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Posted to issues@arrow.apache.org by "Jorge (Jira)" <ji...@apache.org> on 2020/09/05 07:21:00 UTC
[jira] [Created] (ARROW-9918) [Rust] [DataFusion] Move away from
builders to create arrays
Jorge created ARROW-9918:
----------------------------
Summary: [Rust] [DataFusion] Move away from builders to create arrays
Key: ARROW-9918
URL: https://issues.apache.org/jira/browse/ARROW-9918
Project: Apache Arrow
Issue Type: Improvement
Components: Rust, Rust - DataFusion
Reporter: Jorge
Assignee: Jorge
[~yordan-pavlov] hinted in https://issues.apache.org/jira/browse/ARROW-8908 that there is a performance hit when using array builders.
Indeed, I get about 15% speedup by using {{From}} instead of a builder in DataFusion's math operations, and this number _increases with batch size_, which is detrimental since larger batch sizes leverage SDMI better.
Below, {{sqrt_X_Y}}, X is the log2 of the array's size, Y is log2 of the batch size:
{code:java}
sqrt_20_12 time: [34.422 ms 34.503 ms 34.584 ms]
change: [-16.333% -16.055% -15.806%] (p = 0.00 < 0.05)
Performance has improved.
sqrt_22_12 time: [150.13 ms 150.79 ms 151.42 ms]
change: [-16.281% -15.488% -14.779%] (p = 0.00 < 0.05)
Performance has improved.
sqrt_22_14 time: [151.45 ms 151.68 ms 151.90 ms]
change: [-18.233% -16.919% -15.888%] (p = 0.00 < 0.05)
Performance has improved.
{code}
See how there is no difference between {{sqrt_20_12}} and {{sqrt_22_12}} (same batch size), but a measurable difference between {{sqrt_22_12}} and {{sqrt_22_14}} (different batch size).
This issue proposes that we migrate our datafusion and rust operations from builder-base array construction to a non-builder based, whenever possible.
Most code can be easily migrated to use {{From}} trait, a migration is along the lines of
{code:java}
let mut builder = Float64Builder::new(array.len());
for i in 0..array.len() {
if array.is_null(i) {
builder.append_null()?;
} else {
builder.append_value(array.value(i).$FUNC())?;
}
}
Ok(Arc::new(builder.finish()))
{code}
to
{code:java}
let result: Float64Array = (0..array.len())
.map(|i| {
if array.is_null(i) {
None
} else {
Some(array.value(i).$FUNC())
}
})
.collect::<Vec<Option<f64>>>()
.into();
Ok(Arc::new(result)){code}
and this is even simpler as we do not need to use an extra API (Builder).
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