gruuya commented on code in PR #7981:
URL: https://github.com/apache/arrow-datafusion/pull/7981#discussion_r1377481562
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datafusion/expr/src/logical_plan/plan.rs:
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@@ -2132,9 +2181,96 @@ pub struct Limit {
/// Removes duplicate rows from the input
#[derive(Clone, PartialEq, Eq, Hash)]
-pub struct Distinct {
+pub enum Distinct {
+ /// Plain `DISTINCT` referencing all selection expressions
+ All(Arc<LogicalPlan>),
+ /// The `Postgres` addition, allowing separate control over DISTINCT'd and
selected columns
+ On(DistinctOn),
+}
+
+/// Removes duplicate rows from the input
+#[derive(Clone, PartialEq, Eq, Hash)]
+pub struct DistinctOn {
+ /// The `DISTINCT ON` clause expression list
+ pub on_expr: Vec<Expr>,
+ /// The selected projection expression list
+ pub select_expr: Vec<Expr>,
+ /// The `ORDER BY` clause, whose initial expressions must match those of
the `ON` clause
+ pub sort_expr: Option<Vec<Expr>>,
/// The logical plan that is being DISTINCT'd
pub input: Arc<LogicalPlan>,
+ /// The schema description of the DISTINCT ON output
+ pub schema: DFSchemaRef,
+}
+
+impl DistinctOn {
+ /// Create a new `DistintOn` struct.
+ pub fn try_new(
+ on_expr: Vec<Expr>,
+ select_expr: Vec<Expr>,
+ sort_expr: Option<Vec<Expr>>,
+ input: Arc<LogicalPlan>,
+ ) -> Result<Self> {
+ let on_expr = normalize_cols(on_expr, input.as_ref())?;
+
+ // Create fields with any qualifier stuffed in the name itself
Review Comment:
This is sort of a hack, but the reason I was forced to do it is so that the
plan schema remains unchanged after `replace_distinct_aggregate`. In
particular, in that optimizer I alias the final projected expressions with the
selection expression display name, but that always results in a schema without
qualifiers (with any original qualifier crammed into the field name).
I feel like this case should be handled by `Projection::try_new_with_schema`
over at `replace_distinct_aggregate`, but it seems that after #7919 the custom
schema doesn't propagate through the optimization chain.
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