IN LIST: add branchless filter for small primitive lists

[geoffreyclaude]

Which issue does this PR close?

• Part of Further improve performance of IN list evaluation #19241.
• Stacked on #23311.
• Next in stack: IN LIST: add direct-probe hash filter for large primitive lists #23015.
• Extracted from Optimize IN performance with specialized implementations #19390.

Rationale for this change

For very small IN lists, building or probing a hash table can be more work than just comparing the input value with each constant.

For example, for x IN (10, 20, 30), the fast path can behave like:

x == 10 OR x == 20 OR x == 30

Because the list is tiny, those comparisons are cheap. The implementation stores the constants in a fixed-size array and checks them with a compact comparison chain.

“Branchless” here means the comparisons are combined without stopping at the first match. That can be faster for these small fixed-width lists because the CPU gets a predictable sequence of simple operations instead of hash-table setup and probe logic.

Larger primitive lists are left for #23015, where a purpose-built hash lookup becomes the better tradeoff.

For non-unsigned primitive values, this PR keeps the logical Arrow type explicit and uses the matching unsigned same-width physical representation only inside the branchless filter. For example, Float16 uses UInt16 storage, Float32 uses UInt32 storage, and TimestampNanosecond uses UInt64 storage. This preserves bit-pattern equality while keeping construction and probing tied to the original logical type.

What changes are included in this PR?

• Adds a const-generic BranchlessFilter for small primitive IN lists.
• Adds thresholds for when this path is used:
  • up to 16 values for 1-byte types
  • up to 8 values for 2-byte types
  • up to 32 values for 4-byte types
  • up to 16 values for 8-byte types
• Keeps dispatch concrete and explicit in strategy.rs.
• Maps each optimized non-unsigned logical type to its matching unsigned same-width branchless representation:
  • Int8 -> UInt8
  • Int16, Float16 -> UInt16
  • Int32, Float32, Date32, Time32 -> UInt32
  • Int64, Float64, Date64, Time64, Timestamp, Duration -> UInt64
• Leaves larger 1-byte and 2-byte lists on the existing bitmap filters.
• Leaves larger 4-byte and 8-byte lists on the existing hash/generic paths.
• Leaves 16-byte, decimal, and interval types on the generic path.
• Keeps the same IN / NOT IN null behavior as the rest of the stack.
• Adds focused coverage for branchless null handling, signed boundary values, slices, Float16/Float32/Float64 bit patterns, and same-width wrong-type probe rejection.

Are these changes tested?

Yes.

• cargo fmt --all -- --check
• cargo test -p datafusion-physical-expr expressions::in_list --lib
• cargo test -p datafusion-physical-expr --bench in_list_strategy --no-run
• cargo clippy --all-targets --all-features -- -D warnings

Are there any user-facing changes?

No. This is an internal performance optimization only.

Local benchmark snapshot

Built and run with release-nonlto, filtered to the relevant small primitive-list rows:

cargo bench -p datafusion-physical-expr --profile release-nonlto --bench in_list_strategy -- <filter> --save-baseline <baseline>

Filters used: narrow_integer, primitive/i32/small_list, primitive/i64/small_list, f32/small_list, and timestamp_ns/small_list.

Method: directly compared Criterion's raw sample minima (min(time / iterations)) from sample.json. Lower is better; changes within +/-5% are treated as noise.

Compared baselines: #23311 -> #23014

Relevant scope: small primitive-list rows.

Summary: 37 relevant rows, 26 faster, 0 slower, 11 within +/-5%.

Largest relevant deltas:

Benchmark	Before	After	Change
timestamp_ns/small_list/list=4/match=50%	46.55 us	3.17 us	-93.2% (14.69x faster)
f32/small_list/list=4/match=50%	33.93 us	3.04 us	-91.0% (11.15x faster)
primitive/i32/small_list/list=4/match=50%	32.63 us	3.08 us	-90.5% (10.58x faster)
primitive/i64/small_list/list=4/match=50%	33.55 us	3.18 us	-90.5% (10.54x faster)
timestamp_ns/small_list/list=4/match=0%	19.57 us	3.18 us	-83.8% (6.16x faster)
f32/small_list/list=4/match=0%	18.14 us	3.05 us	-83.2% (5.95x faster)
primitive/i32/small_list/list=4/match=0%	17.00 us	3.04 us	-82.1% (5.59x faster)
primitive/i64/small_list/list=4/match=0%	17.12 us	3.22 us	-81.2% (5.31x faster)
primitive/i32/small_list/list=16/match=50%/NOT_IN	31.98 us	7.26 us	-77.3% (4.41x faster)
nulls/primitive/i32/small_list/list=16/match=50%/nulls=20%	29.35 us	7.32 us	-75.1% (4.01x faster)
timestamp_ns/small_list/list=16/match=50%	45.32 us	11.79 us	-74.0% (3.84x faster)
nulls/primitive/i32/small_list/list=16/match=50%/nulls=50%	25.89 us	7.31 us	-71.8% (3.54x faster)
nulls/primitive/i32/small_list/list=16/match=50%/nulls=20%/NOT_IN	26.05 us	7.42 us	-71.5% (3.51x faster)
f32/small_list/list=32/match=50%	38.78 us	13.27 us	-65.8% (2.92x faster)
primitive/i64/small_list/list=16/match=50%	29.46 us	11.76 us	-60.1% (2.50x faster)

