Consolidate external dependency examples (#18142) (#18747)

## Which issue does this PR close?

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- part of ##18142.

## Rationale for this change
This PR is for consolidating all the `external_dependency` examples
(dataframe_to_s3, query_aws_s3) into a single example binary. We are
agreed on the pattern and we can apply it to the remaining examples

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---------

Co-authored-by: Sergey Zhukov <[email protected]>

Author: cj-zhukov

datafusion-examples/Cargo.toml

@@ -35,14 +35,6 @@ rust-version = { workspace = true }
 [lints]
 workspace = true
 
-[[example]]
-name = "dataframe_to_s3"
-path = "examples/external_dependency/dataframe-to-s3.rs"
-
-[[example]]
-name = "query_aws_s3"
-path = "examples/external_dependency/query-aws-s3.rs"
-
 [dev-dependencies]
 arrow = { workspace = true }
 # arrow_schema is required for record_batch! macro :sad:

datafusion-examples/README.md

@@ -60,8 +60,8 @@ cargo run --example dataframe -- dataframe
 - [`examples/custom_data_source/custom_datasource.rs`](examples/custom_data_source/custom_datasource.rs): Run queries against a custom datasource (TableProvider)
 - [`examples/custom_data_source/custom_file_casts.rs`](examples/custom_data_source/custom_file_casts.rs): Implement custom casting rules to adapt file schemas
 - [`examples/custom_data_source/custom_file_format.rs`](examples/custom_data_source/custom_file_format.rs): Write data to a custom file format
-- [`dataframe-to-s3.rs`](examples/external_dependency/dataframe-to-s3.rs): Run a query using a DataFrame against a parquet file from s3 and writing back to s3
-- [`examples/dataframe/dataframe.rs`](examples/dataframe/dataframe.rs): Run a query using a DataFrame API against parquet files, csv files, and in-memory data, including multiple subqueries. Also demonstrates the various methods to write out a DataFrame to a table, parquet file, csv file, and json file.
+- [`examples/external_dependency/dataframe_to_s3.rs`](examples/external_dependency/dataframe_to_s3.rs): Run a query using a DataFrame against a parquet file from s3 and writing back to s3
+- [`dataframe.rs`](examples/dataframe.rs): Run a query using a DataFrame API against parquet files, csv files, and in-memory data, including multiple subqueries. Also demonstrates the various methods to write out a DataFrame to a table, parquet file, csv file, and json file.
 - [`examples/builtin_functions/date_time`](examples/builtin_functions/date_time.rs): Examples of date-time related functions and queries
 - [`examples/custom_data_source/default_column_values.rs`](examples/custom_data_source/default_column_values.rs): Implement custom default value handling for missing columns using field metadata and PhysicalExprAdapter
 - [`examples/dataframe/deserialize_to_struct.rs`](examples/dataframe/deserialize_to_struct.rs): Convert query results (Arrow ArrayRefs) into Rust structs
@@ -83,7 +83,7 @@ cargo run --example dataframe -- dataframe
 - [`examples/query_planning/planner_api.rs`](examples/query_planning/planner_api.rs) APIs to manipulate logical and physical plans
 - [`examples/query_planning/pruning.rs`](examples/query_planning/pruning.rs): Use pruning to rule out files based on statistics
 - [`examples/query_planning/thread_pools.rs`](examples/query_planning/thread_pools.rs): Demonstrates TrackConsumersPool for memory tracking and debugging with enhanced error messages and shows how to implement memory-aware ExecutionPlan with memory reservation and spilling
-- [`query-aws-s3.rs`](examples/external_dependency/query-aws-s3.rs): Configure `object_store` and run a query against files stored in AWS S3
+- [`examples/external_dependency/query_aws_s3.rs`](examples/external_dependency/query_aws_s3.rs): Configure `object_store` and run a query against files stored in AWS S3
 - [`examples/data_io/query_http_csv.rs`](examples/data_io/query_http_csv.rs): Configure `object_store` and run a query against files via HTTP
 - [`examples/builtin_functions/regexp.rs`](examples/builtin_functions/regexp.rs): Examples of using regular expression functions
 - [`examples/data_io/remote_catalog.rs`](examples/data_io/remote_catalog.rs): Examples of interfacing with a remote catalog (e.g. over a network)

…s/external_dependency/dataframe-to-s3.rs …s/external_dependency/dataframe_to_s3.rsdatafusion-examples/examples/external_dependency/dataframe-to-s3.rs renamed to datafusion-examples/examples/external_dependency/dataframe_to_s3.rs datafusion-examples/examples/external_dependency/dataframe-to-s3.rs renamed to datafusion-examples/examples/external_dependency/dataframe_to_s3.rs

@@ -15,6 +15,8 @@
 // specific language governing permissions and limitations
 // under the License.
 
