exchange: remove one layer of boxing #456
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We were previously forced to use a boxed trait object because we were unable to name the type of the constructed closure. This patch fixes it by introducing a custom `ParallelizationHasher` trait that the `ParallelizationContractCore` expects with a blanket implementation for all closures taking two arguments. This is to maintain backwards compatibility with any code that passes a closure directly to `ExchangeCore::new`. Then a wrapper type `DataHasher<F>` is introduced that allows us to both specialize the `ParallelizationHasher` implementation for single argument closures and at the same time name the type which is what we need to remove one layer of boxed trait objects. Signed-off-by: Petros Angelatos <petrosagg@gmail.com>
Signed-off-by: Petros Angelatos <petrosagg@gmail.com>
antiguru
approved these changes
Mar 17, 2022
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We were previously forced to use a boxed trait object because we were unable to name the type of the constructed closure.
This patch fixes it by introducing a customParallelizationHashertrait that theParallelizationContractCoreexpects with a blanket implementation for all closures taking two arguments. This is to maintain backwards compatibility with any code thatpasses a closure directly toExchangeCore::new.Then a wrapper typeDataHasher<F>is introduced that allows us to both specialize theParallelizationHasherimplementation for single argument closures and at the same time name the type which is what we need to remove one layer of boxed trait objects.UPDATE: After discussion with @frankmcsherry and @antiguru it turns out that we'd rather remove the ability to distribute records based on time, which makes it even easier to remove the box. This PR is now changed to reflect that.