A customer recently asked us why we prefer using labels in Perforce. We recommend revision-tagged labels as they don't have the performance issues associated with classic file-tagged labels at large Perforce sites (they are more than 100x faster to use in common operations).
The following is a discussion with Tom Tyler, Go2Group's resident Perforce expert.
Q: What is the difference between tagging a set of files and labeling a set of files?A: There really is no difference. Tagging and labeling are different ways of saying the same thing - in fact, tagging a set of files is a good definition for labeling.
Q: What if a user wants an exact revision number except one file is much older?A: That sort of flexibility is possible with the old, file-tagged labels. With file-tagged labels, you can set the label down on any arbitrary set of files and any arbitrary set of revisions of the selected files.
With revision-tagged labels, you can set the label down on an arbitrary set of files, but the revision specifier for the label applies to all specified files.
Using only revision-tagged labels is preferred. If you get into a case where you want to refer to all new files and just one or an old revision, we would recommend just submitting rolling back those files, submitting a new version of the file that has the same contents as the old version needed. The result is a single changelist that defines all the files wanted – much easier reproducibility. After you fire off your build, you can roll the files forward again if needed.
Q: With is the difference in tagging vs. labeling in these cases? A: In this case, the tags = labels. The P4V icon for a label is an old grocery-store tag.
Labels: go2group - tom's column
