[FEA] Filter join probe table rows that contain nulls when nulls are not equal

[jrhemstad]

Is your feature request related to a problem? Please describe.

In the hash join implementation, we allow controlling the behavior of whether two null elements are considered equal. If nulls are not equal, then two rows that contain nulls can never be considered equal. We exploit this in the build phase of the hash join by constructing a bitmask from ANDing the bitmasks from all the input columns and using that "row bitmask" to filter out any rows that contain a null element from being inserted into the hash table.

When it comes time to probe the hash table, we do not currently take advantage of this some optimization.

Describe the solution you'd like

When probing the hash map and nulls are considered not equal, we should build bitmask from ANDing all of the bitmasks of the probe table and only probe the map when a row does not contain any nulls.

Additional context

The hash join implementation is currently going a complete refactor to use the cuCollections static_multimap. To support the filtered insert, we added an insert_if function. I think we can also add a retrieve_if function to support the filtered probing.

[jrhemstad]

@jlowe points out that both the hash_join constructor and the "probing" member functions allow specifying the null_equality parameter.

This is problematic as a user could specify contradicting options in the build vs probe. The null_equality should be specified exactly once in the hash_join constructor and then stored for future probing operations.

[jlowe]

Filed #9155 to track separately the potential null_equality parameter mismatch problem in the cudf::hash_join API.

[github-actions]

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[github-actions]

This issue has been labeled inactive-90d due to no recent activity in the past 90 days. Please close this issue if no further response or action is needed. Otherwise, please respond with a comment indicating any updates or changes to the original issue and/or confirm this issue still needs to be addressed.