Fix string view LIKE checks with NULL values #6662
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cc @goldmedal |
alamb
reviewed
Nov 1, 2024
arrow-string/src/predicate.rs
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| .map(|haystack| finder.find(haystack).is_some() != negate) | ||
| .enumerate() | ||
| .map(|(idx, haystack)| { | ||
| if nulls.as_ref().map(|n| n.is_null(idx)).unwrap_or_default() { |
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my concern with this approach is that it adds code to the inner loop of the kernel.
We should definitely run benchmarks on this PR before merging
I think another way to solve this would be to either:
- Have two loops -- one when
nullswasSomeand the other whennullswasNone(so we aren't checking each row) - Leave the computation as is (don't check for nulls on the input) but instead simply copy the
Nullsarray from the input to the output (so any input that wasnullwould also benullin the output)
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FWIW I am not sure why this isn't using from_unary like the other codepaths which would provide option 2, and be significantly more efficient than first collecting into a Vec...
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For now i am more concerned about correctness. Producing fast but wrong results isn't as useful.
i changed contains to to use from_unary, that seemed trivially good.
@tustvold might this be it doesn't use from_unary because it wants to use prefix_bytes_iter and suffix_bytes_iter? Please advise! I think we can switch all operations to from_unary to fix correctness and leave tuning performance to a follow-up.
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I am running some benchmarks to see what, if any, impact this has in performance
cargo bench --bench comparison_kernels -- likeI will report back shortly
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ilike_utf8 scalar complex 1.00 2.7±0.05ms ? ?/sec 1.03 2.8±0.09ms ? ?/sec
ilike_utf8 scalar contains 1.01 4.2±0.05ms ? ?/sec 1.00 4.2±0.07ms ? ?/sec
ilike_utf8 scalar ends with 1.02 1279.8±38.11µs ? ?/sec 1.00 1258.4±37.50µs ? ?/sec
ilike_utf8 scalar equals 1.03 801.1±23.96µs ? ?/sec 1.00 775.4±20.05µs ? ?/sec
ilike_utf8 scalar starts with 1.00 1165.9±38.61µs ? ?/sec 1.02 1193.0±54.84µs ? ?/sec
ilike_utf8_scalar_dyn dictionary[10] string[4]) 1.00 77.7±0.09µs ? ?/sec 1.00 77.6±0.07µs ? ?/sec
like_utf8 scalar complex 1.00 1924.8±43.83µs ? ?/sec 1.00 1924.7±49.77µs ? ?/sec
like_utf8 scalar contains 1.00 1562.1±14.30µs ? ?/sec 1.00 1567.9±23.23µs ? ?/sec
like_utf8 scalar ends with 1.02 432.7±11.70µs ? ?/sec 1.00 425.2±5.10µs ? ?/sec
like_utf8 scalar equals 1.16 127.0±0.17µs ? ?/sec 1.00 109.6±0.20µs ? ?/sec
like_utf8 scalar starts with 1.00 339.2±4.42µs ? ?/sec 1.02 347.4±15.72µs ? ?/sec
like_utf8_scalar_dyn dictionary[10] string[4]) 1.00 77.6±0.20µs ? ?/sec 1.00 77.4±0.12µs ? ?/sec
like_utf8view scalar complex 1.00 182.8±0.58ms ? ?/sec 1.01 184.9±0.67ms ? ?/sec
like_utf8view scalar contains 1.02 141.3±0.34ms ? ?/sec 1.00 138.2±0.32ms ? ?/sec
like_utf8view scalar ends with 13 bytes 1.49 66.4±0.42ms ? ?/sec 1.00 44.7±0.27ms ? ?/sec
like_utf8view scalar ends with 4 bytes 1.45 66.1±0.33ms ? ?/sec 1.00 45.4±0.35ms ? ?/sec
like_utf8view scalar ends with 6 bytes 1.46 66.0±0.35ms ? ?/sec 1.00 45.2±0.32ms ? ?/sec
like_utf8view scalar equals 1.00 33.9±0.12ms ? ?/sec 1.11 37.8±0.10ms ? ?/sec
