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Review request for hive and Ning Zhang. Summary ------- By tweaking the RCFile$Reader implementation to allow more efficient memory access I was able to reduce CPU usage. I measured the speed required to scan a gzipped RCFile, decompress and assemble into records. CPU time was reduced by about 7% for a full table scan, An improvement of about 2% was realised when a smaller subset of columns (3-5 out of tens) were selected. This addresses bug HIVE-2350. https://issues.apache.org/jira/browse/HIVE-2350 Diffs ----- trunk/ql/src/java/org/apache/hadoop/hive/ql/io/RCFile.java 1154070 Diff: https://reviews.apache.org/r/1309/diff Testing ------- Ran TestRCFile unit test. Manually tested reading from warehouse table. Thanks, Tim