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https://issues.apache.org/jira/browse/ARROW-16117?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Dominik Moritz resolved ARROW-16117.
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Fix Version/s: 8.0.0
Resolution: Fixed
Issue resolved by pull request 12793
[https://github.com/apache/arrow/pull/12793]
> [JS] Improve UTF8 decoding performance
> --------------------------------------
>
> Key: ARROW-16117
> URL: https://issues.apache.org/jira/browse/ARROW-16117
> Project: Apache Arrow
> Issue Type: Improvement
> Components: JavaScript
> Environment: MacOS, Chrome, Safari
> Reporter: Howard Zuo
> Assignee: Dominik Moritz
> Priority: Major
> Labels: pull-request-available
> Fix For: 8.0.0
>
> Time Spent: 2.5h
> Remaining Estimate: 0h
>
> While profiling the performance of decoding TPC-H Customer and Part
> in-browser, datasets where there are a lot of UTF8s, it turned out that much
> of the time was being spent in {{getVariableWidthBytes}} rather than in
> {{TextDecoder}} itself. Ideally all the time should be spent in
> {{{}TextDecoder{}}}.
> On Chrome {{getVariableWidthBytes}} took up to ~15% of the e2e decoding
> latency, and on Safari it was close to ~40% (Safari's TextDecoder is much
> faster than Chrome's, so this took up relatively more time).
> This is likely because the code in this PR is more amenable to V8/JSC's JIT,
> since {{x}} and {{y}} now are guaranteed to be SMIs ("small integers")
> instead of Object, allowing the JIT to emit efficient machine instructions
> that only deal in 32-bit integers. Once V8 discovers that a {{x}} and {{y}}
> can potentially be null (upon iterating past the bounds), it "poisons" the
> codepath forever, since it has to deal with the null case.
> See this V8 post for a more in-depth explanation (in particular see the
> examples underneath "Performance tips"):
> [https://v8.dev/blog/elements-kinds]
> Doing the bounds check explicitly instead of implicitly basically eliminates
> this function from showing up in the profiling. Empirically, on my machine
> decoding TPC-H Part dropped from 1.9s to 1.7s on Chrome, and Customer dropped
> from 1.4s to 1.2s.
> [https://github.com/apache/arrow/pull/12793]
>
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