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d19751669a
Currently we don't reset the file read offset if ZCR fails. Due to this, when we switch to the normal read path, we hit the eosr of the scan-range even before reading the expected data length. If both the ReadFromCache() and ReadRange() calls fail without reading any data, we end up creating a whole list of scan-ranges, each with size 1KB (DEFAULT_READ_PAST_SIZE) assuming we are reading past the scan range. This gives a huge performance hit. This patch just calls ScanRange::Close() after the failed cache reads to clean up the file system state so that the re-reads start from beginning of the scan range. This was hit as a part of debugging IMPALA-3679, where the queries on 1gb cached data were running ~20x slower compared to non-cached runs. Change-Id: I0a9ea19dd8571b01d2cd5b87da1c259219f6297a Reviewed-on: http://gerrit.cloudera.org:8080/3313 Reviewed-by: Michael Brown <mikeb@cloudera.com> Tested-by: Bharath Vissapragada <bharathv@cloudera.com>