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Antoine Pitrou commented on ARROW-3165: --------------------------------------- So it seems that build caching doesn't work well. I posted on the CMake mailing-list: https://cmake.org/pipermail/cmake/2018-September/068177.html It seems that one factor is in-source builds (the {{BUILD_IN_SOURCE}} option to {{ExternalProject_Add}}), which render the source tree "dirty". > [CI] Cache externals accross AppVeyor builds > -------------------------------------------- > > Key: ARROW-3165 > URL: https://issues.apache.org/jira/browse/ARROW-3165 > Project: Apache Arrow > Issue Type: Improvement > Components: C++, Continuous Integration > Reporter: Antoine Pitrou > Priority: Major > > Downloading and building third-party libraries may be consuming a significant > chunk of time in our CI chain. It would be nice to cache third-party build > artifacts accross CI builds, to save time. > Unfortunately I ran accross weird issues (especially on Windows / AppVeyor) > when trying to implement this. I don't plan to waste any more time on this > soon. Attempt at > [https://github.com/apache/arrow/compare/master...pitrou:externals_dir] > Edit: it seems I finally found the issue on Windows: ninja is case-sensitive, > you must be careful to canonicalize paths yourself in custom CMake commands > such as in ExternalProject_Add... -- This message was sent by Atlassian JIRA (v7.6.3#76005)