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From: Patrick Steinhardt <ps@pks.im>
To: Jeff King <peff@peff.net>
Cc: git@vger.kernel.org,
	Christian Couder <christian.couder@gmail.com>,
	Taylor Blau <me@ttaylorr.com>
Subject: Re: [PATCH v2 2/8] revision: mark commit parents as NOT_USER_GIVEN
Date: Fri, 9 Apr 2021 12:19:38 +0200	[thread overview]
Message-ID: <YHAqOj+vboM+9f7d@ncase> (raw)
In-Reply-To: <YGya0XY969HlyPWl@coredump.intra.peff.net>

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On Tue, Apr 06, 2021 at 01:30:57PM -0400, Jeff King wrote:
> On Mon, Mar 15, 2021 at 02:14:36PM +0100, Patrick Steinhardt wrote:
> 
> > The NOT_USER_GIVEN flag of an object marks whether a flag was explicitly
> > provided by the user or not. The most important use case for this is
> > when filtering objects: only objects that were not explicitly requested
> > will get filtered.
> > 
> > The flag is currently only set for blobs and trees, which has been fine
> > given that there are no filters for tags or commits currently. We're
> > about to extend filtering capabilities to add object type filter though,
> > which requires us to set up the NOT_USER_GIVEN flag correctly -- if it's
> > not set, the object wouldn't get filtered at all.
> > 
> > Mark unseen commit parents as NOT_USER_GIVEN when processing parents.
> > Like this, explicitly provided parents stay user-given and thus
> > unfiltered, while parents which get loaded as part of the graph walk
> > can be filtered.
> > 
> > This commit shouldn't have any user-visible impact yet as there is no
> > logic to filter commits yet.
> 
> I'm still scratching my head a bit to understand how NOT_USER_GIVEN can
> possibly be correct (as opposed to USER_GIVEN). If we visit the commit
> in a not-user-given context and add the flag, how do we know it wasn't
> _also_ visited in a user-given context?
> 
> Just guessing, but perhaps the SEEN flag is saving us here? If we visit
> the user-given commit itself first, then we give it the SEEN flag. Then
> if we try to visit it again via parent traversal, we've already
> processed it and don't add the NOT_USER_GIVEN flag here.

Yes, I think that's mostly it.

> That seems the opposite of the order we'd usually traverse, but I think
> we set SEEN on each commit in prepare_revision_walk(), before we do any
> traversing.
> 
> So I _think_ it all works even with your changes here, but I have to say
> this NOT_USER_GIVEN thing seems really fragile to me. Not new in your
> series, of course, but something we may want to look at.
> 
> Just grepping around, "rev-list -g" will happily remove SEEN flags, so I
> suspect it interacts badly with --filter. Just trying "rev-list -g
> --objects --filter=object:type=blob HEAD" shows that it produces quite a
> lot of commits (which I think is a more fundamental problem: it is not
> walking the parent chain at all to assign these NOT_USER_GIVEN flags).

I totally agree that this feels fragile, and developing this series with
NOT_USER_GIVEN wasn't the most enjoyable experience either. I wouldn't
love to be doing the conversion back to USER_GIVEN as part of this
series, but I wouldn't oppose doing that job either. Right now I don't
feel like I'm sufficiently sure that it's working for all cases, and
indeed your example with "rev-list -g" already shows one case where it's
breaking.

So let me know whether I should add the conversion as preparatory step.

Patrick

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  reply	other threads:[~2021-04-09 10:22 UTC|newest]

