EnricoMi commented on code in PR #37407:
URL: https://github.com/apache/spark/pull/37407#discussion_r981083737
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sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/parser/AstBuilder.scala:
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@@ -1098,6 +1106,87 @@ class AstBuilder extends
SqlBaseParserBaseVisitor[AnyRef] with SQLConfHelper wit
}
}
+ /**
+ * Add an [[Unpivot]] to a logical plan.
+ */
+ private def withUnpivot(
+ ctx: UnpivotClauseContext,
+ query: LogicalPlan): LogicalPlan = withOrigin(ctx) {
+ // this is needed to create unpivot and to filter unpivot for nulls
further down
+ val valueColumnNames =
+ Option(ctx.unpivotOperator().unpivotSingleValueColumnClause())
+ .map(_.unpivotValueColumn().identifier().getText)
+ .map(Seq(_))
+ .getOrElse(
+ Option(ctx.unpivotOperator().unpivotMultiValueColumnClause())
+ .map(_.unpivotValueColumns.asScala.map(_.identifier().getText).toSeq)
+ .get
+ )
+
+ val unpivot = if (ctx.unpivotOperator().unpivotSingleValueColumnClause()
!= null) {
+ val unpivotClause =
ctx.unpivotOperator().unpivotSingleValueColumnClause()
+ val variableColumnName =
unpivotClause.unpivotNameColumn().identifier().getText
+ val unpivotColumns =
unpivotClause.unpivotColumns.asScala.map(visitUnpivotColumn).toSeq
+
+ Unpivot(
+ None,
+ Some(unpivotColumns.map(Seq(_))),
+ None,
+ variableColumnName,
+ valueColumnNames,
+ query
+ )
+ } else {
+ val unpivotClause = ctx.unpivotOperator().unpivotMultiValueColumnClause()
+ val variableColumnName =
unpivotClause.unpivotNameColumn().identifier().getText
+ val (unpivotColumns, unpivotAliases) =
+
unpivotClause.unpivotColumnSets.asScala.map(visitUnpivotColumnSet).toSeq.unzip
+
+ Unpivot(
+ None,
+ Some(unpivotColumns),
+ Some(unpivotAliases),
+ variableColumnName,
+ valueColumnNames,
+ query
+ )
+ }
+
+ // exclude null values
+ val filtered = if (ctx.nullOperator != null && ctx.nullOperator.EXCLUDE()
!= null) {
+
Filter(IsNotNull(Coalesce(valueColumnNames.map(UnresolvedAttribute(_)))),
unpivot)
Review Comment:
[Oracle](https://www.oracletutorial.com/oracle-basics/oracle-unpivot/) is
not specific about this, nor provides it an example that exemplifies NULL
values with multiple unpivot columns:
The EXCLUDE NULLS clause, on the other hand, eliminates null-valued rows
from the returned result set.
[BigQuery](https://cloud.google.com/bigquery/docs/reference/standard-sql/query-syntax#unpivot_operator)
EXCLUDE NULLS: Do not add rows with NULL values to the result.
From
[here](https://stackoverflow.com/questions/10747355/oracle-11g-unpivot-multiple-columns-and-include-column-name)
it looks like Oracle behaves the same.
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