf-YjEuCtrEvGWwA@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Tue, Mar 23, 2021 at 12:44 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> > I will make this change to HEAD soon, barring objections.
>
> +1. Not deleting the upper page seems better than the alternatives.
FWIW it might also work that way as a holdover from the old page
deletion algorithm. These days we decide exactly which pages (leaf
page plus possible internal pages) are to be deleted as a whole up
front (these are a subtree, though usually just a degenerate
single-leaf-page subtree -- internal page deletions are rare).
One of the advantages of this design is that we verify practically all
of the work involved in deleting an entire subtree up-front, inside
_bt_lock_subtree_parent(). It's clearly safe to back out of it if it
looks dicey.
--
Peter Geoghegan
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