jonathanc-n opened a new pull request, #16434:
URL: https://github.com/apache/datafusion/pull/16434
## Which issue does this PR close?
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- Closes #16179 .
## Rationale for this change
We can use `u32` indices instead of `u64` indices when there are less than
`u32::MAX` rows when building the hashmap. This acts as a memory optimization
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## What changes are included in this PR?
During `HashJoinExec` we construct the `JoinLeftData` with a `Box<dyn
JoinHashMapType>` choosing between a u32 indice or u64 `JoinHashMap`.
I changed the `JoinHashMapType` to hold the `update_from_iter`,
`get_matched_indice`, and `get_matched_indices_with_limit_offset` and split the
`JoinHashMap` into `JoinHashMapU32` and `JoinHashMapU64`.
I deliberately did not try to expose a generic in the trait, nor did I try
to create a generic on the `JoinHashMap` struct as doing so would lead to many
problems with having to call preceding functions with a generic; doing so is
not possible since we are determining the `JoinHashMapType` during runtime.
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## Are these changes tested?
Yes I added a test for checking the hashmap created using u32 indices.
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