ARROW-11332: [Rust] Use MutableBuffer in take_string instead of Vec #9279
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Dandandan
commented
Jan 20, 2021
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| let offsets = offsets_buffer.typed_data_mut(); | ||
| let mut values = Vec::with_capacity(bytes_offset); | ||
| let mut values = MutableBuffer::new(0); |
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Used to be here bytes_offset but that doesn't make a lot of sense.
The values array could be empty as well (e.g. for empty strings), or have a totally different capacity.
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I think a nice followup for |
alamb
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Jan 22, 2021
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Looks good to me -- thanks @Dandandan !
@jorgecarleitao what do you think?
kszucs
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Jan 25, 2021
This PR changes take string to use `MutableBuffer` to create a byte array directly instead of converting it from a `Vec<u8>`.
There used to be some overhead compared to using a `Vec` and converting it to a buffer afterwards, but the overhead seems to be gone now.
The change seems to be neutral according to benchmarks, giving results within a few %. If there is any remaining overhead in `MutableBufffer` I think we should fix that rather than having some workarounds and inconsistencies with other kernels.
```
take str 512 time: [2.3304 us 2.3358 us 2.3419 us]
change: [-4.4130% -4.0693% -3.7241%] (p = 0.00 < 0.05)
Performance has improved.
Found 3 outliers among 100 measurements (3.00%)
2 (2.00%) high mild
1 (1.00%) high severe
Benchmarking take str 1024: Collecting 100 samples in estimated 5.0198 s (1.1M i take str 1024 time: [4.3583 us 4.3633 us 4.3694 us]
change: [-0.5853% +1.1186% +2.9951%] (p = 0.29 > 0.05)
No change in performance detected.
Found 16 outliers among 100 measurements (16.00%)
3 (3.00%) low severe
6 (6.00%) high mild
7 (7.00%) high severe
Benchmarking take str null indices 512: Collecting 100 samples in estimated 5.00 take str null indices 512
time: [2.4779 us 2.4813 us 2.4844 us]
change: [-2.4765% -2.2000% -1.9437%] (p = 0.00 < 0.05)
Performance has improved.
Found 5 outliers among 100 measurements (5.00%)
3 (3.00%) low mild
2 (2.00%) high mild
Benchmarking take str null indices 1024: Collecting 100 samples in estimated 5.0 take str null indices 1024
time: [4.4823 us 4.4910 us 4.5053 us]
change: [-4.8482% -4.5426% -4.2894%] (p = 0.00 < 0.05)
Performance has improved.
Found 5 outliers among 100 measurements (5.00%)
1 (1.00%) low mild
3 (3.00%) high mild
1 (1.00%) high severe
Benchmarking take str null values 1024: Collecting 100 samples in estimated 5.00 take str null values 1024
time: [4.4856 us 4.4889 us 4.4920 us]
change: [-2.2093% -2.0471% -1.8925%] (p = 0.00 < 0.05)
Performance has improved.
Found 7 outliers among 100 measurements (7.00%)
2 (2.00%) low severe
3 (3.00%) low mild
1 (1.00%) high mild
1 (1.00%) high severe
Benchmarking take str null values null indices 1024: Collecting 100 samples in e take str null values null indices 1024
time: [9.6438 us 9.6514 us 9.6592 us]
change: [-2.8600% -2.7478% -2.6338%] (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
```
Closes #9279 from Dandandan/take_string_opt
Authored-by: Heres, Daniel <[email protected]>
Signed-off-by: Andrew Lamb <[email protected]>
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This PR changes take string to use
MutableBufferto create a byte array directly instead of converting it from aVec<u8>.There used to be some overhead compared to using a
Vecand converting it to a buffer afterwards, but the overhead seems to be gone now.The change seems to be neutral according to benchmarks, giving results within a few %. If there is any remaining overhead in
MutableBuffferI think we should fix that rather than having some workarounds and inconsistencies with other kernels.