Github user zuyu commented on a diff in the pull request:
https://github.com/apache/incubator-quickstep/pull/171#discussion_r98383388
--- Diff: query_optimizer/PhysicalGenerator.cpp ---
@@ -109,6 +114,13 @@ P::PhysicalPtr PhysicalGenerator::optimizePlan() {
} else {
rules.emplace_back(new SwapProbeBuild());
}
+ if (FLAGS_reorder_columns) {
+ // NOTE(jianqiao): This optimization relies on the fact that the
intermediate
+ // relations all have SPLIT_ROW_STORE layouts. If this fact gets
changed, the
+ // optimization algorithm may need to be updated and the performance
impact
+ // should be re-evaluated.
--- End diff --
I suggest to check this assumption in `ReorderColumns::IsTransformable`, so
we could remove this comment here.
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