gene-bordegaray commented on code in PR #23184:
URL: https://github.com/apache/datafusion/pull/23184#discussion_r3486639103
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datafusion/physical-expr/src/partitioning.rs:
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@@ -596,17 +642,39 @@ pub enum Distribution {
/// Requires children to be distributed in such a way that the same
/// values of the keys end up in the same partition
HashPartitioned(Vec<Arc<dyn PhysicalExpr>>),
+ /// Requires rows with equal values for the given keys to be colocated in
+ /// the same partition, without requiring a specific partitioning
algorithm.
+ ///
+ /// Unlike [`Self::HashPartitioned`], this can be satisfied by non-hash
+ /// partitioning such as range partitioning. A partitioning on a subset of
+ /// these keys can also satisfy this requirement because rows equal on all
+ /// required keys are also equal on any subset.
+ ///
+ /// For multi-input operators, satisfaction alone is not enough: each input
+ /// may satisfy its own key requirement while using incompatible partition
+ /// boundaries. Use [`Partitioning::co_partitioned_with`] before pairing
+ /// partitions by index.
+ KeyPartitioned(Vec<Arc<dyn PhysicalExpr>>),
}
Review Comment:
ya I agree with this long-term 🤔
What do you think about deprecating `HashPartitioned` then Introducing
`KeyPartitioned` and lettting this PR be the first real consumer of it. Then we
don't allow range to satisfy `KeyPartitioned` generally here, and only allow
range to satisfy the distribution in the partitioend join case.
Then in following PRs we slowly add some provate helpers to allow range to
satisfay the `KeyPartitioned` like aggregations, then once its at a reasonable
scope (a good amount of operators are working and tested thoroughly), we and
range to the general `satisfaction()` public method.
Trying to think how to do this incrementally
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