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Posted to reviews@spark.apache.org by GitBox <gi...@apache.org> on 2020/09/10 16:37:05 UTC

[GitHub] [spark] LuciferYang commented on pull request #29718: [SPARK-32848][SQL] Let CostBasedJoinReorder produce same result with same input in Scala 2.12 and 2.13

LuciferYang commented on pull request #29718:
URL: https://github.com/apache/spark/pull/29718#issuecomment-690471480


   The test case named "Test 4: Star with several branches" in StarJoinCostBasedReorderSuite is a typical case.
   
   If the input is 
   ```
   d1.join(t3).join(t4).join(f1).join(d2).join(t5).join(t6).join(d3).join(t1).join(t2)
     .where((nameToAttr("d1_c2") === nameToAttr("t3_c1")) &&
       (nameToAttr("t3_c2") === nameToAttr("t4_c2")) &&
       (nameToAttr("d1_pk") === nameToAttr("f1_fk1")) &&
       (nameToAttr("f1_fk2") === nameToAttr("d2_pk")) &&
       (nameToAttr("d2_c2") === nameToAttr("t5_c1")) &&
       (nameToAttr("t5_c2") === nameToAttr("t6_c2")) &&
       (nameToAttr("f1_fk3") === nameToAttr("d3_pk")) &&
       (nameToAttr("d3_c2") === nameToAttr("t1_c1")) &&
       (nameToAttr("t1_c2") === nameToAttr("t2_c2")))
   ```
   
   the optimization result  in Scala 2.12 is 
   
   ```
     f1.join(d3, Inner, Some(nameToAttr("f1_fk3") === nameToAttr("d3_pk")))
       .join(d1, Inner, Some(nameToAttr("f1_fk1") === nameToAttr("d1_pk")))
       .join(d2, Inner, Some(nameToAttr("f1_fk2") === nameToAttr("d2_pk")))
       .
       .
       .
   ```
   
   and the optimization result  in Scala 2.13 is 
   
   ```
   f1.join(d3, Inner, Some(nameToAttr("f1_fk3") === nameToAttr("d3_pk")))
       .join(d2, Inner, Some(nameToAttr("f1_fk2") === nameToAttr("d2_pk")))
       .join(d1, Inner, Some(nameToAttr("f1_fk1") === nameToAttr("d1_pk")))
       .
       .
       .
   ```


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