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Posted to github@arrow.apache.org by "alamb (via GitHub)" <gi...@apache.org> on 2023/03/18 11:38:28 UTC
[GitHub] [arrow-datafusion] alamb commented on a diff in pull request #5630: Introduce a common trait TreeNode for ExecutionPlan, PhysicalExpr, LogicalExpr, LogicalPlan
alamb commented on code in PR #5630:
URL: https://github.com/apache/arrow-datafusion/pull/5630#discussion_r1140998574
##########
datafusion/common/src/tree_node.rs:
##########
Review Comment:
This API looks very nice 👌
##########
datafusion/core/src/datasource/listing/helpers.rs:
##########
@@ -36,48 +36,31 @@ use crate::{
use super::PartitionedFile;
use crate::datasource::listing::ListingTableUrl;
+use datafusion_common::tree_node::{Recursion, TreeNode};
use datafusion_common::{
cast::{as_date64_array, as_string_array, as_uint64_array},
Column, DataFusionError,
};
-use datafusion_expr::{
- expr_visitor::{ExprVisitable, ExpressionVisitor, Recursion},
- Expr, Volatility,
-};
+use datafusion_expr::{Expr, Volatility};
use object_store::path::Path;
use object_store::{ObjectMeta, ObjectStore};
const FILE_SIZE_COLUMN_NAME: &str = "_df_part_file_size_";
const FILE_PATH_COLUMN_NAME: &str = "_df_part_file_path_";
const FILE_MODIFIED_COLUMN_NAME: &str = "_df_part_file_modified_";
-/// The `ExpressionVisitor` for `expr_applicable_for_cols`. Walks the tree to
-/// validate that the given expression is applicable with only the `col_names`
-/// set of columns.
-struct ApplicabilityVisitor<'a> {
- col_names: &'a [String],
- is_applicable: &'a mut bool,
-}
-
-impl ApplicabilityVisitor<'_> {
- fn visit_volatility(self, volatility: Volatility) -> Recursion<Self> {
- match volatility {
- Volatility::Immutable => Recursion::Continue(self),
- // TODO: Stable functions could be `applicable`, but that would require access to the context
- Volatility::Stable | Volatility::Volatile => {
- *self.is_applicable = false;
- Recursion::Stop(self)
- }
- }
- }
-}
-
-impl ExpressionVisitor for ApplicabilityVisitor<'_> {
- fn pre_visit(self, expr: &Expr) -> Result<Recursion<Self>> {
- let rec = match expr {
+/// Check whether the given expression can be resolved using only the columns `col_names`.
+/// This means that if this function returns true:
+/// - the table provider can filter the table partition values with this expression
+/// - the expression can be marked as `TableProviderFilterPushDown::Exact` once this filtering
+/// was performed
+pub fn expr_applicable_for_cols(col_names: &[String], expr: &Expr) -> bool {
+ let mut is_applicable = true;
+ expr.collect(&mut |expr| {
Review Comment:
👍
##########
datafusion/physical-expr/src/tree_node/mod.rs:
##########
@@ -0,0 +1,266 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements. See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership. The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License. You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied. See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+//! This module provides common traits for visiting or rewriting tree nodes easily.
+//!
+//! It's a duplication of the one in the crate `datafusion-common`.
+//! In the future, if the Orphan rule is relaxed for Arc<dyn T>, these duplicated codes can be removed.
Review Comment:
It would be great if we could figure out how to avoid this duplication and the one in physical-expr?
Maybe we could create a blanket impl in `datafusion-common` like
```rust
impl<T: TreeNode> TreeNode for Arc<T> {
...
}
```
?
##########
datafusion/core/src/physical_optimizer/dist_enforcement.rs:
##########
@@ -925,7 +925,11 @@ impl PlanWithKeyRequirements {
}
}
-impl TreeNodeRewritable for PlanWithKeyRequirements {
+impl TreeNode for PlanWithKeyRequirements {
+ fn get_children(&self) -> Vec<Self> {
+ unimplemented!()
Review Comment:
Should this be implemented?
##########
datafusion/common/src/tree_node.rs:
##########
@@ -0,0 +1,261 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements. See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership. The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License. You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied. See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+//! This module provides common traits for visiting or rewriting tree nodes easily.
+
+use crate::{DataFusionError, Result};
+
+/// Trait for tree node. It can be [`ExecutionPlan`], [`PhysicalExpr`], [`LogicalExpr`], etc.
+pub trait TreeNode: Clone {
+ /// Return the children of this tree node
+ fn get_children(&self) -> Vec<Self>;
+
+ /// Use preorder to iterate the node on the tree so that we can stop fast for some cases.
+ ///
+ /// `op` can be used to collect some info from the tree node.
+ fn collect<F>(&self, op: &mut F) -> Result<()>
+ where
+ F: FnMut(&Self) -> Result<Recursion>,
+ {
+ match op(self)? {
+ Recursion::Continue => {}
+ // If the recursion should stop, do not visit children
+ Recursion::Stop => return Ok(()),
+ r => {
+ return Err(DataFusionError::Execution(format!(
+ "Recursion {r:?} is not supported for collect"
+ )))
+ }
+ };
+
+ for child in self.get_children() {
+ child.collect(op)?;
+ }
+
+ Ok(())
+ }
+
+ /// Visit the tree node using the given [TreeNodeVisitor]
+ /// It performs a depth first walk of an node and its children.
