Dan Hecht has posted comments on this change. Change subject: IMPALA-5036: Parquet count star optimization ......................................................................
Patch Set 5: (3 comments) http://gerrit.cloudera.org:8080/#/c/6812/5/fe/src/main/java/org/apache/impala/catalog/BuiltinsDb.java File fe/src/main/java/org/apache/impala/catalog/BuiltinsDb.java: Line 886: prefix + "8InitZeroIN10impala_udf9BigIntValEEEvPNS2_15FunctionContextEPT_", > I gave this a try, but ran into a problem. I tried substituting a count(*) You'd have to replace the uses of the agg slot with the zeroifnull() expression. If that's too complicated, then I'm fine with leaving it. I still think, conceptually, it's cleaner to be able to do rewrites using existing expressions rather than build new ones, but if it doesn't work out given our current optimizer, then so be it. http://gerrit.cloudera.org:8080/#/c/6812/5/fe/src/main/java/org/apache/impala/planner/HdfsScanNode.java File fe/src/main/java/org/apache/impala/planner/HdfsScanNode.java: Line 109: * > This is the only one (I think it's pretty high level). This comment doesn't explain the overall optimization. What I'm looking for is something that explains the optimization: what the rewrite is, and what the "special" scan is. PS5, Line 140: This : // scan does additional analysis in init() to determine whether it is correct to apply : // the optimization. > An alternative approach that Alex and I are thinking about is passing in th Okay. If it doesn't work out, I just think the comments needs to be clarified. Future readers won't be looking at this code review to understand the code. -- To view, visit http://gerrit.cloudera.org:8080/6812 To unsubscribe, visit http://gerrit.cloudera.org:8080/settings Gerrit-MessageType: comment Gerrit-Change-Id: I536b85c014821296aed68a0c68faadae96005e62 Gerrit-PatchSet: 5 Gerrit-Project: Impala-ASF Gerrit-Branch: master Gerrit-Owner: Taras Bobrovytsky <tbobrovyt...@cloudera.com> Gerrit-Reviewer: Alex Behm <alex.b...@cloudera.com> Gerrit-Reviewer: Dan Hecht <dhe...@cloudera.com> Gerrit-Reviewer: Lars Volker <l...@cloudera.com> Gerrit-Reviewer: Marcel Kornacker <mar...@cloudera.com> Gerrit-Reviewer: Mostafa Mokhtar <mmokh...@cloudera.com> Gerrit-Reviewer: Taras Bobrovytsky <tbobrovyt...@cloudera.com> Gerrit-Reviewer: Zach Amsden <zams...@cloudera.com> Gerrit-HasComments: Yes
