matthewgapp commented on code in PR #8839:
URL: https://github.com/apache/arrow-datafusion/pull/8839#discussion_r1457901521
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datafusion/expr/src/logical_plan/plan.rs:
##########
@@ -1718,6 +1751,42 @@ pub struct EmptyRelation {
pub schema: DFSchemaRef,
}
+/// A variadic query operation, Recursive CTE.
+///
+/// # Recursive Query Evaluation
+///
+/// From the [Postgres Docs]:
+///
+/// 1. Evaluate the non-recursive term. For `UNION` (but not `UNION ALL`),
+/// discard duplicate rows. Include all remaining rows in the result of the
+/// recursive query, and also place them in a temporary working table.
+//
+/// 2. So long as the working table is not empty, repeat these steps:
+///
+/// * Evaluate the recursive term, substituting the current contents of the
+/// working table for the recursive self-reference. For `UNION` (but not `UNION
+/// ALL`), discard duplicate rows and rows that duplicate any previous result
+/// row. Include all remaining rows in the result of the recursive query, and
+/// also place them in a temporary intermediate table.
+///
+/// * Replace the contents of the working table with the contents of the
+/// intermediate table, then empty the intermediate table.
+///
+/// [Postgres Docs]:
https://www.postgresql.org/docs/current/queries-with.html#QUERIES-WITH-RECURSIVE
+#[derive(Clone, PartialEq, Eq, Hash)]
+pub struct RecursiveQuery {
+ /// Name of the query
+ pub name: String,
+ /// The static term (initial contents of the working table)
+ pub static_term: Arc<LogicalPlan>,
+ /// The recursive term (evaluated on the contents of the working table
until
+ /// it returns an empty set)
+ pub recursive_term: Arc<LogicalPlan>,
+ /// Should the output of the recursive term be deduplicated (`UNION`) or
+ /// not (`UNION ALL`).
+ pub is_distinct: bool,
Review Comment:
what about `dedupe`? Regardless, I would prefer if we made this naming
change in a follow-on PR once we merge this and the execution PR.
##########
datafusion/expr/src/logical_plan/builder.rs:
##########
@@ -121,6 +123,27 @@ impl LogicalPlanBuilder {
}))
}
+ /// Convert a regular plan into a recursive query.
Review Comment:
yup!
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