rtpsw commented on code in PR #13880:
URL: https://github.com/apache/arrow/pull/13880#discussion_r954269544
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cpp/src/arrow/compute/exec/asof_join_node.cc:
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@@ -294,10 +452,22 @@ class InputState {
// Index of the time col
col_index_t time_col_index_;
// Index of the key col
- col_index_t key_col_index_;
+ vec_col_index_t key_col_index_;
+ // Type id of the time column
+ Type::type time_type_id_;
+ // Type id of the key column
+ std::vector<Type::type> key_type_id_;
+ // Hasher for key elements
+ mutable KeyHasher* key_hasher_;
+ // True if hashing is mandatory
+ bool must_hash_;
+ // True if null by-key values are expected
+ bool nullable_by_key_;
Review Comment:
For performance. There are two code-paths for computing a by-key value:
1. A slower path using hashing, which works for any kind of by-key (single
or multi, of any type)
2. A faster path using
[norm-value](https://github.com/apache/arrow/pull/13880/files#diff-5789a42aebc3bd0f5a6db687c78ab0c3eef3e316982f99fe9e0ea21fabed354cR67),
which works only for a single-primitive-types by-key
We want to use the faster path whenever possible. [This
post](https://github.com/apache/arrow/pull/13880#issuecomment-1225741731)
explains an alternative that would avoid this flag at the expense of runtime
complexity.
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