mingmwang commented on code in PR #5322:
URL: https://github.com/apache/arrow-datafusion/pull/5322#discussion_r1116468631
##########
datafusion/physical-expr/src/utils.rs:
##########
@@ -235,6 +234,82 @@ pub fn ordering_satisfy_concrete<F: FnOnce() ->
EquivalenceProperties>(
}
}
+#[derive(Clone, Debug)]
+pub struct ExprTreeNode<T> {
+ expr: Arc<dyn PhysicalExpr>,
+ data: Option<T>,
+ child_nodes: Vec<ExprTreeNode<T>>,
+}
+
+impl<T> ExprTreeNode<T> {
+ pub fn new(expr: Arc<dyn PhysicalExpr>) -> Self {
+ ExprTreeNode {
+ expr,
+ data: None,
+ child_nodes: vec![],
+ }
+ }
+
+ pub fn expression(&self) -> &Arc<dyn PhysicalExpr> {
+ &self.expr
+ }
+
+ pub fn children(&self) -> Vec<ExprTreeNode<T>> {
+ self.expr
+ .children()
+ .into_iter()
+ .map(ExprTreeNode::new)
+ .collect()
+ }
+}
+
+impl<T: Clone> TreeNodeRewritable for ExprTreeNode<T> {
+ fn map_children<F>(mut self, transform: F) -> Result<Self>
+ where
+ F: FnMut(Self) -> Result<Self>,
+ {
+ self.child_nodes = self
+ .children()
+ .into_iter()
+ .map(transform)
+ .collect::<Result<Vec<_>>>()?;
+ Ok(self)
+ }
+}
+
+/// This function converts the [PhysicalExpr] tree into a DAG by collecting
identical
+/// expressions in one node. Caller specifies the node type in this DAG via the
+/// `constructor` argument, which constructs nodes in this DAG from the
[ExprTreeNode]
+/// ancillary object.
+pub fn build_dag<T, F>(
+ expr: Arc<dyn PhysicalExpr>,
+ constructor: &F,
+) -> Result<(NodeIndex, StableGraph<T, usize>)>
Review Comment:
Is there any UT for the `build_dag` ?
I try to understand the implementation but there are so many structs
involved here and I get lost soon.
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