sligtly adapt default reader

crates/polars-core/src/config.rs

@@ -28,10 +28,3 @@ pub(crate) fn decimal_is_active() -> bool {
 pub fn verbose() -> bool {
     std::env::var("POLARS_VERBOSE").as_deref().unwrap_or("") == "1"
 }
-
-pub fn concurrent_download_limit() -> usize {
-    std::env::var("POLARS_CONC_DOWNLOAD_LIMIT")
-        .ok()
-        .and_then(|v| v.parse::<usize>().ok())
-        .unwrap_or(64)
-}

crates/polars-lazy/src/physical_plan/executors/scan/parquet.rs

@@ -1,6 +1,6 @@
 use std::path::{Path, PathBuf};
 
-use polars_core::config::{concurrent_download_limit, verbose};
+use polars_core::config::verbose;
 use polars_core::utils::accumulate_dataframes_vertical;
 use polars_io::cloud::CloudOptions;
 use polars_io::parquet::FileMetaData;
@@ -165,25 +165,7 @@ impl ParquetExec {
         let cloud_options = self.cloud_options.as_ref();
 
         let mut result = vec![];
-        let batch_size = if let Some(md) = self.metadata.as_ref() {
-            let n_columns = self
-                .file_options
-                .with_columns
-                .as_ref()
-                .map(|opt| opt.len())
-                .unwrap_or(first_schema.len());
-            let concurrent_per_file = md.row_groups.len() * n_columns;
-            if verbose {
-                eprintln!(
-                    "estimated concurrent downloads per file: {}",
-                    concurrent_per_file
-                );
-            }
-            concurrent_download_limit() / concurrent_per_file + 1
-        } else {
-            std::cmp::min(POOL.current_num_threads(), 16)
-        };
-
+        let batch_size = 5;
         let mut remaining_rows_to_read = self.file_options.n_rows.unwrap_or(usize::MAX);
         let mut base_row_count = self.file_options.row_count.take();
         let mut processed = 0;