nuno-faria commented on code in PR #27237: URL: https://github.com/apache/datafusion/pull/27237#discussion_r4517202776
########## datafusion/physical-expr/src/equivalence/grouping.rs: ########## @@ -22,10 +22,38 @@ use datafusion_physical_expr_common::physical_expr::format_physical_expr_list; /// order. Contiguity applies to the complete partition stream, not separately /// to each record batch. /// +/// For example, consider the following table: +/// +/// ```text +/// ┌───┬───┬───┐ +/// │ a │ b │ c │ +/// ├───┼───┼───┤ +/// │ 2 │ 1 │ 5 │ +/// │ 2 │ 1 │ 3 │ +/// │ 1 │ 3 │ 4 │ +/// │ 2 │ 2 │ 1 │ +/// │ 2 │ 2 │ 2 │ +/// └───┴───┴───┘ +/// ``` +/// +/// * Is grouped by `[a, b]`, as rows with the same `(a, b)` are contiguous, +/// even though the table is not sorted by `a`, `b` nor `(a, b)`. +/// * Is grouped by `[b]`, since each value of `b` is in one run. +/// * Is NOT grouped by `[a]`, because `a = 2` appears in two separate runs. +/// Review Comment: Is it also grouped by `c`, `c,a`, ...? 🤔 -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
