neilconway opened a new pull request, #25723:
URL: https://github.com/apache/datafusion/pull/25723
## Which issue does this PR close?
- N/A
## Rationale for this change
When `IGNORE NULLS` is specified, `array_agg` discards NULLs from its input
by passing a "keep" bitmap to the `filter` kernel. The distinct and ordered
`array_agg` accumulators built this keep bitmap bit-by-bit, by iterating over
the input's logical null buffer. That is inefficient: we can just use the null
buffer as-is. The plain `array_agg` accumulator already did just that.
Benchmarks: `distinct_array_agg` benchmark, M4 Max, 8192 rows
- low cardinality: unchanged
- high cardinality: unchanged
- low cardinality, 10% nulls, ignore nulls: 109.5 us -> 102.2 us (6.7%
faster)
- high cardinality, 10% nulls, ignore nulls: 244.0 us -> 236.0 us (3.3%
faster)
## What changes are included in this PR?
* Introduce a shared helper, `non_null_mask`, to return the keep mask
* Use the new helper in the distinct and ordered `array_agg` accumulators
* Extend benchmark to cover `IGNORE NULLS`
## What is the testing strategy for this PR?
Covered by existing tests.
## Are there any user-facing changes?
No.
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