[GitHub] [arrow] pitrou commented on a change in pull request #8101: ARROW-9868: [C++][R] Provide CopyFiles for copying files between FileSystems

[GitBox <gi...@apache.org>]

pitrou commented on a change in pull request #8101:
URL: https://github.com/apache/arrow/pull/8101#discussion_r482921231



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File path: cpp/src/arrow/filesystem/filesystem.cc
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@@ -439,6 +440,28 @@ Result<std::shared_ptr<io::OutputStream>> SlowFileSystem::OpenAppendStream(
   return base_fs_->OpenAppendStream(path);
 }
 
+Status CopyFiles(const std::shared_ptr<FileSystem>& src_fs,
+                 const std::vector<std::string>& src_paths,
+                 const std::shared_ptr<FileSystem>& dest_fs,
+                 const std::vector<std::string>& dest_paths, int64_t chunk_size,
+                 bool use_threads) {
+  if (src_paths.size() != dest_paths.size()) {
+    return Status::Invalid("Trying to copy ", src_paths.size(), " files into ",
+                           dest_paths.size(), " paths.");
+  }
+
+  return ::arrow::internal::OptionalParallelFor(
+      use_threads, static_cast<int>(src_paths.size()), [&](int i) {
+        ARROW_ASSIGN_OR_RAISE(auto src, src_fs->OpenInputStream(src_paths[i]));
+        auto dest_dir = internal::GetAbstractPathParent(dest_paths[i]).first;
+        if (!dest_dir.empty()) {
+          RETURN_NOT_OK(dest_fs->CreateDir(dest_dir));
+        }
+        ARROW_ASSIGN_OR_RAISE(auto dest, dest_fs->OpenOutputStream(dest_paths[i]));
+        return internal::CopyStream(src, dest, chunk_size);

Review comment:
       Writing is typically asynchronous. A separate write thread may speed up things a little, but I don't think it would make a sizable difference.




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