mingmwang commented on code in PR #6457:
URL: https://github.com/apache/arrow-datafusion/pull/6457#discussion_r1227887303
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datafusion/expr/src/logical_plan/plan.rs:
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@@ -402,6 +403,80 @@ impl LogicalPlan {
Ok(using_columns)
}
+ /// returns the first output expression of this `LogicalPlan` node.
+ pub fn head_output_expr(&self) -> Result<Option<Expr>> {
+ match self {
+ LogicalPlan::Projection(projection) => {
+ Ok(Some(projection.expr.as_slice()[0].clone()))
+ }
+ LogicalPlan::Aggregate(agg) => {
+ if agg.group_expr.is_empty() {
+ Ok(Some(agg.aggr_expr.as_slice()[0].clone()))
+ } else {
+ Ok(Some(agg.group_expr.as_slice()[0].clone()))
+ }
+ }
+ LogicalPlan::Filter(Filter { input, .. })
+ | LogicalPlan::Distinct(Distinct { input, .. })
+ | LogicalPlan::Sort(Sort { input, .. })
+ | LogicalPlan::Limit(Limit { input, .. })
+ | LogicalPlan::Repartition(Repartition { input, .. })
+ | LogicalPlan::Window(Window { input, .. }) =>
input.head_output_expr(),
+ LogicalPlan::Join(Join {
+ left,
+ right,
+ join_type,
+ ..
+ }) => match join_type {
+ JoinType::Inner | JoinType::Left | JoinType::Right |
JoinType::Full => {
+ if left.schema().fields().is_empty() {
+ right.head_output_expr()
+ } else {
+ left.head_output_expr()
+ }
+ }
+ JoinType::LeftSemi | JoinType::LeftAnti =>
left.head_output_expr(),
+ JoinType::RightSemi | JoinType::RightAnti =>
right.head_output_expr(),
+ },
+ LogicalPlan::CrossJoin(cross) => {
+ if cross.left.schema().fields().is_empty() {
+ cross.right.head_output_expr()
+ } else {
+ cross.left.head_output_expr()
+ }
+ }
+ LogicalPlan::Union(union) => Ok(Some(Expr::Column(
+ union.schema.fields()[0].qualified_column(),
+ ))),
+ LogicalPlan::TableScan(table) => Ok(Some(Expr::Column(
+ table.projected_schema.fields()[0].qualified_column(),
+ ))),
+ LogicalPlan::SubqueryAlias(subquery_alias) => {
+ let expr_opt = subquery_alias.input.head_output_expr()?;
+ expr_opt
+ .map(|expr| {
+ Ok(Expr::Column(create_col_from_scalar_expr(
+ &expr,
+ subquery_alias.alias.to_string(),
+ )?))
+ })
+ .map_or(Ok(None), |v| v.map(Some))
+ }
+ LogicalPlan::Subquery(_) => Ok(None),
+ LogicalPlan::EmptyRelation(_)
+ | LogicalPlan::Prepare(_)
+ | LogicalPlan::Statement(_)
+ | LogicalPlan::Values(_)
Review Comment:
I think currently we do not support `Values` clause inside the subquery.
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