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Posted to issues@spark.apache.org by "Yerui Sun (JIRA)" <ji...@apache.org> on 2016/11/29 09:14:59 UTC

[jira] [Created] (SPARK-18622) Missing Reference in Multi Union Clauses Cause by TypeCoercion

Yerui Sun created SPARK-18622:
---------------------------------

             Summary: Missing Reference in Multi Union Clauses Cause by TypeCoercion
                 Key: SPARK-18622
                 URL: https://issues.apache.org/jira/browse/SPARK-18622
             Project: Spark
          Issue Type: Bug
          Components: SQL
    Affects Versions: 2.0.2, 1.6.3
            Reporter: Yerui Sun


{code}
spark-sql> explain extended
         > select a
         > from
         > (
         >   select 0 a, 0 b
         > union all
         >   select sum(1) a, cast(0 as bigint) b
         > union all
         >   select 0 a, 0 b
         > )t;
 
== Parsed Logical Plan ==
'Project ['a]
+- 'SubqueryAlias t
   +- 'Union
      :- 'Union
      :  :- Project [0 AS a#0, 0 AS b#1]
      :  :  +- OneRowRelation$
      :  +- 'Project ['sum(1) AS a#2, cast(0 as bigint) AS b#3L]
      :     +- OneRowRelation$
      +- Project [0 AS a#4, 0 AS b#5]
         +- OneRowRelation$
 
== Analyzed Logical Plan ==
a: int
Project [a#0]
+- SubqueryAlias t
   +- Union
      :- !Project [a#0, b#9L]
      :  +- Union
      :     :- Project [cast(a#0 as bigint) AS a#11L, b#9L]
      :     :  +- Project [a#0, cast(b#1 as bigint) AS b#9L]
      :     :     +- Project [0 AS a#0, 0 AS b#1]
      :     :        +- OneRowRelation$
      :     +- Project [a#2L, b#3L]
      :        +- Project [a#2L, b#3L]
      :           +- Aggregate [sum(cast(1 as bigint)) AS a#2L, cast(0 as bigint) AS b#3L]
      :              +- OneRowRelation$
      +- Project [a#4, cast(b#5 as bigint) AS b#10L]
         +- Project [0 AS a#4, 0 AS b#5]
            +- OneRowRelation$
 
== Optimized Logical Plan ==
org.apache.spark.sql.AnalysisException: resolved attribute(s) a#0 missing from a#11L,b#9L in operator !Project [a#0, b#9L];;
Project [a#0]
+- SubqueryAlias t
   +- Union
      :- !Project [a#0, b#9L]
      :  +- Union
      :     :- Project [cast(a#0 as bigint) AS a#11L, b#9L]
      :     :  +- Project [a#0, cast(b#1 as bigint) AS b#9L]
      :     :     +- Project [0 AS a#0, 0 AS b#1]
      :     :        +- OneRowRelation$
      :     +- Project [a#2L, b#3L]
      :        +- Project [a#2L, b#3L]
      :           +- Aggregate [sum(cast(1 as bigint)) AS a#2L, cast(0 as bigint) AS b#3L]
      :              +- OneRowRelation$
      +- Project [a#4, cast(b#5 as bigint) AS b#10L]
         +- Project [0 AS a#4, 0 AS b#5]
            +- OneRowRelation$
 
== Physical Plan ==
org.apache.spark.sql.AnalysisException: resolved attribute(s) a#0 missing from a#11L,b#9L in operator !Project [a#0, b#9L];;
Project [a#0]
+- SubqueryAlias t
   +- Union
      :- !Project [a#0, b#9L]
      :  +- Union
      :     :- Project [cast(a#0 as bigint) AS a#11L, b#9L]
      :     :  +- Project [a#0, cast(b#1 as bigint) AS b#9L]
      :     :     +- Project [0 AS a#0, 0 AS b#1]
      :     :        +- OneRowRelation$
      :     +- Project [a#2L, b#3L]
      :        +- Project [a#2L, b#3L]
      :           +- Aggregate [sum(cast(1 as bigint)) AS a#2L, cast(0 as bigint) AS b#3L]
      :              +- OneRowRelation$
      +- Project [a#4, cast(b#5 as bigint) AS b#10L]
         +- Project [0 AS a#4, 0 AS b#5]
            +- OneRowRelation$
{code}

Key Points to re-produce issue:
* 3 or more union clauses;
* One column is sum aggregate in one union clause, and is Integer type in other union clause;
* Another column has different date types in union clauses;

The reason of issue:
- Step 1: Apply TypeCoercion.WidenSetOperationTypes, add project with cast since the union clauses has different datatypes for one column; With 3 union clauses, the inner union clause also be projected with cast;
- Step 2: Apply TypeCoercion.FunctionArgumentConversion, the return type of sum(int) will be extended to BigInt, meaning one column in union clauses changed datatype;
- Step 3: Apply TypeCoercion.WidenSetOperationTypes again, another cast project added in inner union clause, since sum(int) datatype changed; at this point, the reference of project ON inner union will be missed, since the project IN inner union is newly added, see the  Analyzed Logical Plan;

Solutions to fix:
* Since set operation type coercion should be applied after inner clause be stabled, apply WidenSetOperationTypes at last will fix the issue;
* To avoiding multi level projects on set operation clause, handle the existing cast project carefully in WidenSetOperationTypes should be also work;

Appreciate for any comments.



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