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Bug 357734

Summary: [server][log] Improve the performance of Git Log
Product: [ECD] Orion Reporter: Szymon Brandys <Szymon.Brandys>
Component: GitAssignee: Tomasz Zarna <tomasz.zarna>
Status: RESOLVED FIXED QA Contact:
Severity: normal    
Priority: P3 CC: john.arthorne, mamacdon, simon_kaegi
Version: 0.2   
Target Milestone: 0.5 M1   
Hardware: PC   
OS: Windows XP   
Whiteboard:
Bug Depends on: 343506, 357774, 358214, 370132    
Bug Blocks:    
Attachments:
Description Flags
mylyn/context/zip none

Description Szymon Brandys CLA 2011-09-15 04:10:38 EDT 
Orion Git Log supports pages however the implementation does not perform well and timeouts still may occur. This is because even if we are requesting a page a few commits, the server implementation gets the full log (what takes time) and then just cuts out requested commits and returns them.
Comment 1 Tomasz Zarna CLA 2011-09-15 05:57:20 EDT 
This is not going to be as easy as I initially expected. I was aware that JGit porcelain API for git-log is missing params suitable for paging (the reason why Szymon implemented the logic as described in comment 0), but I hoped we can achieve that by using a lower lever API. Unfortunately, even though CGit git-log has params that are useful here (i.e. --skip and --n) they are not available in JGit. The problem here is that both org.eclipse.jgit.pgm.Log and org.eclipse.jgit.api.LogCommand use RevWalk which walks a commit graph. It's an Iterable so I guess the best approach would be to modify the way it returns commits (eg. by providing a org.eclipse.jgit.revwalk.Generator).
Comment 2 Tomasz Zarna CLA 2011-09-15 12:29:48 EDT 
(In reply to comment #0)
> the server implementation gets the full log (what takes time) 

Creating the walker doesn't seem to be time-consuming, it's the walk itself (i.e. calling next()) that may cause timeouts. Having said that, I was quite surprised hearing that even git-logs with few commits[1] can time out. 

[1] those little git log widgets on the Git Status page
Comment 3 Tomasz Zarna CLA 2011-09-26 08:01:33 EDT 
Another way of improving Git Log is caching the result, see bug 339846.
Comment 4 Tomasz Zarna CLA 2011-10-03 05:02:02 EDT 
Fixing bug 343506 and bug 358214 gave the Git Log enough boost, so we can postpone the other two (ie. bug 339846, bug 357774) until 0.4.
Comment 5 Tomasz Zarna CLA 2012-01-09 07:55:35 EST 
Fixed with f94cba36c46d09f0471491a549390231c11011ee and new options for LogCommand (see bug 357774).
Comment 6 Tomasz Zarna CLA 2012-01-09 07:55:55 EST 
Created attachment 209201 [details]
mylyn/context/zip
Comment 7 Tomasz Zarna CLA 2012-02-02 08:13:21 EST 
I'm reopening this one, waiting for a fix for bug 370132 in JGit. For more details see bug 368567.
Comment 8 Tomasz Zarna CLA 2012-03-22 10:58:40 EDT 
Re-applied the fix from comment 5 as 59ef7185dcc4e8fdb38e0aeb987caa8ddb22a7a7