+ ///
+ /// For an node tree such as
+ /// ```text
+ /// ParentNode
+ /// left: ChildNode1
+ /// right: ChildNode2
+ /// ```
+ ///
+ /// The nodes are visited using the following order
+ /// ```text
+ /// pre_visit(ParentNode)
+ /// pre_visit(ChildNode1)
+ /// post_visit(ChildNode1)
+ /// pre_visit(ChildNode2)
+ /// post_visit(ChildNode2)
+ /// post_visit(ParentNode)
+ /// ```
+ ///
+ /// If an Err result is returned, recursion is stopped immediately
+ ///
+ /// If [`Recursion::Stop`] is returned on a call to pre_visit, no
+ /// children of that node will be visited, nor is post_visit
+ /// called on that node
+ ///
+ /// If using the default [`post_visit`] with nothing to do, the [`collect`] should be preferred
+ fn visit<V: TreeNodeVisitor<N = Self>>(&self, visitor: &mut V) -> Result<Recursion> {
+ match visitor.pre_visit(self)? {
+ Recursion::Continue => {}
+ // If the recursion should stop, do not visit children
+ Recursion::Stop => return Ok(Recursion::Stop),
+ r => {
+ return Err(DataFusionError::Execution(format!(
+ "Recursion {r:?} is not supported for collect_using"
+ )))
+ }
+ };
+
+ for child in self.get_children() {
+ match child.visit(visitor)? {
+ Recursion::Continue => {}
+ // If the recursion should stop, do not visit children
+ Recursion::Stop => return Ok(Recursion::Stop),
+ r => {
+ return Err(DataFusionError::Execution(format!(
+ "Recursion {r:?} is not supported for collect_using"
+ )))
+ }
+ }
+ }
+
+ visitor.post_visit(self)
+ }
+
+ /// Convenience utils for writing optimizers rule: recursively apply the given `op` to the node tree.
+ /// When `op` does not apply to a given node, it is left unchanged.
+ /// The default tree traversal direction is transform_up(Postorder Traversal).
+ fn transform<F>(self, op: &F) -> Result<Self>
+ where
+ F: Fn(Self) -> Result<Option<Self>>,
+ {
+ self.transform_up(op)
+ }
+
+ /// Convenience utils for writing optimizers rule: recursively apply the given 'op' to the node and all of its
+ /// children(Preorder Traversal).
+ /// When the `op` does not apply to a given node, it is left unchanged.
+ fn transform_down<F>(self, op: &F) -> Result<Self>
+ where
+ F: Fn(Self) -> Result<Option<Self>>,
+ {
+ let node_cloned = self.clone();
+ let after_op = match op(node_cloned)? {
+ Some(value) => value,
+ None => self,
+ };
+ after_op.map_children(|node| node.transform_down(op))
+ }
+
+ /// Convenience utils for writing optimizers rule: recursively apply the given 'op' first to all of its
+ /// children and then itself(Postorder Traversal).
+ /// When the `op` does not apply to a given node, it is left unchanged.
+ fn transform_up<F>(self, op: &F) -> Result<Self>
+ where
+ F: Fn(Self) -> Result<Option<Self>>,
+ {
+ let after_op_children = self.map_children(|node| node.transform_up(op))?;
+
+ let after_op_children_clone = after_op_children.clone();
+ let new_node = match op(after_op_children)? {
+ Some(value) => value,
+ None => after_op_children_clone,
+ };
+ Ok(new_node)
+ }
+
+ /// Transform the tree node using the given [TreeNodeRewriter]
+ /// It performs a depth first walk of an node and its children.
+ ///
+ /// For an node tree such as
+ /// ```text
+ /// ParentNode
+ /// left: ChildNode1
+ /// right: ChildNode2
+ /// ```
+ ///
+ /// The nodes are visited using the following order
+ /// ```text
+ /// pre_visit(ParentNode)
+ /// pre_visit(ChildNode1)
+ /// mutate(ChildNode1)
+ /// pre_visit(ChildNode2)
+ /// mutate(ChildNode2)
+ /// mutate(ParentNode)
+ /// ```
+ ///
+ /// If an Err result is returned, recursion is stopped immediately
+ ///
+ /// If [`false`] is returned on a call to pre_visit, no
+ /// children of that node will be visited, nor is mutate
+ /// called on that node
+ ///
+ /// If using the default [`pre_visit`] with [`true`] returned, the [`transform`] should be preferred
+ fn rewrite<R: TreeNodeRewriter<N = Self>>(self, rewriter: &mut R) -> Result<Self> {
+ let need_mutate = match rewriter.pre_visit(&self)? {
+ Recursion::Mutate => return rewriter.mutate(self),
+ Recursion::Stop => return Ok(self),
+ Recursion::Continue => true,
+ Recursion::Skip => false,
+ };
+
+ let after_op_children = self.map_children(|node| node.rewrite(rewriter))?;
+
+ // now rewrite this node itself
+ if need_mutate {
+ rewriter.mutate(after_op_children)
+ } else {
+ Ok(after_op_children)
+ }
+ }
+
+ /// Apply transform `F` to the node's children, the transform `F` might have a direction(Preorder or Postorder)
+ fn map_children<F>(self, transform: F) -> Result<Self>
+ where
+ F: FnMut(Self) -> Result<Self>;
+}
+
+/// Implements the [visitor
+/// pattern](https://en.wikipedia.org/wiki/Visitor_pattern) for recursively walking [`TreeNode`]s.
+///
+/// [`TreeNodeVisitor`] allows keeping the algorithms
+/// separate from the code to traverse the structure of the `TreeNode`
+/// tree and makes it easier to add new types of tree node and
+/// algorithms by.
Review Comment:
```suggestion
/// algorithms.
```
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