tustvold commented on a change in pull request #1248:
URL: https://github.com/apache/arrow-rs/pull/1248#discussion_r800229172
##########
File path: arrow/src/compute/kernels/filter.rs
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@@ -185,79 +287,585 @@ pub fn prep_null_mask_filter(filter: &BooleanArray) ->
BooleanArray {
/// # Ok(())
/// # }
/// ```
-pub fn filter(array: &dyn Array, predicate: &BooleanArray) -> Result<ArrayRef>
{
- if predicate.null_count() > 0 {
- // this greatly simplifies subsequent filtering code
- // now we only have a boolean mask to deal with
- let predicate = prep_null_mask_filter(predicate);
- return filter(array, &predicate);
+pub fn filter(values: &dyn Array, predicate: &BooleanArray) ->
Result<ArrayRef> {
Review comment:
Definitely something to measure. I think it would be hard to beat a
strategy that materializes very selective predicates and otherwise just
evaluates predicates against already "eliminated" rows. A masked comparison
kernel, I'd expect to have non-trivial branching overheads, but I honestly
don't know :smile: I guess it also depends on how expensive the predicate is to
evaluate, a complex cast might tip the scales... :thinking:
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