perf: optimize find_in_set in datafusion-functions#23460
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andygrove
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Jul 10, 2026
| // built at most once here rather than per row. | ||
| let map: Option<HashMap<&str, usize>> = | ||
| (str_list.len() >= FIND_IN_SET_LOOKUP_THRESHOLD).then(|| { | ||
| let mut map = HashMap::with_capacity(str_list.len()); |
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This map is reconstructed for each batch being processed. Would be better to reuse across batches.
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I looked into this, and it doesn't seem like it would improve performance much, and would be a significant change.
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Which issue does this PR close?
N/A
Rationale for this change
Improve performance of existing expression.
What changes are included in this PR?
Replace per-row O(set_len) linear scan in find_in_set's constant-list path with a one-time HashMap lookup (threshold-guarded so short lists keep the linear scan), giving O(1) per-row probing for large sets.
Are these changes tested?
Existing tests + new tests
Benchmark (criterion):
Are there any user-facing changes?
No