-
Suggestion
-
Resolution: Fixed
-
None
-
5
-
Bitbucket implements merging of pull requests using git-merge; however as of Git 2.38 an alternative exists, it is now possible to use git-merge-tree and git-commit-tree to achieve the same goal. It would be beneficial to use this new approach for Bitbucket instances running Git 2.38.0 or later.
This will achieve a significant increase in performance since while git-merge needs to read/write the index and working tree, git-merge-tree does need to do this, in fact it can operate on a bare repository. Some experiments I've performed using a huge repository shows a decreasing in merge time from 17s using git-merge in Git 2.37 to 0.1s using git-merge-tree plus git-commit-tree in Git 2.38.
A similar change was previously made in the codepath where Bitbucket determines mergeability of a pull request (try-merge): https://jira.atlassian.com/browse/BSERV-13691
Side note:
Implementing this sooner than later is perhaps important because in Git 2.38 an unrelated bug fix results in an increase in the run time of git-merge: https://github.com/git/git/commit/034195ef927bcfc348a69672494f3781e8f5c093
This bug fix involves adding a step to restore the index and working tree to the pre-merge state. Testing with the same repository above shows an increase in time to run git-merge from 17s with Git 2.37 to 31s with Git 2.38. Furthermore, the peak memory usage was slightly higher in Git 2.38 as a result of the additional save_state step. This bug fix only results in slower git-merge, it does not impact the performance of git-merge-tree since the later does not use the index or working-tree.
| Form Name | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
[BSERV-14066] Implement pull request merge using git-merge-tree and git-commit-tree
This has now been implemented in Bitbucket Data Center 8.18.
Internal testing has shown between a 10x and 100x improvement in times for merges, depending on the size of the repository and the actual merge. Note that merge-tree will only be used if Git 2.38+ is installed on the system.
Seems like a huge benefit and performance gain for our software developers, if coming!
Would be great , if Atlassian can implement it not only in the newest release, but also in 7.21.X , since it will still take some time for us to prepare and upgrade to the newest LTS version.
Thanks
Robby
Nicely spotted, thanks 187981459b6d. And in fact the number was meant to be 31s for Git 2.38.
Thanks for creating this issue.
Just to reduce confusion, I think you have a number typo in your side note:
Should it be:
git-merge from 17s with Git 2.37 to 21s with Git 2.38.
@Kitzinger wolfgang: great news, that this BSERV is getting implemented ( 8.18 ). Does Atlassian also backport this in 8.9.X ?
would be important, as 8.9 is the current LTS version.