ManManson commented on code in PR #13796:
URL: https://github.com/apache/arrow/pull/13796#discussion_r939505349
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cpp/src/arrow/filesystem/localfs.cc:
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@@ -309,6 +313,202 @@ Result<std::vector<FileInfo>>
LocalFileSystem::GetFileInfo(const FileSelector& s
return results;
}
+namespace {
+
+/// Workhorse for streaming async implementation of `GetFileInfo`
+/// (`GetFileInfoGenerator`).
+///
+/// There are two variants of async discovery functions suported:
+/// 1. `DiscoverPartitionFiles`, which parallelizes traversal of individual
directories
+/// so that each directory results are yielded as a separate
`FileInfoGenerator` via
+/// an underlying `DiscoveryImplIterator`, which delivers items in chunks
(default size
+/// is `kBatchSize == 1K` items).
Review Comment:
If we yield on every new item in the queue, more work will be just wasted on
moving back and forth between IO and CPU threads, AFAIU, so internal chunking
makes perfect sense. Moreover, it's naturally supported by the signature of
`GetFileInfoGenerator`, which is supposed to deliver items in some chunks
(though, without indication of batch sizes).
If consumer wants a flattened view (e.g. `AsyncGenerator<FileInfo>`), it
would want use more primitives from `async_generator.h` anyway.
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