Item15351: significant performance problem in Foswiki::UI::View

It is very important to remember that the view service needs to be as fast as possible. Therefore any expensive call - i.e. to Foswiki::Meta::getRevisionHistory() - needs to be considered carefully. Under certain circumstances this call can get very expensive, i.e. when using RCSStoreContrib and files have been synced/copied out of band on the filesystem. As a consequence getRevisionHistory() forks an rlog process on each click to count the number of revisions available in the revision control system. The reason for getRevisionHistory() foremost is to render the pseudo macros REVTITLE, REVARG and REVISIONS. These aren't real macros as they only are using during view (and during rdiff using view's local implementation).

Another reason for calling getRevisionHistory() is to compare the requested revision via the ?rev url parameter to the maximum number of available revisions. This check however is redundant as it also happens within the Foswiki::Store and/or Foswiki::Meta api itself. Therefore the call to getRevisionHistoy() can be spared generally and is only required for those PatternSkin-only pseudo macros if present in the skin templates.

-- MichaelDaum - 16 Oct 2024

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