[GitHub] [arrow-datafusion] alamb commented on a diff in pull request #7425: New interface for `get_scan_files` to break dependency

["alamb (via GitHub)" <gi...@apache.org>]

alamb commented on code in PR #7425:
URL: https://github.com/apache/arrow-datafusion/pull/7425#discussion_r1316371984


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datafusion/core/src/datasource/physical_plan/finder.rs:
##########
@@ -0,0 +1,114 @@
+// 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.
+
+//! [`PartitionedFileFinder`] to scan [`ExecutionPlan`]` for input
+//! partitioned file sources.
+
+use std::sync::Arc;
+
+use datafusion_common::{
+    tree_node::{TreeNode, VisitRecursion},
+    Result,
+};
+
+use crate::{datasource::listing::PartitionedFile, physical_plan::ExecutionPlan};
+
+use super::{AvroExec, CsvExec, NdJsonExec, ParquetExec};
+
+pub type FinderFunction =
+    Box<dyn Fn(&dyn ExecutionPlan) -> Option<Vec<Vec<PartitionedFile>>>>;
+
+/// Get all of the [`PartitionedFile`] to be scanned for an [`ExecutionPlan`]
+///
+/// This structure will find all `ScanFileConfig` in any built in
+/// [`ExecutionPlan`] and allows finding user defined nodes as well
+pub struct PartitionedFileFinder {
+    custom_finder: FinderFunction,
+}
+
+impl Default for PartitionedFileFinder {
+    fn default() -> Self {
+        Self {
+            // default custom finding function does nothing
+            custom_finder: Box::new(|_plan| None),
+        }
+    }
+}
+
+impl PartitionedFileFinder {
+    /// Create a new file finder
+    pub fn new() -> Self {
+        Default::default()
+    }
+
+    /// Get all [`PartitionedFile`]s that are scanned for an
+    /// [`ExecutionPlan`],  by recursively checking all children
+    pub fn find(&self, plan: Arc<dyn ExecutionPlan>) -> Vec<Vec<Vec<PartitionedFile>>> {
+        let mut collector: Vec<Vec<Vec<PartitionedFile>>> = vec![];
+        plan.apply(&mut |plan| {
+            if let Some(files) = self.get_files(plan.as_ref()) {
+                collector.push(files);
+            }
+            Ok(VisitRecursion::Continue)
+        })
+        .expect("infallable");
+        collector
+    }
+
+    /// Provide a custom method to find `PartitionedFiles` for
+    /// `ExecutionPlans`
+    ///
+    /// Called on all [`ExecutionPlan`]s other than built ins such as
+    /// [`ParquetExec`] and can be used to extract
+    /// [`PartitionedFile`]s from user defined nodes
+    pub fn with_finder<F>(mut self, custom_finder: F) -> Self
+    where
+        F: Fn(&dyn ExecutionPlan) -> Option<Vec<Vec<PartitionedFile>>> + 'static,
+    {
+        self.custom_finder = Box::new(custom_finder);
+        self
+    }
+
+    /// Return the [`PartitionedFile`] scanned by this plan node, or
+    /// `None` if the plan does not can files
+    fn get_files(&self, plan: &dyn ExecutionPlan) -> Option<Vec<Vec<PartitionedFile>>> {
+        let plan_any = plan.as_any();
+        if let Some(parquet_exec) = plan_any.downcast_ref::<ParquetExec>() {
+            Some(parquet_exec.base_config().file_groups.clone())
+        } else if let Some(avro_exec) = plan_any.downcast_ref::<AvroExec>() {
+            Some(avro_exec.base_config().file_groups.clone())
+        } else if let Some(json_exec) = plan_any.downcast_ref::<NdJsonExec>() {
+            Some(json_exec.base_config().file_groups.clone())
+        } else if let Some(csv_exec) = plan_any.downcast_ref::<CsvExec>() {
+            Some(csv_exec.base_config().file_groups.clone())
+        } else {
+            (self.custom_finder)(plan)
+        }

Review Comment:
   I agree it is ugly 
   
   However, the API in this PR is extensible in the sense that it can handle any new user defined execution plan (the test contains an example of doing so). 
   
   Also I don't think this PR prevents feature gating, as @tustvold  explains in https://github.com/apache/arrow-datafusion/issues/7357#issuecomment-1707193574
   
   However it is ugly, as you say



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