viirya commented on code in PR #8626:
URL: https://github.com/apache/arrow-datafusion/pull/8626#discussion_r1435683995
##########
datafusion/optimizer/src/push_down_filter.rs:
##########
@@ -955,6 +965,36 @@ impl PushDownFilter {
}
}
+/// Convert cross join to join by pushing down filter predicate to the join
condition
+fn convert_cross_join_to_inner_join(cross_join: CrossJoin) -> Result<Join> {
+ let CrossJoin { left, right, .. } = cross_join;
+ let join_schema = build_join_schema(left.schema(), right.schema(),
&JoinType::Inner)?;
+ // predicate is given
+ Ok(Join {
+ left,
+ right,
+ join_type: JoinType::Inner,
+ join_constraint: JoinConstraint::On,
+ on: vec![],
+ filter: None,
+ schema: DFSchemaRef::new(join_schema),
+ null_equals_null: true,
+ })
+}
+
+/// Converts the inner join with empty equality predicate and empty filter
condition to the cross join
+fn convert_to_cross_join_if_beneficial(plan: LogicalPlan) ->
Result<LogicalPlan> {
+ if let LogicalPlan::Join(join) = &plan {
+ // Can be converted back to cross join
+ if join.on.is_empty() && join.filter.is_none() {
+ return LogicalPlanBuilder::from(join.left.as_ref().clone())
+ .cross_join(join.right.as_ref().clone())?
+ .build();
+ }
+ }
+ Ok(plan)
+}
Review Comment:
Hmm, after `push_down_all_join`, if there are predicates that cannot be join
condition, they will be into a `Filter` on top of join node. In the case, this
function will skip to convert the under join to cross join?
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