[Benchmarks] Make partitions default to number of cores instead of 2 (#8292)

* Default partitions to num cores

* update test

Author: andygrove

benchmarks/src/sort.rs

@@ -148,8 +148,9 @@ impl RunOpt {
             println!("Executing '{title}' (sorting by: {expr:?})");
             rundata.start_new_case(title);
             for i in 0..self.common.iterations {
-                let config =
-                    SessionConfig::new().with_target_partitions(self.common.partitions);
+                let config = SessionConfig::new().with_target_partitions(
+                    self.common.partitions.unwrap_or(num_cpus::get()),
+                );
                 let ctx = SessionContext::new_with_config(config);
                 let (rows, elapsed) =
                     exec_sort(&ctx, &expr, &test_file, self.common.debug).await?;

benchmarks/src/tpch/run.rs

@@ -285,7 +285,7 @@ impl RunOpt {
     }
 
     fn partitions(&self) -> usize {
-        self.common.partitions
+        self.common.partitions.unwrap_or(num_cpus::get())
     }
 }
 
@@ -325,7 +325,7 @@ mod tests {
         let path = get_tpch_data_path()?;
         let common = CommonOpt {
             iterations: 1,
-            partitions: 2,
+            partitions: Some(2),
             batch_size: 8192,
             debug: false,
         };
@@ -357,7 +357,7 @@ mod tests {
         let path = get_tpch_data_path()?;
         let common = CommonOpt {
             iterations: 1,
-            partitions: 2,
+            partitions: Some(2),
             batch_size: 8192,
             debug: false,
         };

benchmarks/src/util/options.rs

@@ -26,9 +26,9 @@ pub struct CommonOpt {
     #[structopt(short = "i", long = "iterations", default_value = "3")]
     pub iterations: usize,
 
-    /// Number of partitions to process in parallel
-    #[structopt(short = "n", long = "partitions", default_value = "2")]
-    pub partitions: usize,
+    /// Number of partitions to process in parallel. Defaults to number of available cores.
+    #[structopt(short = "n", long = "partitions")]
+    pub partitions: Option<usize>,
 
     /// Batch size when reading CSV or Parquet files
     #[structopt(short = "s", long = "batch-size", default_value = "8192")]
@@ -48,7 +48,7 @@ impl CommonOpt {
     /// Modify the existing config appropriately
     pub fn update_config(&self, config: SessionConfig) -> SessionConfig {
         config
-            .with_target_partitions(self.partitions)
+            .with_target_partitions(self.partitions.unwrap_or(num_cpus::get()))
             .with_batch_size(self.batch_size)
     }
 }