remove redundant check of item pointer

Started by Junwang Zhaoover 4 years ago3 messageshackers
Beta feature

Hackorum builds and tests every patch posted to the lists, not only commitfest submissions. This is Hackorum's own CI rather than the PostgreSQL project's, and it is still under testing - please report anything that looks wrong.

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You can run a PostgreSQL built from this patch straight from Docker, with no checkout and no build:

docker run --rm -p 5432:5432 ghcr.io/hackorum-dev/postgres-patch:t45879
psql -h localhost -U postgres

Built from patchset v1 (message #1), September 20, 2026 at 05:54 AM.

Every patchset is also pushed to a branch of our PostgreSQL fork, so you can check out the same tree CI built. Without a PostgreSQL checkout:

git clone --branch t45879_1 https://github.com/hackorum-dev/postgres.git

In a checkout you already have, add the fork once:

git remote add hackorum https://github.com/hackorum-dev/postgres.git

then, for this patchset and every later one:

git fetch hackorum t45879_1 && git checkout t45879_1

Patchset v1 (message #1) is on t45879_1

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#1Junwang Zhao
zhjwpku@gmail.com

In function ItemPointerEquals, the ItemPointerGetBlockNumber
already checked the ItemPointer if valid, there is no need
to check it again in ItemPointerGetOffset, so use
ItemPointerGetOffsetNumberNoCheck instead.

--
Regards
Junwang Zhao

Attachments:

t45879_1
v1-0001-remove-redundant-check-of-item-pointer.patchapplication/octet-stream; name=v1-0001-remove-redundant-check-of-item-pointer.patchDownload+2-3
#2Tom Lane
tgl@sss.pgh.pa.us
In reply to: Junwang Zhao (#1)
Re: remove redundant check of item pointer

Junwang Zhao <zhjwpku@gmail.com> writes:

In function ItemPointerEquals, the ItemPointerGetBlockNumber
already checked the ItemPointer if valid, there is no need
to check it again in ItemPointerGetOffset, so use
ItemPointerGetOffsetNumberNoCheck instead.

I do not think this change is worth making. The point of
ItemPointerGetOffsetNumberNoCheck is not to save some cycles,
it's to be able to fetch the offset field in cases where it might
validly be zero. The assertion will be compiled out anyway in
production builds --- and even in assert-enabled builds, I'd kind
of expect the compiler to optimize away the duplicated tests.

regards, tom lane

#3Junwang Zhao
zhjwpku@gmail.com
In reply to: Tom Lane (#2)
Re: remove redundant check of item pointer

got it, thanks for the explanation.

On Wed, Apr 27, 2022 at 11:34 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:

Junwang Zhao <zhjwpku@gmail.com> writes:

In function ItemPointerEquals, the ItemPointerGetBlockNumber
already checked the ItemPointer if valid, there is no need
to check it again in ItemPointerGetOffset, so use
ItemPointerGetOffsetNumberNoCheck instead.

I do not think this change is worth making. The point of
ItemPointerGetOffsetNumberNoCheck is not to save some cycles,
it's to be able to fetch the offset field in cases where it might
validly be zero. The assertion will be compiled out anyway in
production builds --- and even in assert-enabled builds, I'd kind
of expect the compiler to optimize away the duplicated tests.

regards, tom lane

--
Regards
Junwang Zhao