[GitHub] mn-mikke commented on issue #23745: [SPARK-26707][SQL] Insertion of a single struct into a table

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mn-mikke commented on issue #23745: [SPARK-26707][SQL] Insertion of a single struct into a table
URL: https://github.com/apache/spark/pull/23745#issuecomment-461621842
 
 
   Hi @hvanhovell,
   the problem is caused by the grammar rule for [```primaryExpression```](https://github.com/apache/spark/blob/b4e1d145135445eeed85784dab0c2c088930dd26/sql/catalyst/src/main/antlr4/org/apache/spark/sql/catalyst/parser/SqlBase.g4#L590) and two roles of the ```CreateNamedStruct``` expression.
   
   If the inline table has more columns, the [```rowConstructor```](https://github.com/apache/spark/blob/b4e1d145135445eeed85784dab0c2c088930dd26/sql/catalyst/src/main/antlr4/org/apache/spark/sql/catalyst/parser/SqlBase.g4#L601) branch is called and plays role of  a container for holding all value expressions and propagating them from a call of [```visitRowConstructor```](https://github.com/apache/spark/blob/b4e1d145135445eeed85784dab0c2c088930dd26/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/parser/AstBuilder.scala#L1410) to a call of [```visitInlineTable```](https://github.com/apache/spark/blob/b4e1d145135445eeed85784dab0c2c088930dd26/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/parser/AstBuilder.scala#L842) where the ```CreateNamedStruct``` expression is removed.
   
   If the inline table has only one column of structs, the  [```struct```](https://github.com/apache/spark/blob/b4e1d145135445eeed85784dab0c2c088930dd26/sql/catalyst/src/main/antlr4/org/apache/spark/sql/catalyst/parser/SqlBase.g4#L594) branch (optionally via [```parenthizedExpression```](https://github.com/apache/spark/blob/b4e1d145135445eeed85784dab0c2c088930dd26/sql/catalyst/src/main/antlr4/org/apache/spark/sql/catalyst/parser/SqlBase.g4#L612)) is called and [```visitInlineTable```](https://github.com/apache/spark/blob/b4e1d145135445eeed85784dab0c2c088930dd26/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/parser/AstBuilder.scala#L842) removes the struct as well and that is **the problem**.
   
   Yeah, maybe a change in the grammar as such will be more convenient... WDYT?

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