ARROW-11354: [Rust] Speed-up cast of dates and times (2-4x)

[jorgecarleitao]

This PR improves the performance of certain time / date casts by using the brand new API proposed in #9235 .

That API allows for a very fast execution of unary and infalible operations on primitive arrays, and this PR leverages that for cast operations that require a simple mathematical operation.

Switched to branch 'fast_unary'
Compiling arrow v3.0.0-SNAPSHOT (/Users/jorgecarleitao/projects/arrow/rust/arrow)
Finished bench [optimized] target(s) in 1m 06s
Running /Users/jorgecarleitao/projects/arrow/rust/target/release/deps/cast_kernels-25ee76597a8b997b
Gnuplot not found, using plotters backend
cast date64 to date32 512 time: [1.1668 us 1.1706 us 1.1749 us]
change: [-83.347% -83.248% -83.144%] (p = 0.00 < 0.05)
Performance has improved.
Found 5 outliers among 100 measurements (5.00%)
3 (3.00%) high mild
2 (2.00%) high severe
cast date32 to date64 512 time: [899.73 ns 930.58 ns 971.56 ns]
change: [-86.799% -86.520% -86.190%] (p = 0.00 < 0.05)
Performance has improved.
Found 10 outliers among 100 measurements (10.00%)
3 (3.00%) high mild
7 (7.00%) high severe
cast time32s to time32ms 512 time: [728.73 ns 732.33 ns 735.90 ns]
change: [-54.503% -54.201% -53.917%] (p = 0.00 < 0.05)
Performance has improved.
Found 2 outliers among 100 measurements (2.00%)
1 (1.00%) high mild
1 (1.00%) high severe
cast time64ns to time32s 512 time: [4.8374 us 4.8447 us 4.8526 us]
change: [-57.022% -56.791% -56.587%] (p = 0.00 < 0.05)
Performance has improved.
Found 8 outliers among 100 measurements (8.00%)
6 (6.00%) high mild
2 (2.00%) high severe

[github-actions]

https://issues.apache.org/jira/browse/ARROW-11354

[codecov-io]

Codecov Report

Merging #9297 (f88847c) into master (437c8c9) will increase coverage by 0.00%.
The diff coverage is 97.36%.

@@ Coverage Diff @@## master #9297 +/- ##
=======================================
Coverage 81.88% 81.89% =======================================
Files 215 216 +1 Lines 52988 52983 -5 =======================================
- Hits 43391 43388 -3 + Misses 9597 9595 -2 

Impacted Files	Coverage Δ
rust/arrow/src/compute/kernels/arity.rs	91.66% <91.66%> (ø)
rust/arrow/src/compute/kernels/cast.rs	97.08% <100.00%> (+0.09%)	⬆️
rust/parquet/src/encodings/encoding.rs	95.43% <0.00%> (+0.19%)	⬆️

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[jorgecarleitao]

NOTE: this PR is 40 LOC change. The rest comes from the other PR. Please wait for the merge, this is only a draft to indicate what can be done with this.

[nevi-me]

Thanks for generalising this, and cleaning up the cast kernels. There were plenty of fruits hanging low there.

[nevi-me]

We could save a further few cycles here by specifying the null count, as it's known and trusted to be correct.

[nevi-me]

This is a great and simple example, and I wonder if the compiler is smart enough to optimise 2 commutative unary functions to perform as well as a single combined one.

Worth trying out some time.

[nevi-me]

Should we call this something more general, like arityhttps://en.wikipedia.org/wiki/Arity

We'd probably want a binary function that takes 2 arguments, or maybe ternary if we're feeling cute enough to push it 😉.

EDIT: math_op is binary

[jorgecarleitao]

Since this was only unary, I gave it that name. Note that we can lift all binary arithmetics into a generic like this one and place it together.

I do not have strong feelings here, but it is the first time I hear about arity xD

[nevi-me]

No worries, whoever adds a ternary function can change the name.

[jorgecarleitao]

That would be backward incompatible, so it would be good to change it soon. I will change to arity. It is a fun name. Another option would be generics, but that is too generic. :)