pitrou commented on a change in pull request #7172:
URL: https://github.com/apache/arrow/pull/7172#discussion_r425166680
##########
File path: cpp/src/arrow/io/file.cc
##########
@@ -262,6 +266,27 @@ class ReadableFile::ReadableFileImpl : public OSFile {
return std::move(buffer);
}
+ Status WillNeed(const std::vector<ReadRange>& ranges) {
+ RETURN_NOT_OK(CheckClosed());
+ for (const auto& range : ranges) {
+ RETURN_NOT_OK(internal::ValidateRange(range.offset, range.length));
+#if defined(POSIX_FADV_WILLNEED)
+ if (posix_fadvise(fd_, range.offset, range.length, POSIX_FADV_WILLNEED))
{
+ return IOErrorFromErrno(errno, "posix_fadvise failed");
+ }
+#elif defined(F_RDADVISE) // macOS, BSD?
+ struct {
+ off_t ra_offset;
+ int ra_count;
+ } radvisory{range.offset, static_cast<int>(range.length)};
Review comment:
Not really important: it's just an advisory anyway. At worse the kernel
will readahead too little.
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