like_utf8view scalar starts with 13 bytes 1.55 68.6±0.36ms ? ?/sec 1.00 44.2±0.33ms ? ?/sec
like_utf8view scalar starts with 4 bytes 1.57 42.6±0.18ms ? ?/sec 1.00 27.2±0.13ms ? ?/sec
like_utf8view scalar starts with 6 bytes 1.53 69.0±0.32ms ? ?/sec 1.00 45.2±0.28ms ? ?/sec
nilike_utf8 scalar complex 1.00 2.7±0.07ms ? ?/sec 1.00 2.7±0.06ms ? ?/sec
nilike_utf8 scalar contains 1.02 4.2±0.05ms ? ?/sec 1.00 4.1±0.05ms ? ?/sec
nilike_utf8 scalar ends with 1.01 1259.7±41.60µs ? ?/sec 1.00 1247.7±26.01µs ? ?/sec
nilike_utf8 scalar equals 1.05 801.3±25.80µs ? ?/sec 1.00 765.8±17.79µs ? ?/sec
nilike_utf8 scalar starts with 1.02 1171.4±33.96µs ? ?/sec 1.00 1146.6±33.64µs ? ?/sec
nlike_utf8 scalar complex 1.00 1918.4±31.09µs ? ?/sec 1.00 1924.4±43.22µs ? ?/sec
nlike_utf8 scalar contains 1.00 1566.2±19.53µs ? ?/sec 1.00 1566.7±16.01µs ? ?/sec
nlike_utf8 scalar ends with 1.00 428.5±5.39µs ? ?/sec 1.02 438.5±14.26µs ? ?/sec
nlike_utf8 scalar equals 1.16 127.0±0.15µs ? ?/sec 1.00 109.5±0.12µs ? ?/sec
nlike_utf8 scalar starts with 1.07 359.3±21.26µs ? ?/sec 1.00 337.2±4.81µs ? ?/sec
It looks like there are some non trivial regressions (50%) or utf8view with scalar starts/ends.
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I did run benchmarks locally too. Thanks @alamb for the instructions.
First, on the commit 1621350 where the PR branch starts
git checkout
16213501769371c7d2d6ce299755337b6db4d8fd
caffeinate -ds cargo bench --bench comparison_kernels -- --save-baseline main like
then on 1e82884, the tip of the PR branch
git checkout findepi/fix-string-view-like-checks-with-null-values-1121b8
caffeinate -ds cargo bench --bench comparison_kernels -- --baseline main like
This command runs bechmark and produces comparison. Let me omit low changes (below 9%) for brevity, as well as outliers reporting.
significant performance regressions:
like_utf8view scalar ends with 4 bytes
time: [36.885 ms 36.925 ms 36.972 ms]
change: [+77.568% +77.857% +78.161%] (p = 0.00 < 0.05)
Performance has regressed.
like_utf8view scalar ends with 6 bytes
time: [36.761 ms 36.818 ms 36.881 ms]
change: [+77.369% +77.776% +78.195%] (p = 0.00 < 0.05)
Performance has regressed.
like_utf8view scalar ends with 13 bytes
time: [36.537 ms 36.613 ms 36.694 ms]
change: [+78.308% +79.019% +79.752%] (p = 0.00 < 0.05)
Performance has regressed.
like_utf8view scalar starts with 4 bytes
time: [25.490 ms 25.542 ms 25.596 ms]
change: [+112.76% +113.25% +113.76%] (p = 0.00 < 0.05)
Performance has regressed.
like_utf8view scalar starts with 6 bytes
time: [36.556 ms 36.598 ms 36.645 ms]
change: [+84.943% +85.578% +86.205%] (p = 0.00 < 0.05)
Performance has regressed.
like_utf8view scalar starts with 13 bytes
time: [37.065 ms 37.105 ms 37.152 ms]
change: [+86.735% +87.424% +88.116%] (p = 0.00 < 0.05)
Performance has regressed.
significant performance improvements:
ilike_utf8 scalar equals
time: [475.56 µs 476.17 µs 476.93 µs]
change: [-47.498% -47.406% -47.310%] (p = 0.00 < 0.05)
Performance has improved.
ilike_utf8 scalar contains
time: [2.4461 ms 2.4500 ms 2.4552 ms]
change: [-15.221% -15.008% -14.786%] (p = 0.00 < 0.05)
Performance has improved.
ilike_utf8 scalar ends with
time: [546.82 µs 547.76 µs 548.86 µs]
change: [-43.736% -43.605% -43.466%] (p = 0.00 < 0.05)
Performance has improved.
ilike_utf8 scalar starts with
time: [560.40 µs 561.46 µs 562.67 µs]
change: [-43.349% -42.997% -42.641%] (p = 0.00 < 0.05)
Performance has improved.