Full relevant table (37 rows)

Benchmark	Before	After	Change
narrow_integer/u8/list=4/match=0%	3.86 us	2.79 us	-27.8% (1.38x faster)
narrow_integer/u8/list=4/match=50%	3.84 us	2.78 us	-27.7% (1.38x faster)
narrow_integer/u8/list=16/match=0%	3.88 us	3.85 us	-0.8% (within noise)
narrow_integer/u8/list=16/match=50%	3.84 us	3.86 us	+0.5% (within noise)
narrow_integer/i16/list=4/match=0%	3.93 us	3.18 us	-19.1% (1.24x faster)
narrow_integer/i16/list=4/match=50%	3.92 us	3.16 us	-19.5% (1.24x faster)
narrow_integer/i16/list=64/match=0%	3.96 us	3.82 us	-3.5% (within noise)
narrow_integer/i16/list=64/match=50%	3.91 us	3.80 us	-2.9% (within noise)
narrow_integer/i16/list=256/match=0%	3.90 us	3.81 us	-2.5% (within noise)
narrow_integer/i16/list=256/match=50%	3.97 us	3.81 us	-4.1% (within noise)
narrow_integer/f16/list=4/match=0%	3.87 us	3.16 us	-18.5% (1.23x faster)
narrow_integer/f16/list=4/match=50%	3.94 us	3.15 us	-20.2% (1.25x faster)
narrow_integer/f16/list=64/match=0%	3.87 us	3.84 us	-0.6% (within noise)
narrow_integer/f16/list=64/match=50%	3.93 us	3.85 us	-1.9% (within noise)
narrow_integer/f16/list=256/match=0%	3.90 us	3.84 us	-1.5% (within noise)
narrow_integer/f16/list=256/match=50%	3.87 us	3.91 us	+1.2% (within noise)
nulls/narrow_integer/u8/list=16/match=50%/nulls=20%	3.92 us	4.02 us	+2.5% (within noise)
primitive/i32/small_list/list=4/match=0%	17.00 us	3.04 us	-82.1% (5.59x faster)
primitive/i32/small_list/list=4/match=50%	32.63 us	3.08 us	-90.5% (10.58x faster)
primitive/i32/small_list/list=32/match=0%	16.34 us	13.33 us	-18.5% (1.23x faster)
primitive/i32/small_list/list=32/match=50%	31.17 us	13.31 us	-57.3% (2.34x faster)
primitive/i32/small_list/list=16/match=50%/NOT_IN	31.98 us	7.26 us	-77.3% (4.41x faster)
nulls/primitive/i32/small_list/list=16/match=50%/nulls=20%	29.35 us	7.32 us	-75.1% (4.01x faster)
nulls/primitive/i32/small_list/list=16/match=50%/nulls=20%/NOT_IN	26.05 us	7.42 us	-71.5% (3.51x faster)
nulls/primitive/i32/small_list/list=16/match=50%/nulls=50%	25.89 us	7.31 us	-71.8% (3.54x faster)
primitive/i64/small_list/list=4/match=0%	17.12 us	3.22 us	-81.2% (5.31x faster)
primitive/i64/small_list/list=4/match=50%	33.55 us	3.18 us	-90.5% (10.54x faster)
primitive/i64/small_list/list=16/match=0%	16.34 us	11.93 us	-27.0% (1.37x faster)
primitive/i64/small_list/list=16/match=50%	29.46 us	11.76 us	-60.1% (2.50x faster)
f32/small_list/list=4/match=0%	18.14 us	3.05 us	-83.2% (5.95x faster)
f32/small_list/list=4/match=50%	33.93 us	3.04 us	-91.0% (11.15x faster)
f32/small_list/list=32/match=0%	22.05 us	13.43 us	-39.1% (1.64x faster)
f32/small_list/list=32/match=50%	38.78 us	13.27 us	-65.8% (2.92x faster)
timestamp_ns/small_list/list=4/match=0%	19.57 us	3.18 us	-83.8% (6.16x faster)
timestamp_ns/small_list/list=4/match=50%	46.55 us	3.17 us	-93.2% (14.69x faster)
timestamp_ns/small_list/list=16/match=0%	19.73 us	12.07 us	-38.8% (1.63x faster)
timestamp_ns/small_list/list=16/match=50%	45.32 us	11.79 us	-74.0% (3.84x faster)