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CreateStruct Function Builder

CreateStruct is a <> (e.g. Seq[Expression] => Expression) that can <> and is the <> of the <> function.

=== [[registryEntry]] Metadata of struct Function -- registryEntry Property

[source, scala]

registryEntry: (String, (ExpressionInfo, FunctionBuilder))

registryEntry...FIXME

NOTE: registryEntry is used exclusively when FunctionRegistry is requested for the <>.

=== [[apply]] Creating CreateNamedStruct Expression -- apply Method

[source, scala]

apply(children: Seq[Expression]): CreateNamedStruct

NOTE: apply is part of Scala's https://www.scala-lang.org/api/2.11.12/index.html#scala.Function1[scala.Function1] contract to create a function of one parameter (e.g. Seq[Expression]).

apply creates a <> expression with the input children <> as follows:

  • For <> expressions that are <>, apply creates a pair of a <> expression (with the <> of the NamedExpression) and the NamedExpression itself

  • For <> expressions that are not <> yet, apply creates a pair of a NamePlaceholder expression and the NamedExpression itself

  • For all other <>, apply creates a pair of a <> expression (with the value as col[index]) and the Expression itself

apply is used when:

  • ResolveReferences logical resolution rule is requested to expandStarExpression

  • InConversion type coercion rule is requested to coerceTypes

  • ExpressionEncoder is requested to create an ExpressionEncoder for a tuple

  • Stack generator expression is requested to <>

  • AstBuilder is requested to parse a <> and <>

  • ColumnStat is requested to <>

  • KeyValueGroupedDataset is requested to aggUntyped (when KeyValueGroupedDataset.agg typed operator is used)

  • <> typed transformation is used

  • <> standard function is used

  • SimpleTypedAggregateExpression expression is requested evaluateExpression and resultObjToRow

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