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https://issues.apache.org/jira/browse/ARROW-12629?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17448143#comment-17448143
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Antoine Pitrou commented on ARROW-12629:
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In both cases (CSV and JSON) this can probably be added to {{ReadOptions}}.
> [C++] Configurable read-ahead in CSV and JSON readers
> -----------------------------------------------------
>
> Key: ARROW-12629
> URL: https://issues.apache.org/jira/browse/ARROW-12629
> Project: Apache Arrow
> Issue Type: Improvement
> Components: C++
> Reporter: Andre Kohn
> Priority: Major
> Labels: good-first-issue
>
> We are compiling Arrow C++ to WebAssembly and ran into the following issue
> with the CSV reader:
> Browsers became very picky about the use of SharedArrayBuffers after the
> events around Spectre and Meltdown.
> As a result, you have to compile Arrow to WebAssembly without threads if you
> don't want to run your website with very strict cross-origin isolation.
> Unfortunately, the CSV reader seems to always spawn a thread for the
> read-ahead in both, the SerialStreamingReader and the SerialTableReader
> independent of whether use_threads is set.
> Right now, this effectively means that you cannot use the CSV (and JSON)
> readers in threadless WebAssembly builds.
>
> [https://github.com/apache/arrow/blob/4363fefe46dc357a9013f0f4bcdc235e1e2e8124/cpp/src/arrow/csv/reader.cc#L839]
> [https://github.com/apache/arrow/blob/4363fefe46dc357a9013f0f4bcdc235e1e2e8124/cpp/src/arrow/csv/reader.cc#L913]
>
>
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