adriangb commented on code in PR #20331:
URL: https://github.com/apache/datafusion/pull/20331#discussion_r2852423501
##########
datafusion/physical-expr/src/expressions/dynamic_filters.rs:
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@@ -86,6 +108,11 @@ struct Inner {
/// This is redundant with the watch channel state, but allows us to
return immediately
/// from `wait_complete()` without subscribing if already complete.
is_complete: bool,
+ /// Per-partition filter expressions for partition-index routing.
+ /// When both sides of a hash join preserve their file partitioning (no
RepartitionExec(Hash)),
+ /// build-partition i corresponds to probe-partition i. This allows
storing per-partition
+ /// filters so that each partition only sees its own bounds, giving
tighter filtering.
+ partitioned_exprs: PartitionedFilters,
}
Review Comment:
> In the record batch right before calling `evalute()` on the dynamic filter
expression, we could introduce a new column with the partition index. I think
you already explored this without success, but I would like to understand
better what blockers specifically you faced, I do see this approach yielding a
potential good result.
I also was thinking this approach should work.
Just throwing darts at the wall in terms of helping w/ implementation: you
could create a marker expression e.g. `impl PhysicalExpr for PartitionLiteral`
and then modify the machinery that replaces hive partition values in scans w/
the actual literals to also replace that with the DataFusion partition integer.
https://github.com/apache/datafusion/blob/e937cadbcceff6a42bee2c5fc8d03068fa0eb30c/datafusion/physical-expr-adapter/src/schema_rewriter.rs#L46-L83
https://github.com/apache/datafusion/blob/e937cadbcceff6a42bee2c5fc8d03068fa0eb30c/datafusion/datasource-parquet/src/opener.rs#L217-L261
You'd have to contend with "what if this expression is evaluated without
replacement". I'm not sure when / why that would happen, or if it's okay that
the expression only works in the context of a scan. Maybe just returning null
by default is reasonable behavior.
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