Hello, We were comparing performance of some of our production hive queries between Hive and Spark. We compared Hive(0.13)+hadoop (1.2.1) against both Spark 0.9 and 1.1. We could see that the performance gains have been good in Spark.
We tried a very simple query, select count(*) from T where col3=123 in both sparkSQL and Hive (with hive.map.aggr=true) and found that Spark performance had been 2x better than Hive (120sec vs 60sec). Table T is stored in S3 and contains 600MB single GZIP file. My question is, why Spark is faster than Hive here? In both of the cases, the file will be downloaded, uncompressed and lines will be counted by a single process. For Hive case, reducer will be identity function since hive.map.aggr is true. Note that disk spills and network I/O are very less for Hive's case as well,
