From b03d1ad1cf4ebb5a8a854a09f31b797ae64fc16c Mon Sep 17 00:00:00 2001
From: "R. Tyler Croy" <rtyler@brokenco.de>
Date: Wed, 4 Jan 2023 21:06:52 -0800
Subject: [PATCH] Demonstrate converting a Schema to an ArrowSchema and
 avoiding the pass of a writer to convert_to_batch

---
 src/main.rs | 78 ++++++++++++++++++++++++++++-------------------------
 1 file changed, 42 insertions(+), 36 deletions(-)

diff --git a/src/main.rs b/src/main.rs
index bcfcc6d..c3e61b0 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -54,7 +54,7 @@ async fn main() -> Result<(), anyhow::Error> {
         RecordBatchWriter::for_table(&table).expect("Failed to make RecordBatchWriter");
 
     let records = fetch_readings();
-    let batch = convert_to_batch(&writer, &records);
+    let batch = convert_to_batch(&records);
 
     writer.write(batch).await?;
 
@@ -67,39 +67,6 @@ async fn main() -> Result<(), anyhow::Error> {
     Ok(())
 }
 
-/*
- * Pilfered from writer/test_utils.rs in delta-rs
- */
-async fn create_initialized_table(table_path: &Path) -> DeltaTable {
-    let mut table = DeltaTableBuilder::from_uri(table_path.to_str().unwrap())
-        .build()
-        .unwrap();
-    let table_schema = WeatherRecord::schema();
-    let mut commit_info = serde_json::Map::<String, serde_json::Value>::new();
-    commit_info.insert(
-        "operation".to_string(),
-        serde_json::Value::String("CREATE TABLE".to_string()),
-    );
-    commit_info.insert(
-        "userName".to_string(),
-        serde_json::Value::String("test user".to_string()),
-    );
-
-    let protocol = Protocol {
-        min_reader_version: 1,
-        min_writer_version: 1,
-    };
-
-    let metadata = DeltaTableMetaData::new(None, None, None, table_schema, vec![], HashMap::new());
-
-    table
-        .create(metadata, protocol, Some(commit_info), None)
-        .await
-        .unwrap();
-
-    table
-}
-
 // Creating a simple type alias for improved readability
 type Fahrenheit = i32;
 
@@ -193,7 +160,12 @@ fn fetch_readings() -> Vec<WeatherRecord> {
  *  transformation is quite tricky in Rust, whereas in Python or another loosely
  *  typed language it might be simpler.
  */
-fn convert_to_batch(writer: &RecordBatchWriter, records: &Vec<WeatherRecord>) -> RecordBatch {
+fn convert_to_batch(records: &Vec<WeatherRecord>) -> RecordBatch {
+    let schema = WeatherRecord::schema();
+    let arrow_schema = <deltalake::arrow::datatypes::Schema as TryFrom<&Schema>>::try_from(&schema)
+        .expect("Failed to convert schema tro ArrowSchema");
+    let arrow_schema_ref = Arc::new(arrow_schema);
+
     let mut ts = vec![];
     let mut temp = vec![];
     let mut lat = vec![];
@@ -213,7 +185,41 @@ fn convert_to_batch(writer: &RecordBatchWriter, records: &Vec<WeatherRecord>) ->
         Arc::new(Float64Array::from(long)),
     ];
 
-    RecordBatch::try_new(writer.arrow_schema(), arrow_array).expect("Failed to create RecordBatch")
+    RecordBatch::try_new(arrow_schema_ref, arrow_array).expect("Failed to create RecordBatch")
+}
+
+/*
+ * Pilfered from writer/test_utils.rs in delta-rs. This code will basically create a new Delta
+ * Table in an existing directory that doesn't currently contain a Delta table
+ */
+async fn create_initialized_table(table_path: &Path) -> DeltaTable {
+    let mut table = DeltaTableBuilder::from_uri(table_path.to_str().unwrap())
+        .build()
+        .unwrap();
+    let table_schema = WeatherRecord::schema();
+    let mut commit_info = serde_json::Map::<String, serde_json::Value>::new();
+    commit_info.insert(
+        "operation".to_string(),
+        serde_json::Value::String("CREATE TABLE".to_string()),
+    );
+    commit_info.insert(
+        "userName".to_string(),
+        serde_json::Value::String("test user".to_string()),
+    );
+
+    let protocol = Protocol {
+        min_reader_version: 1,
+        min_writer_version: 1,
+    };
+
+    let metadata = DeltaTableMetaData::new(None, None, None, table_schema, vec![], HashMap::new());
+
+    table
+        .create(metadata, protocol, Some(commit_info), None)
+        .await
+        .unwrap();
+
+    table
 }
 
 #[cfg(test)]