mingmwang commented on code in PR #4185:
URL: https://github.com/apache/arrow-datafusion/pull/4185#discussion_r1020918310
##########
datafusion/optimizer/src/eliminate_cross_join.rs:
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@@ -44,143 +44,235 @@ impl ReduceCrossJoin {
}
}
+/// Attempt to reorder join tp reduce cross joins to inner joins.
+/// for queries:
+/// 'select ... from a, b where a.x = b.y and b.xx = 100;'
+/// 'select ... from a, b where (a.x = b.y and b.xx = 100) or (a.x = b.y and
b.xx = 200);'
+/// 'select ... from a, b, c where (a.x = b.y and b.xx = 100 and a.z = c.z)
+/// or (a.x = b.y and b.xx = 200 and a.z=c.z);'
+/// For above queries, the join predicate is available in filters and they are
moved to
+/// join nodes appropriately
+/// This fix helps to improve the performance of TPCH Q19. issue#78
+///
impl OptimizerRule for ReduceCrossJoin {
fn optimize(
&self,
plan: &LogicalPlan,
_optimizer_config: &mut OptimizerConfig,
) -> Result<LogicalPlan> {
- let mut possible_join_keys: Vec<(Column, Column)> = vec![];
- let mut all_join_keys = HashSet::new();
+ match plan {
+ LogicalPlan::Filter(filter) => {
+ let mut input = (**filter.input()).clone();
+
+ // optimize children.
+ input = self.optimize(&input, _optimizer_config)?;
+
Review Comment:
Should it call optimize children first ? I think this rule should be a
top-down(Preorder Traversal) optimization process.
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