Handle DynamicFilters crossing BufferExec nodes #20778

Is your feature request related to a problem or challenge?

#19761 introduced buffering on the probe side of a HashJoinExec node as an optional feature for eagerly fetching the probe side.

While this demonstrates speed in benchmarks, it does not play well with dynamic filters, as the buffering behavior does not let the dynamic filter produce any meaningful filter, therefore, fetching more than whats necessary.

For this reason, hash join buffering on the probe side is an optional feature.

Describe the solution you'd like

It would be nice to detect when a dynamic filter exists below the BufferExec node and either:

• disable the buffering behavior
• hold a reference to the dynamic filter and be smart about whether it's worth waiting for it or not

Describe alternatives you've considered

Just leave the hash join buffering off by default forever

Additional context

No response