Thread overview: 97+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-01 12:20 [PATCH 0/7] rev-parse: implement object type filter Patrick Steinhardt
2021-03-01 12:20 ` [PATCH 1/7] revision: mark commit parents as NOT_USER_GIVEN Patrick Steinhardt
2021-03-01 12:20 ` [PATCH 2/7] list-objects: move tag processing into its own function Patrick Steinhardt
2021-03-01 12:20 ` [PATCH 3/7] list-objects: support filtering by tag and commit Patrick Steinhardt
2021-03-01 12:20 ` [PATCH 4/7] list-objects: implement object type filter Patrick Steinhardt
2021-03-01 12:20 ` [PATCH 5/7] pack-bitmap: " Patrick Steinhardt
2021-03-01 12:20 ` [PATCH 6/7] pack-bitmap: implement combined filter Patrick Steinhardt
2021-03-01 12:21 ` [PATCH 7/7] rev-list: allow filtering of provided items Patrick Steinhardt
2021-03-10 21:39 ` [PATCH 0/7] rev-parse: implement object type filter Jeff King
2021-03-11 14:38   ` Patrick Steinhardt
2021-03-11 17:54     ` Jeff King
2021-03-15 11:25   ` Patrick Steinhardt
2021-03-10 21:58 ` Taylor Blau
2021-03-10 22:19   ` Jeff King
2021-03-11 14:43     ` Patrick Steinhardt
2021-03-11 17:56       ` Jeff King
2021-03-15 13:14 ` [PATCH v2 0/8] " Patrick Steinhardt
2021-03-15 13:14   ` [PATCH v2 1/8] uploadpack.txt: document implication of `uploadpackfilter.allow` Patrick Steinhardt
2021-04-06 17:17     ` Jeff King
2021-03-15 13:14   ` [PATCH v2 2/8] revision: mark commit parents as NOT_USER_GIVEN Patrick Steinhardt
2021-04-06 17:30     ` Jeff King
2021-04-09 10:19       ` Patrick Steinhardt [this message]
2021-03-15 13:14   ` [PATCH v2 3/8] list-objects: move tag processing into its own function Patrick Steinhardt
2021-04-06 17:39     ` Jeff King
2021-03-15 13:14   ` [PATCH v2 4/8] list-objects: support filtering by tag and commit Patrick Steinhardt
2021-03-15 13:14   ` [PATCH v2 5/8] list-objects: implement object type filter Patrick Steinhardt
2021-04-06 17:42     ` Jeff King
2021-03-15 13:14   ` [PATCH v2 6/8] pack-bitmap: " Patrick Steinhardt
2021-04-06 17:48     ` Jeff King
2021-03-15 13:14   ` [PATCH v2 7/8] pack-bitmap: implement combined filter Patrick Steinhardt
2021-04-06 17:54     ` Jeff King
2021-04-09 10:31       ` Patrick Steinhardt
2021-04-09 15:53         ` Jeff King
2021-04-09 11:17       ` Patrick Steinhardt
2021-04-09 15:55         ` Jeff King
2021-03-15 13:15   ` [PATCH v2 8/8] rev-list: allow filtering of provided items Patrick Steinhardt
2021-04-06 18:04     ` Jeff King
2021-04-09 10:59       ` Patrick Steinhardt
2021-04-09 15:58         ` Jeff King
2021-03-20 21:10   ` [PATCH v2 0/8] rev-parse: implement object type filter Junio C Hamano
2021-04-06 18:08     ` Jeff King
2021-04-09 11:14       ` Patrick Steinhardt
2021-04-09 16:05         ` Jeff King
2021-04-09 11:27   ` [PATCH v3 " Patrick Steinhardt
2021-04-09 11:27     ` [PATCH v3 1/8] uploadpack.txt: document implication of `uploadpackfilter.allow` Patrick Steinhardt
2021-04-09 11:27     ` [PATCH v3 2/8] revision: mark commit parents as NOT_USER_GIVEN Patrick Steinhardt
2021-04-09 11:28     ` [PATCH v3 3/8] list-objects: move tag processing into its own function Patrick Steinhardt
2021-04-09 11:28     ` [PATCH v3 4/8] list-objects: support filtering by tag and commit Patrick Steinhardt
2021-04-11  6:49       ` Junio C Hamano
2021-04-09 11:28     ` [PATCH v3 5/8] list-objects: implement object type filter Patrick Steinhardt
2021-04-09 11:28     ` [PATCH v3 6/8] pack-bitmap: " Patrick Steinhardt
