Frequently asked questions

Does QLever run on Windows and MacOS?

The qlever command-line tool uses the official Docker image of QLever by default. Docker runs natively on Linux, with only a small performance penalty. However, on Windows and MacOS, Docker runs inside a virtual machine, which may incur a significant performance penalty. In particular, RAM consumption may be prohibitive. We are working towards binary releases for Windows and MacOS. In the meantime, we strongly recommend using QLever on a Linux machine.

Can QLever read compressed files or multiple files?

Yes, QLever can process multiple input streams produced by arbitrary commands supported by your system. See the options CAT_INPUT_FILES and MULTI_INPUT_FILES in the Qleverfile settings.

My index build runs out of memory, what can I do?

If you have a large input set or a machine with little RAM, you should carefully set STXXL_MEMORY, ULIMIT, and SETTINGS_JSON. See the explanations in the Qleverfile settings.

I have problems or I think I found a bug, what can I do?

Please first search https://github.com/ad-freiburg/qlever/issues, maybe your issue has already been reported or solved. If it has been reported before but is not yet solved, please add a comment to the existing issue. If it has not been reported before, please open a new issue. Please provide as much detail as possible, including the exact command you ran, the content of your Qleverfile (if applicable), and the relevant output. And try to provide a minimal example (in particular, a minimal SPARQL query) that reproduces the issue.

Does QLever have releases?

We currently treat every commit to the master branch as a release. In particular, each commit comes with a detailed description and an own Docker image on https://hub.docker.com/r/adfreiburg/qlever/, tagged with the commit hash as well as with the corresponding pull request number. Each commit is extensively tested and reviewed before being merged into the QLever master.

Are there publications about QLever?

Yes, see the README of https://github.com/ad-freiburg/qlever.