Re: [RFC PATCH 0/5] oidmap: handle entries with the same key

From: Junio C Hamano <gitster@pobox.com>
Date: Jul 8, 2019, 20:24 UTC
Message-ID: <xmqqd0ikxok6.fsf@gitster-ct.c.googlers.com>
In-Reply-To: <20190707083002.7037-1-chriscool@tuxfamily.org>

Christian Couder <christian.couder@gmail.com> writes:

> This is an RFC patch series that is not intended to be merged for now,
> as it looks like we don't need oidmaps that can handle several entries
> with the same key yet.

What does it even mean for a map to allow multiple entries per key? When you have a key and its value, you must retrieve all existing entries for the key and see their values before deciding if you want to add yet another entry to the already existing set? When you have a key, you must retrieve all existing entries to see if any of them is what you want?

What I am wondering is if people usually do "a single list/set of values that is associated with each key" for such an application. Obviously you do not need a map that allows multiple entries per key if you did so---is there an advantage of a map that allows multiple entries per key?

> As I needed this for my work on reftable, I thought that...

I actually think that showing how it is used in the real application (reftable?) is the best way to illustrate why this is useful and to get opinions from others.