2021-04-09 11:28     ` [PATCH v3 7/8] pack-bitmap: implement combined filter Patrick Steinhardt
2021-04-09 11:28     ` [PATCH v3 8/8] rev-list: allow filtering of provided items Patrick Steinhardt
2021-04-09 11:32       ` [RESEND PATCH " Patrick Steinhardt
2021-04-09 15:00       ` [PATCH " Philip Oakley
2021-04-12 13:15         ` Patrick Steinhardt
2021-04-11  6:02     ` [PATCH v3 0/8] rev-parse: implement object type filter Junio C Hamano
2021-04-12 13:12       ` Patrick Steinhardt
2021-04-12 13:37     ` [PATCH v4 0/8] rev-list: " Patrick Steinhardt
2021-04-12 13:37       ` [PATCH v4 1/8] uploadpack.txt: document implication of `uploadpackfilter.allow` Patrick Steinhardt
2021-04-12 13:37       ` [PATCH v4 2/8] revision: mark commit parents as NOT_USER_GIVEN Patrick Steinhardt
2021-04-12 13:37       ` [PATCH v4 3/8] list-objects: move tag processing into its own function Patrick Steinhardt
2021-04-12 13:37       ` [PATCH v4 4/8] list-objects: support filtering by tag and commit Patrick Steinhardt
2021-04-12 13:37       ` [PATCH v4 5/8] list-objects: implement object type filter Patrick Steinhardt
2021-04-13  9:57         ` Ævar Arnfjörð Bjarmason
2021-04-13 10:43           ` Andreas Schwab
2021-04-14 11:32           ` Patrick Steinhardt
2021-04-12 13:37       ` [PATCH v4 6/8] pack-bitmap: " Patrick Steinhardt
2021-04-12 13:37       ` [PATCH v4 7/8] pack-bitmap: implement combined filter Patrick Steinhardt
2021-04-12 13:37       ` [PATCH v4 8/8] rev-list: allow filtering of provided items Patrick Steinhardt
2021-04-13  7:45       ` [PATCH v4 0/8] rev-list: implement object type filter Jeff King
2021-04-13  8:06         ` Patrick Steinhardt
2021-04-15  9:42           ` Jeff King
2021-04-16 22:06             ` Junio C Hamano
2021-04-16 23:15               ` Junio C Hamano
2021-04-17  1:17                 ` Ramsay Jones
2021-04-17  9:01                   ` Jeff King
2021-04-17 21:45                     ` Junio C Hamano
2021-04-13 21:03         ` Junio C Hamano
2021-04-14 11:59           ` Patrick Steinhardt
2021-04-14 21:07             ` Junio C Hamano
2021-04-15  9:57               ` Jeff King
2021-04-15 17:53                 ` Junio C Hamano
2021-04-15 17:57                   ` Junio C Hamano
2021-04-17  8:58                     ` Jeff King
2021-04-19 11:46       ` [PATCH v5 " Patrick Steinhardt
2021-04-19 11:46         ` [PATCH v5 1/8] uploadpack.txt: document implication of `uploadpackfilter.allow` Patrick Steinhardt
2021-04-19 11:46         ` [PATCH v5 2/8] revision: mark commit parents as NOT_USER_GIVEN Patrick Steinhardt
2021-04-19 11:46         ` [PATCH v5 3/8] list-objects: move tag processing into its own function Patrick Steinhardt
2021-04-19 11:46         ` [PATCH v5 4/8] list-objects: support filtering by tag and commit Patrick Steinhardt
2021-04-19 11:46         ` [PATCH v5 5/8] list-objects: implement object type filter Patrick Steinhardt
2021-04-19 11:46         ` [PATCH v5 6/8] pack-bitmap: " Patrick Steinhardt
2021-04-19 11:47         ` [PATCH v5 7/8] pack-bitmap: implement combined filter Patrick Steinhardt
2021-04-19 11:47         ` [PATCH v5 8/8] rev-list: allow filtering of provided items Patrick Steinhardt
2021-04-19 23:16         ` [PATCH v5 0/8] rev-list: implement object type filter Junio C Hamano
2021-04-23  9:13           ` Jeff King
2021-04-28  2:18             ` Junio C Hamano

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