[GitHub] [arrow] houqp commented on a change in pull request #7210: ARROW-8839: [Rust] [DataFusion] support CSV schema inference in logical plan

[GitBox <gi...@apache.org>]

houqp commented on a change in pull request #7210:
URL: https://github.com/apache/arrow/pull/7210#discussion_r427602640



##########
File path: rust/datafusion/src/execution/physical_plan/csv.rs
##########
@@ -71,15 +75,35 @@ impl CsvExec {
     /// Create a new execution plan for reading a set of CSV files
     pub fn try_new(
         path: &str,
-        schema: Arc<Schema>,
+        schema: Option<Arc<Schema>>,
         has_header: bool,
+        delimiter: Option<u8>,
         projection: Option<Vec<usize>>,
         batch_size: usize,
     ) -> Result<Self> {
+        let schema = match schema {
+            Some(s) => s,
+            None => {
+                let mut filenames: Vec<String> = vec![];
+                common::build_file_list(path, &mut filenames, ".csv")?;
+                if filenames.is_empty() {
+                    return Err(ExecutionError::General("No files found".to_string()));
+                }
+
+                let f = File::open(&filenames[0])?;
+                Arc::new(csv::infer_file_schema(
+                    &mut BufReader::new(f),
+                    delimiter.unwrap_or(b','),
+                    Some(30),

Review comment:
       good catch, will change to 1000, that 30 was a number i used for debugging purpose, forgot to change it back :P




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