From: Duy Nguyen <pclouds@gmail.com>
To: David Turner <dturner@twopensource.com>
Cc: Git Mailing List <git@vger.kernel.org>, Jeff King <peff@peff.net>,
Michael Haggerty <mhagger@alum.mit.edu>,
Junio C Hamano <gitster@pobox.com>
Subject: Re: [PATCH v7 31/33] refs: add LMDB refs storage backend
Date: Tue, 1 Mar 2016 08:45:50 +0700 [thread overview]
Message-ID: <CACsJy8A8rwcKFb_fH2BZN=nuqMdhA2u8xCP4fN0KZmDAczQPog@mail.gmail.com> (raw)
In-Reply-To: <1456796138.18017.77.camel@twopensource.com>
On Tue, Mar 1, 2016 at 8:35 AM, David Turner <dturner@twopensource.com> wrote:
> On Tue, 2016-03-01 at 08:31 +0700, Duy Nguyen wrote:
>> On Tue, Mar 1, 2016 at 7:53 AM, David Turner <
>> dturner@twopensource.com> wrote:
>> > +Weaknesses:
>> > +-----------
>> > +
>> > +The reflog format is somewhat inefficient: a binary format could
>> > store
>> > +reflog date/time information in somewhat less space.
>>
>> This raises an interesting question. What if we want to change lmdb
>> format in future (e.g. to address this weakness)? Do we need some
>> sort
>> of versioning in lmdb database? I suppose you can always add "lmdb2"
>> backend that shares most of the code with current lmdb backend. Not
>> sure if that's what you had in mind though.
>
> The weakness of versioning inside the LMDB database is that in order to
> check the version, you need to already have LMDB. That's the argument
> for "lmdb2".
>
> I had sort of hoped that this version would be "good enough" that we
> could avoid modifying it. So maybe that means we ought to address the
> reflog format. But I'm not sure that it's that big a deal. What do
> you think?
I'm not using lmdb yet (can't because if I convert my git.git to use
it, all topics I'm working on must be rebased on lmdb :-( ) so I don't
have any strong opinion about this. As long as we have an escape hatch
(that won't lead to a too messy future) I think we're good.
Note that storing in binary also has disadvantage. If we move from
SHA-1 to SHA-XXX in future, we can easily detect incorrect reflog line
in text form, it's a bit harder to do in binary form when you pack
everything (including some variable stuff like email) in one value.
But I think we don't have to care about that right now, there will be
lots of problems migrating to SHA-XXX anyway.
--
Duy
next prev parent reply other threads:[~2016-03-01 1:46 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-01 0:52 [PATCH v7 00/33] refs backend David Turner
2016-03-01 0:52 ` [PATCH v7 01/33] setup: call setup_git_directory_gently before accessing refs David Turner
2016-03-01 8:35 ` Jeff King
2016-03-01 23:47 ` David Turner
2016-03-02 0:33 ` David Turner
2016-03-02 2:45 ` Jeff King
2016-03-01 0:52 ` [PATCH v7 02/33] refs: move head_ref{,_submodule} to the common code David Turner
2016-03-01 0:52 ` [PATCH v7 03/33] refs: move for_each_*ref* functions into " David Turner
2016-03-01 0:52 ` [PATCH v7 04/33] files-backend: break out ref reading David Turner
2016-03-20 5:03 ` Michael Haggerty
2016-03-22 8:33 ` Michael Haggerty
2016-03-23 10:19 ` Michael Haggerty
2016-03-01 0:52 ` [PATCH v7 05/33] refs: move resolve_ref_unsafe into common code David Turner
2016-03-01 0:52 ` [PATCH v7 06/33] refs: add a backend method structure with transaction functions David Turner
2016-03-01 0:52 ` [PATCH v7 07/33] refs: add methods for misc ref operations David Turner
2016-03-01 0:52 ` [PATCH v7 08/33] refs: add method for do_for_each_ref David Turner
2016-03-01 0:52 ` [PATCH v7 09/33] refs: reduce the visibility of do_for_each_ref() David Turner
2016-03-24 7:07 ` Michael Haggerty
2016-03-24 18:56 ` David Turner
2016-03-01 0:52 ` [PATCH v7 10/33] refs: add do_for_each_per_worktree_ref David Turner
2016-03-01 0:52 ` [PATCH v7 11/33] refs: add methods for reflog David Turner
2016-03-01 0:52 ` [PATCH v7 12/33] refs: add method for initial ref transaction commit David Turner
2016-03-01 0:52 ` [PATCH v7 13/33] refs: add method for delete_refs David Turner
2016-03-01 0:52 ` [PATCH v7 14/33] refs: add methods to init refs db David Turner
2016-03-24 7:28 ` Michael Haggerty
2016-03-24 18:04 ` David Turner
2016-03-01 0:52 ` [PATCH v7 15/33] refs: add method to rename refs David Turner
2016-03-01 0:52 ` [PATCH v7 16/33] refs: handle non-normal ref renames David Turner
2016-03-01 0:52 ` [PATCH v7 17/33] refs: make lock generic David Turner
2016-03-24 19:45 ` Michael Haggerty
2016-03-01 0:52 ` [PATCH v7 18/33] refs: move duplicate check to common code David Turner
2016-03-01 0:52 ` [PATCH v7 19/33] refs: allow log-only updates David Turner
2016-04-21 14:17 ` Michael Haggerty
2016-04-25 16:46 ` David Turner
2016-03-01 0:52 ` [PATCH v7 20/33] refs: don't dereference on rename David Turner
2016-03-01 0:52 ` [PATCH v7 21/33] refs: on symref reflog expire, lock symref not referrent David Turner
2016-03-01 0:52 ` [PATCH v7 22/33] refs: resolve symbolic refs first David Turner
2016-03-01 0:52 ` [PATCH v7 23/33] refs: always handle non-normal refs in files backend David Turner
2016-03-01 0:52 ` [PATCH v7 24/33] init: allow alternate ref strorage to be set for new repos David Turner
2016-03-01 0:52 ` [PATCH v7 25/33] refs: check submodules' ref storage config David Turner
2016-03-01 0:52 ` [PATCH v7 26/33] clone: allow ref storage backend to be set for clone David Turner
2016-03-01 0:53 ` [PATCH v7 27/33] svn: learn ref-storage argument David Turner
2016-03-01 0:53 ` [PATCH v7 28/33] refs: register ref storage backends David Turner
2016-03-01 0:53 ` [PATCH v7 29/33] setup: configure ref storage on setup David Turner
2016-03-01 8:48 ` Jeff King
2016-03-01 14:50 ` Jeff King
2016-03-01 17:18 ` Ramsay Jones
2016-03-01 19:16 ` David Turner
2016-03-01 0:53 ` [PATCH v7 30/33] refs: break out resolve_ref_unsafe_submodule David Turner
2016-03-01 17:21 ` Ramsay Jones
2016-03-01 19:17 ` David Turner
2016-03-01 0:53 ` [PATCH v7 31/33] refs: add LMDB refs storage backend David Turner
2016-03-01 1:31 ` Duy Nguyen
2016-03-01 1:35 ` David Turner
2016-03-01 1:45 ` Duy Nguyen [this message]
2016-03-01 0:53 ` [PATCH v7 32/33] refs: tests for lmdb backend David Turner
2016-03-01 0:53 ` [PATCH v7 33/33] tests: add ref-storage argument David Turner
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