+//! See `main.rs` for how to run it.
+
 use std::env;
 use std::sync::Arc;
 
@@ -28,14 +30,18 @@ use datafusion::prelude::*;
 use object_store::aws::AmazonS3Builder;
 use url::Url;
 
-/// This example demonstrates querying data from AmazonS3 and writing
-/// the result of a query back to AmazonS3
-#[tokio::main]
-async fn main() -> Result<()> {
+/// This example demonstrates querying data from Amazon S3 and writing
+/// the result of a query back to Amazon S3.
+///
+/// The following environment variables must be defined:
+///
+/// - AWS_ACCESS_KEY_ID
+/// - AWS_SECRET_ACCESS_KEY
+pub async fn dataframe_to_s3() -> Result<()> {
     // create local execution context
     let ctx = SessionContext::new();
 
-    //enter region and bucket to which your credentials have GET and PUT access
+    // enter region and bucket to which your credentials have GET and PUT access
     let region = "<bucket-region-here>";
     let bucket_name = "<bucket-name-here>";
 
@@ -66,13 +72,13 @@ async fn main() -> Result<()> {
         .write_parquet(&out_path, DataFrameWriteOptions::new(), None)
         .await?;
 
-    //write as JSON to s3
+    // write as JSON to s3
     let json_out = format!("s3://{bucket_name}/json_out");
     df.clone()
         .write_json(&json_out, DataFrameWriteOptions::new(), None)
         .await?;
 
-    //write as csv to s3
+    // write as csv to s3
     let csv_out = format!("s3://{bucket_name}/csv_out");
     df.write_csv(&csv_out, DataFrameWriteOptions::new(), None)
         .await?;

datafusion-examples/examples/external_dependency/main.rs

@@ -0,0 +1,93 @@
+// 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.
+
+//! # These are using data from Amazon S3 examples
+//!
+//! These examples demonstrate how to work with data from Amazon S3.
+//!
+//! ## Usage
+//! ```bash
+//! cargo run --example external_dependency -- [dataframe_to_s3|query_aws_s3]
+//! ```
+//!
+//! Each subcommand runs a corresponding example:
+//! - `dataframe_to_s3` — run a query using a DataFrame against a parquet file from AWS S3 and writing back to AWS S3
+//! - `query_aws_s3` — configure `object_store` and run a query against files stored in AWS S3
+
+mod dataframe_to_s3;
+mod query_aws_s3;
+
+use std::str::FromStr;
+
+use datafusion::error::{DataFusionError, Result};
+
+enum ExampleKind {
+    DataframeToS3,
+    QueryAwsS3,
+}
+
+impl AsRef<str> for ExampleKind {
+    fn as_ref(&self) -> &str {
+        match self {
+            Self::DataframeToS3 => "dataframe_to_s3",
+            Self::QueryAwsS3 => "query_aws_s3",
+        }
+    }
+}
+
+impl FromStr for ExampleKind {
+    type Err = DataFusionError;
+
+    fn from_str(s: &str) -> Result<Self> {
+        match s {
+            "dataframe_to_s3" => Ok(Self::DataframeToS3),
+            "query_aws_s3" => Ok(Self::QueryAwsS3),
+            _ => Err(DataFusionError::Execution(format!("Unknown example: {s}"))),
+        }
+    }
+}
+
+impl ExampleKind {
+    const ALL: [Self; 2] = [Self::DataframeToS3, Self::QueryAwsS3];
+
+    const EXAMPLE_NAME: &str = "external_dependency";
+
+    fn variants() -> Vec<&'static str> {
+        Self::ALL.iter().map(|x| x.as_ref()).collect()
+    }
+}
+
+#[tokio::main]
+async fn main() -> Result<()> {
+    let usage = format!(
+        "Usage: cargo run --example {} -- [{}]",
+        ExampleKind::EXAMPLE_NAME,
+        ExampleKind::variants().join("|")
+    );
+
+    let arg = std::env::args().nth(1).ok_or_else(|| {
+        eprintln!("{usage}");
+        DataFusionError::Execution("Missing argument".to_string())
+    })?;
+
+    match arg.parse::<ExampleKind>()? {
+        ExampleKind::DataframeToS3 => dataframe_to_s3::dataframe_to_s3().await?,
+        ExampleKind::QueryAwsS3 => query_aws_s3::query_aws_s3().await?,
+    }
+
+    Ok(())
+}

…ples/external_dependency/query-aws-s3.rs …ples/external_dependency/query_aws_s3.rsdatafusion-examples/examples/external_dependency/query-aws-s3.rs renamed to datafusion-examples/examples/external_dependency/query_aws_s3.rs datafusion-examples/examples/external_dependency/query-aws-s3.rs renamed to datafusion-examples/examples/external_dependency/query_aws_s3.rs

@@ -15,21 +15,22 @@
 // specific language governing permissions and limitations
 // under the License.
 
+//! See `main.rs` for how to run it.
+
 use datafusion::error::Result;
 use datafusion::prelude::*;
 use object_store::aws::AmazonS3Builder;
 use std::env;
 use std::sync::Arc;
 use url::Url;
 
-/// This example demonstrates querying data in an S3 bucket.
+/// This example demonstrates querying data in a public S3 bucket
+/// (the NYC TLC open dataset: `s3://nyc-tlc`).
 ///
 /// The following environment variables must be defined:
-///
-/// - AWS_ACCESS_KEY_ID
-/// - AWS_SECRET_ACCESS_KEY
-#[tokio::main]
-async fn main() -> Result<()> {
+/// - `AWS_ACCESS_KEY_ID`
+/// - `AWS_SECRET_ACCESS_KEY`
+pub async fn query_aws_s3() -> Result<()> {
     let ctx = SessionContext::new();
 
     // the region must be set to the region where the bucket exists until the following