Dandandan commented on code in PR #6679:
URL: https://github.com/apache/arrow-datafusion/pull/6679#discussion_r1233952119
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datafusion/core/src/physical_plan/joins/hash_join.rs:
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@@ -563,16 +563,24 @@ pub fn update_hash(
// insert hashes to key of the hashmap
for (row, hash_value) in hash_values.iter().enumerate() {
let item = hash_map
- .0
+ .map
.get_mut(*hash_value, |(hash, _)| *hash_value == *hash);
- if let Some((_, indices)) = item {
- indices.push((row + offset) as u64);
+ if let Some((_, index)) = item {
+ // Already exists: add index to next array
+ let prev_index = *index;
+ // Store new value inside hashmap
+ *index = (row + offset + 1) as u64;
Review Comment:
> Additions become O(1) by holding the end of the chain, right?
Yes, this way `next[value - 1]` contains the previous value, and the next
value / index can be found in the same way again.
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