Benchmarking ilike_utf8 scalar complex: Warming up for 3.0000 s
Warning: Unable to complete 100 samples in 5.0s. You may wish to increase target time to 5.4s, enable flat sampling, or reduce sample count to 60.
ilike_utf8 scalar complex
time: [1.0629 ms 1.0637 ms 1.0649 ms]
change: [-29.556% -29.299% -29.062%] (p = 0.00 < 0.05)
Performance has improved.
nilike_utf8 scalar equals
time: [475.34 µs 476.23 µs 477.67 µs]
change: [-46.418% -46.259% -46.081%] (p = 0.00 < 0.05)
Performance has improved.
nilike_utf8 scalar contains
time: [2.4427 ms 2.4449 ms 2.4477 ms]
change: [-15.899% -15.421% -15.120%] (p = 0.00 < 0.05)
Performance has improved.
nilike_utf8 scalar ends with
time: [548.31 µs 548.96 µs 549.63 µs]
change: [-42.924% -42.742% -42.554%] (p = 0.00 < 0.05)
Performance has improved.
nilike_utf8 scalar starts with
time: [557.88 µs 558.54 µs 559.35 µs]
change: [-42.683% -42.392% -42.144%] (p = 0.00 < 0.05)
Performance has improved.
Benchmarking nilike_utf8 scalar complex: Warming up for 3.0000 s
Warning: Unable to complete 100 samples in 5.0s. You may wish to increase target time to 5.4s, enable flat sampling, or reduce sample count to 60.
nilike_utf8 scalar complex
time: [1.0648 ms 1.0669 ms 1.0696 ms]
change: [-28.834% -28.600% -28.353%] (p = 0.00 < 0.05)
Performance has improved.
TL;DR
i must be doing something wrong here. the benchmarks report improvement for code path i didn't change.
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the results are apparently repeatable on my laptop
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okay, easy to fix, actually
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pushed performance-oriented changes
i still observe a regression for one case
like_utf8view scalar starts with 4 bytes
time: [12.899 ms 12.939 ms 12.986 ms]
change: [+7.7003% +8.0298% +8.4320%] (p = 0.00 < 0.05)
Performance has regressed.
and still see improvements for many ilike cases e.g.
nilike_utf8 scalar ends with
time: [547.64 µs 548.55 µs 549.63 µs]
change: [-42.656% -42.257% -41.801%] (p = 0.00 < 0.05)
Performance has improved.
i don't think i know how to move it further from here. @alamb @tustvold ptal
from_unary takes care of nulls
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alamb
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Nov 8, 2024
| @@ -146,6 +138,7 @@ impl<'a> Predicate<'a> { | |||
| } | |||
| Predicate::IStartsWithAscii(v) => { | |||
| if let Some(string_view_array) = array.as_any().downcast_ref::<StringViewArray>() { | |||
| // TODO respect null buffer | |||
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These are good todos -- I will file a ticket to handle them
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i plan to take care of this -- for apache/datafusion#12637
|
Here are my benchmark results. My conclusion is that there is some non trivial variability in the benchmarks but I don't think this PR does anything substantial |
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Nov 14, 2024
* Fix string view LIKE checks with NULL values * Add TODO comments to operations yet to be fixed * Use from_unary for contains with string view from_unary takes care of nulls * Fix performance * fixup! Fix performance
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Which issue does this PR close?
Rationale for this change
Fix correctness
What changes are included in this PR?
Fix
StringView LIKE ..result when tested values include nulls.Are there any user-facing changes?
Yes