[GitHub] [arrow-datafusion] Dandandan commented on issue #50: Vectorize hash join collision check

["Dandandan (via GitHub)" <gi...@apache.org>]

Dandandan commented on issue #50:
URL: https://github.com/apache/arrow-datafusion/issues/50#issuecomment-1597373205

   FYI @metesynnada I'm working on a prototype.
   
   Translated the code out of https://dare.uva.nl/search?identifier=5ccbb60a-38b8-4eeb-858a-e7735dd37487 to this, which seems roughly equivalent:
   
   ```rust
       let mut to_check: Vec<(u64, usize)> = hash_values
           .iter()
           .enumerate()
           .flat_map(|(row, hash_value)| {
               build_hashmap
                   .map
                   .get(*hash_value, |(hash, _)| *hash_value == *hash)
                   .map(|(_, v)| (*v - 1, row))
           })
           .collect();
   
       while to_check.len() > 0 {
           // Perform column-wise (vectorized) equality check
   
           // check next items
           to_check = to_check
               .iter()
               .flat_map(|(index, row)| {
                   let next = build_hashmap.next[*index as usize];
                   (next != 0).then(|| (next - 1, *row))
               })
               .collect();
       }
   ```
   
   
   


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