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From viirya <...@git.apache.org>
Subject [GitHub] spark pull request: [SPARK-6145] [SQL] Fix the bug of nested data ...
Date Thu, 05 Mar 2015 11:49:25 GMT
Github user viirya commented on a diff in the pull request:

    https://github.com/apache/spark/pull/4892#discussion_r25857907
  
    --- Diff: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/LogicalPlan.scala
---
    @@ -192,14 +193,17 @@ abstract class LogicalPlan extends QueryPlan[LogicalPlan] with Logging
{
     
           // One match, but we also need to extract the requested nested field.
           case Seq((a, nestedFields)) =>
    -        // The foldLeft adds UnresolvedGetField for every remaining parts of the name,
    -        // and aliased it with the last part of the name.
    -        // For example, consider name "a.b.c", where "a" is resolved to an existing attribute.
    -        // Then this will add UnresolvedGetField("b") and UnresolvedGetField("c"), and
alias
    -        // the final expression as "c".
    -        val fieldExprs = nestedFields.foldLeft(a: Expression)(UnresolvedGetField)
    -        val aliasName = nestedFields.last
    -        Some(Alias(fieldExprs, aliasName)())
    +        // The foldLeft will resolve all of the nested data type, to get its attributes.
    +        val fieldExprs = nestedFields.foldLeft(a: Expression) { case (e, fieldName) =>
    +          resolveGetField(e, fieldName, resolver)
    +        }
    +
    +        // TODO the alias name is quite tricky to me, set it to _col1, _col2.. ?
    +        // Set it as original attribute name like "a.b.c" seems still confusing,
    +        // and we may never reference this column by its name (with "."), except
    +        // people write SQL like: SELECT a.b.c as newCol FROM nestedTable, which
    +        // explicitly specifying the alias name for the output column
    +        Some(Alias(fieldExprs, name)())
    --- End diff --
    
    I meant should it be that? In Hive it should be `c` instead of `a.b.c`?


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