Zoltan Borok-Nagy has posted comments on this change. ( http://gerrit.cloudera.org:8080/12238 )
Change subject: IMPALA-8090: race when reusing ScanRange in test ...................................................................... Patch Set 2: (2 comments) When I have some time I'll come back to scan ranges in the context of IMPALA-7556, because I always find some peculiar and shady stuff going on here :) http://gerrit.cloudera.org:8080/#/c/12238/2/be/src/runtime/io/scan-range.cc File be/src/runtime/io/scan-range.cc: http://gerrit.cloudera.org:8080/#/c/12238/2/be/src/runtime/io/scan-range.cc@211 PS2, Line 211: Open side note: In HdfsFileReader::Open() there is an unnecessary hdfsSeek() that always seeks to the beginning of the ScanRange. Then we also perform an hdfsSeek()/hdfsPread() in ReadFromPos(). I'm not sure about the overhead of it, but if some parts of the system do some speculative pre-fetching based on hdfsSeek(), it can hurt. Though it only happens when file handle caching is used. http://gerrit.cloudera.org:8080/#/c/12238/2/be/src/runtime/io/scan-range.cc@240 PS2, Line 240: file_reader_->Close(); This bug existed earlier as well, but FileReader::Close() is not idempotent, and it is also called in CancelInternal(). -- To view, visit http://gerrit.cloudera.org:8080/12238 To unsubscribe, visit http://gerrit.cloudera.org:8080/settings Gerrit-Project: Impala-ASF Gerrit-Branch: master Gerrit-MessageType: comment Gerrit-Change-Id: I3122e5b2efea60ffe82d780930301d5be108876b Gerrit-Change-Number: 12238 Gerrit-PatchSet: 2 Gerrit-Owner: Tim Armstrong <[email protected]> Gerrit-Reviewer: Zoltan Borok-Nagy <[email protected]> Gerrit-Comment-Date: Mon, 21 Jan 2019 14:32:39 +0000 Gerrit-HasComments: Yes
