[jira] [Created] (SPARK-32848) Let CostBasedJoinReorder produce deterministic result with Scala 2.12 and 2.13

["Yang Jie (Jira)" <ji...@apache.org>]

Yang Jie created SPARK-32848:
--------------------------------

             Summary: Let CostBasedJoinReorder produce deterministic result with Scala 2.12 and 2.13
                 Key: SPARK-32848
                 URL: https://issues.apache.org/jira/browse/SPARK-32848
             Project: Spark
          Issue Type: Improvement
          Components: SQL
    Affects Versions: 3.0.1, 3.0.0, 3.1.0
            Reporter: Yang Jie


The optimization result of {{CostBasedJoinReorder}} maybe different with same input in Scala 2.12 and Scala 2.13 if there are more than one same cost candidate plans.

The test case named "Test 4: Star with several branches" in StarJoinCostBasedReorderSuite is a typical case.

 

If the input is 
{code:java}
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")))

{code}
the optimization result  in Scala 2.12 is 
{code:java}
  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")))
    .
    .
    .{code}
and the optimization result  in Scala 2.13 is 
{code:java}
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")))
    .
    .
    .
{code}
 



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