feat: add parquet examples to the readme

Author: clflushopt

README.md

@@ -15,27 +15,22 @@ using the [tpchgen](https://github.com/clflushopt/tpchgen-rs) crates.
 
 ## Usage
 
-The `datafusion-tpch` crate offers two possible ways to register the TPCH individual
-table functions.
+The `datafusion-tpch` crate offers two possible ways to register the TPCH table
+functions.
 
-You can register functions individually.
+You can register the individual udtfs separately.
 
 ```rust
+use datafusion_tpch::register_tpch_udtfs;
+
 #[tokio::main]
 async fn main() -> Result<()> {
     // create local execution context
     let ctx = SessionContext::new();
 
     // Register all the UDTFs.
-    ctx.register_udtf(TpchNation::name(), Arc::new(TpchNation {}));
-    ctx.register_udtf(TpchCustomer::name(), Arc::new(TpchCustomer {}));
-    ctx.register_udtf(TpchOrders::name(), Arc::new(TpchOrders {}));
-    ctx.register_udtf(TpchLineitem::name(), Arc::new(TpchLineitem {}));
-    ctx.register_udtf(TpchPart::name(), Arc::new(TpchPart {}));
-    ctx.register_udtf(TpchPartsupp::name(), Arc::new(TpchPartsupp {}));
-    ctx.register_udtf(TpchSupplier::name(), Arc::new(TpchSupplier {}));
-    ctx.register_udtf(TpchRegion::name(), Arc::new(TpchRegion {}));
- 
+    register_tpch_udtfs(&ctx);
+
     // Generate the nation table with a scale factor of 1.
     let df = ctx
         .sql(format!("SELECT * FROM tpch_nation(1.0);").as_str())
@@ -45,8 +40,7 @@ async fn main() -> Result<()> {
 }
 ```
 
-Or use the helper function `register_tpch_udtfs` to register all of them
-at once (which is the preferred approach).
+Or you can register a single UDTF which generates all tables at once.
 
 ```rust
 use datafusion_tpch::register_tpch_udtfs;
@@ -57,17 +51,60 @@ async fn main() -> Result<()> {
     let ctx = SessionContext::new();
 
     // Register all the UDTFs.
-    register_tpch_udtfs(&ctx);
+    register_tpch_udtf(&ctx);
 
     // Generate the nation table with a scale factor of 1.
     let df = ctx
-        .sql(format!("SELECT * FROM tpch_nation(1.0);").as_str())
+        .sql(format!("SELECT * FROM tpch(1.0);").as_str())
         .await?;
     df.show().await?;
     Ok(())
 }
 ```
 
+## Examples
+
+To keep things simple we don't bundle writing to parquet in the table provider
+but instead defer that to the user who can use the `COPY` command.
+
+
+```rust
+use datafusion::prelude::{SessionConfig, SessionContext};
+use datafusion_tpch::{register_tpch_udtf, register_tpch_udtfs};
+
+#[tokio::main]
+async fn main() -> datafusion::error::Result<()> {
+    let ctx = SessionContext::new_with_config(SessionConfig::new().with_information_schema(true));
+    register_tpch_udtf(&ctx);
+
+    let sql_df = ctx.sql(&format!("SELECT * FROM tpch(1.0);")).await?;
+    sql_df.show().await?;
+
+    let sql_df = ctx.sql(&format!("SHOW TABLES;")).await?;
+    sql_df.show().await?;
+
+    let sql_df = ctx
+        .sql(&format!(
+            "COPY nation TO './tpch_nation.parquet' STORED AS PARQUET"
+        ))
+        .await?;
+    sql_df.show().await?;
+
+    register_tpch_udtfs(&ctx)?;
+
+    let sql_df = ctx
+        .sql(&format!(
+            "COPY (SELECT * FROM tpch_lineitem(1.0)) TO './tpch_lineitem_sf_10.parquet' STORED AS PARQUET"
+        ))
+        .await?;
+    sql_df.show().await?;
+
+    Ok(())
+}
+```
+
+You can find other examples in the [examples](examples/) directory.
+
 ## License
 
-The project is licensed under the [APACHE 2.0](LICENSE) license.
+The project is licensed under the [APACHE 2.0](LICENSE) license.

examples/parquet.rs

@@ -1,6 +1,5 @@
 //! Example of using the datafusion-tpch extension to generate TPCH tables
 //! and writing them to disk via `COPY`.
-
 use datafusion::prelude::{SessionConfig, SessionContext};
 use datafusion_tpch::{register_tpch_udtf, register_tpch_udtfs};
 

src/lib.rs

@@ -33,15 +33,8 @@ macro_rules! define_tpch_udtf_provider {
         /// async fn main() -> Result<(), Error> {
         ///     // create local execution context
         ///     let ctx = SessionContext::new();
-        ///     // Register all the UDTFs.
-        ///     ctx.register_udtf(TpchNation::name(), Arc::new(TpchNation {}));
-        ///     ctx.register_udtf(TpchCustomer::name(), Arc::new(TpchCustomer {}));
-        ///     ctx.register_udtf(TpchOrders::name(), Arc::new(TpchOrders {}));
-        ///     ctx.register_udtf(TpchLineitem::name(), Arc::new(TpchLineitem {}));
-        ///     ctx.register_udtf(TpchPart::name(), Arc::new(TpchPart {}));
-        ///     ctx.register_udtf(TpchPartsupp::name(), Arc::new(TpchPartsupp {}));
-        ///     ctx.register_udtf(TpchSupplier::name(), Arc::new(TpchSupplier {}));
-        ///     ctx.register_udtf(TpchRegion::name(), Arc::new(TpchRegion {}));
+        ///     // Register all udtfs.
+        ///     register_tpch_udtfs(&ctx);
         ///     // Generate the nation table with a scale factor of 1.
         ///     let df = ctx
         ///         .sql(format!("SELECT * FROM tpch_nation(1.0);").as_str())