Apply BroadcastMode key projections before interpreting key expressions in subqueries [databricks] #6268
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…ns in subqueries Signed-off-by: Jason Lowe <jlowe@nvidia.com>
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Fixes #6232. When the GPU broadcasts for a hash join, it does not broadcast a hash table like the CPU does, rather it just broadcasts the original build table. This is normally fine, but it can cause problems in DPP/subquery usage where the planning assumes that the HashedRelation key expressions have already been applied to the broadcasted data. In the GPU case this has not happened, and thus those expressions can be critical to proper interpretation of the broadcast data. #6232 shows a query where the HashedRelation keys are rearranging the original data, and failure to evaluate those expressions results in the wrong column being used in the subquery exec.
To fix it, we grab any expressions found on the BroadcastMode and evaluate them in the GpuSubqueryExec before trying to apply the normal BoundReference projection to extract the desired key.