jayzhan211 commented on code in PR #26269:
URL: https://github.com/apache/datafusion/pull/26269#discussion_r4366534277
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datafusion/expr/src/logical_plan/materialized_cte.rs:
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@@ -62,91 +65,198 @@ impl fmt::Display for MaterializedCteId {
}
}
+/// A node of a materialized CTE, in [`LogicalPlan::MaterializedCte`].
+#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Hash)]
+pub enum MaterializedCtePlan {
+ /// Computes the body of the CTE once and evaluates the continuation
+ Cte(MaterializedCte),
+ /// Reads the buffered output of the CTE. This is a leaf.
+ Scan(MaterializedCteScan),
+}
+
/// Computes `cte` once and evaluates `continuation`, in which every
/// [`MaterializedCteScan`] with the same `id` reads the buffered output of
/// `cte`. The output of this node is the output of `continuation`.
+///
+/// The node has two inputs with different roles, in this order:
+///
+/// 1. `cte`: the body of the CTE. It is shared by all the scans, so a rule
+/// must not change its schema, and must not push into it a filter, limit
+/// or projection that belongs to one scan only.
+/// 2. `continuation`: the query that declared the CTE.
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct MaterializedCte {
+ /// Binds the scans in `continuation` to this node
pub id: MaterializedCteId,
+ /// Name of the CTE, used for display and error messages only
pub name: String,
- pub cte: LogicalPlan,
- pub continuation: LogicalPlan,
+ /// The body of the CTE
+ pub cte: Arc<LogicalPlan>,
Review Comment:
nit: the field is `cte` but the accessor is `body()`, so call sites end up
reading `cte.cte` (e.g. in `decorrelate.rs` and `optimize_projections`). Since
#25580 hasn't shipped in a release yet, renaming the field to `body` now would
be free:
```diff
- pub cte: Arc<LogicalPlan>,
+ pub body: Arc<LogicalPlan>,
```
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