[GitHub] [arrow-datafusion] alamb commented on a diff in pull request #2969: Example that shows how to convert query result into rust struct #2959

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

alamb commented on code in PR #2969:
URL: https://github.com/apache/arrow-datafusion/pull/2969#discussion_r930957504


##########
datafusion-examples/examples/deserialize_to_struct.rs:
##########
@@ -0,0 +1,75 @@
+// 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.
+
+use datafusion::error::Result;
+use datafusion::prelude::*;
+use serde::Deserialize;
+
+/// This example shows that it is possible to convert query results into Rust structs .
+/// It will collect the query results into RecordBatch, then convert it to serde_json::Value.
+/// Then, serde_json::Value is turned into Rust's struct.
+/// Any datatype with `Deserialize` implemeneted works.
+#[tokio::main]
+async fn main() -> Result<()> {
+    let data_list = Data::new().await?;
+    println!("{:#?}", data_list);
+    Ok(())
+}
+
+#[derive(Deserialize, Debug)]
+struct Data {
+    #[allow(dead_code)]
+    int_col: i64,
+    #[allow(dead_code)]
+    double_col: f64,
+}
+
+impl Data {
+    pub async fn new() -> Result<Vec<Self>> {
+        // this group is almost the same as the one you find it in parquet_sql.rs
+        let batches = {
+            let ctx = SessionContext::new();
+
+            let testdata = datafusion::test_util::parquet_test_data();
+
+            ctx.register_parquet(
+                "alltypes_plain",
+                &format!("{}/alltypes_plain.parquet", testdata),
+                ParquetReadOptions::default(),
+            )
+            .await?;
+
+            let df = ctx
+                .sql("SELECT int_col, double_col FROM alltypes_plain")
+                .await?;
+
+            df.show().await?;
+
+            df.collect().await?
+        };
+        // converts it to serde_json type and then convert that into Rust type
+        let list =

Review Comment:
   👍  this is very cool
   
   



##########
datafusion-examples/examples/deserialize_to_struct.rs:
##########
@@ -0,0 +1,75 @@
+// 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.
+
+use datafusion::error::Result;
+use datafusion::prelude::*;
+use serde::Deserialize;
+
+/// This example shows that it is possible to convert query results into Rust structs .

Review Comment:
   👍 



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