adriangb commented on code in PR #15566:
URL: https://github.com/apache/datafusion/pull/15566#discussion_r2029889101
##########
datafusion/physical-plan/src/execution_plan.rs:
##########
@@ -467,8 +467,106 @@ pub trait ExecutionPlan: Debug + DisplayAs + Send + Sync {
) -> Result<Option<Arc<dyn ExecutionPlan>>> {
Ok(None)
}
+
+ /// Returns a set of filters that this operator owns but would like to be
pushed down.
+ /// For example, a `TopK` operator may produce dynamic filters that
reference it's currrent state,
+ /// while a `FilterExec` will just hand of the filters it has as is.
+ /// The default implementation returns an empty vector.
+ /// These filters are applied row-by row and any that return `false` or
`NULL` will be
+ /// filtered out and any that return `true` will be kept.
+ /// The expressions returned **must** always return `true` or `false`;
+ /// other truthy or falsy values are not allowed (e.g. `0`, `1`).
+ ///
+ /// # Returns
+ /// A vector of filters that this operator would like to push down.
+ /// These should be treated as the split conjunction of a `WHERE` clause.
+ /// That is, a query such as `WHERE a = 1 AND b = 2` would return two
+ /// filters: `a = 1` and `b = 2`.
+ /// They can always be assembled into a single filter using
+ /// [`split_conjunction`][datafusion_physical_expr::split_conjunction].
+ fn filters_for_pushdown(&self) -> Result<Vec<Arc<dyn PhysicalExpr>>> {
+ Ok(Vec::new())
+ }
+
+ /// Checks which filters this node allows to be pushed down through it
from a parent to a child.
+ /// For example, a `ProjectionExec` node can allow filters that only
refernece
+ /// columns it did not create through but filters that reference columns
it is creating cannot be pushed down any further.
+ /// That is, it only allows some filters through because it changes the
schema of the data.
+ /// Aggregation nodes may not allow any filters to be pushed down as they
change the cardinality of the data.
+ /// RepartitionExec nodes allow all filters to be pushed down as they
don't change the schema or cardinality.
+ fn filter_pushdown_request(
Review Comment:
I tried looking into `try_swapping_with_projection`, it's a bit complicated
but I think it does do the recursion internally which won't work for us as
discussed previously / that's why we made this an optimizer rule:
https://github.com/apache/datafusion/blob/e15374f9d4e47f305259447f50ac725fa5a35358/datafusion/datasource/src/memory.rs#L132
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