Hi, I've filed a PR to activate concurrent test execution by default: https://github.com/apache/calcite/pull/1702
It results in concurrent execution of both methods and classes. Note: it was something that was present in Maven, and now it will be there in Gradle as well. It looks to work on my machine (which is 1s4c8t), however, it might be there are still concurrency issues left. I noticed two major issues: 1) https://github.com/apache/calcite/commit/d32ee5c320938b5c34ce09df2276c9570c27a301#diff-2b9a6c719e7c1c69c76dccbbc1654ae8R2593 That commit added Hook.REL_BUILDER_SIMPLIFY.add(Hook.propertyJ(false)) which was basically a global hook, so that test induced other test failures. 2) [CALCITE-3285] EnumerableMergeJoin should support non-equi join conditions https://github.com/apache/calcite/commit/a0931b784c60683eb6845b3087d79f33160fc868#diff-d746ae553342ceeb0806df4a03e1e51eR44 It added a static field to EnumerableConvention which induced failures in concurrent execution. I've reworked CALCITE-3285 (see PR 1702), and hopefully, it would work better. In the meantime please feel free to try concurrent execution and let me know how that works. Vladimir
