[jira] [Updated] (ARROW-9918) [Rust] [DataFusion] Favor "from" to create arrays

["Jorge (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/ARROW-9918?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Jorge updated ARROW-9918:
-------------------------
    Summary: [Rust] [DataFusion] Favor "from" to create arrays  (was: [Rust] [DataFusion] Move away from builders to create arrays)

> [Rust] [DataFusion] Favor "from" 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
>            Priority: Major
>
> [~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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