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 for the <> and <>