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  1. Hive
  2. HIVE-2120

auto convert map join may miss good candidates

    Details

    • Type: Bug
    • Status: Closed
    • Priority: Major
    • Resolution: Fixed
    • Affects Version/s: None
    • Fix Version/s: 0.8.0
    • Component/s: Query Processor
    • Labels:
      None
    • Hadoop Flags:
      Reviewed

      Description

      In case in a join, there is a subquery which does a simple select, the auto convert map join may miss a good candidate at run time. The plan generated is correct, but the selection at runtime has a bug.

      For example:
      set hive.smalltable.filesize=1000;
      create table src_one as select * from src where key=100;
      select count(1)
      from
      (
      select * from src
      ) subq
      join
      src_small on src.key = subq.key;

      The table src_small can be a small table. This is in the plan, but at runtime it gets filtered out.

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            • Assignee:
              he yongqiang He Yongqiang
              Reporter:
              he yongqiang He Yongqiang
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              • Created:
                Updated:
                Resolved: