On 14.02.2014 11:38, Julian Foad wrote:
> Marc Strapetz wrote:
>> For SmartSVN we are optionally displaying merge arrows in the Revision
>> Graph. Here is a sample image, how this looks like:
>>
>> http://imgur.com/MzrLq00
>>
>>> From the JavaHL sources I understand that there is currently only one
>>> method to retrieve server-side mergeinfo and this one works on a single
>>> revision only:
>>
>> Map<String, Mergeinfo> getMergeinfo(Iterable<String> paths,
>> long revision,
>> Mergeinfo.Inheritance inherit,
>> boolean includeDescendants)
>
> Right. This is a wrapper around the core library function
> svn_ra_get_mergeinfo().
>
>> This makes the Merge Arrow feature practically unusable for larger graphs.
>>
>> To improve performance, in earlier versions we were using a client-side
>> mergeinfo cache (similar as the main log-cache, which TSVN is using as
>> well). However, populating this cache (i.e. querying for mergeinfo for
>> *every* revision of the repository) often resulted in bringing the
>> entire Apache server down, especially if many users were building their
>> log cache at the same time.
>>
>> To address these problems, it would be great to have a more powerful
>> API, which allows either to retrieve all mergeinfo for a *revision
>> range* or for a *set of revisions*.
>
> The request for a more powerful API certainly makes sense, but what form of
> API?
>
> In the Subversion project source code:
>
> # How many lines/bytes of mergeinfo in trunk, right now?
> $ svn pg -R svn:mergeinfo | wc -lc
> 245 24063
>
> # How many branches and tags?
> $ svn ls ^/subversion/tags/ ^/subversion/branches/ | wc -l
> 288
>
> # Approx. total lines/bytes mergeinfo per revision?
> $ echo $((245 * 289)) $((24063 * 289))
> 70805 6954207
>
> So in each revision there are roughly 70,000 lines of mergeinfo, occupying 7
> MB in plain text representation.
>
> The mergeinfo properties change whenever a merge is done. All other commits
> leave all the mergeinfo unchanged. So mergeinfo is unchanged in, what, 99% of
> revisions?
>
> It doesn't seem logical to simply request all the mergeinfo for each revision
> in turn, and return it all in raw form.
>
> Can we think of a better way to design the API so that it returns the
> interesting data without all the redundancy? Basically I think we want to
> describe changes to mergeinfo, rather than raw mergeinfo.
True, actually on the client-side we interested in the diff, anyway. So
some kind of callback:
interface MergeInfoDiffCallback {
void mergeInfoDiff(int revision, Mergeinfo added, Mergeinfo removed);
}
would be convenient. This would work for revision ranges as well as a
set of revisions.
-Marc
