examples/README.md

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# Ballista Examples

This directory contains examples for executing distributed queries with Ballista.

## Standalone Examples

The standalone example is the easiest to get started with. Ballista supports a standalone mode where a scheduler
and executor are started in-process.

```bash
cargo run --example standalone_sql --features="ballista/standalone"
```

### Source code for standalone SQL example

```rust
use ballista::{
    extension::SessionConfigExt,
    prelude::*
};
use datafusion::{
    execution::{options::ParquetReadOptions, SessionStateBuilder},
    prelude::{SessionConfig, SessionContext},
};

#[tokio::main]
async fn main() -> Result<()> {
    let config = SessionConfig::new_with_ballista()
        .with_target_partitions(1)
        .with_ballista_standalone_parallelism(2);

    let state = SessionStateBuilder::new()
        .with_config(config)
        .with_default_features()
        .build();

    let ctx = SessionContext::standalone_with_state(state).await?;

    let test_data = test_util::examples_test_data();

    // register parquet file with the execution context
    ctx.register_parquet(
        "test",
        &format!("{test_data}/alltypes_plain.parquet"),
        ParquetReadOptions::default(),
    )
    .await?;

    let df = ctx.sql("select count(1) from test").await?;

    df.show().await?;
    Ok(())
}

```

## Distributed Examples

For background information on the Ballista architecture, refer to
the [Ballista README](../ballista/client/README.md).

### Start a standalone cluster

From the root of the project, build release binaries.

```bash
cargo build --release
```

Start a Ballista scheduler process in a new terminal session.

```bash
RUST_LOG=info ./target/release/ballista-scheduler
```

Start one or more Ballista executor processes in new terminal sessions. When starting more than one
executor, a unique port number must be specified for each executor.

```bash
RUST_LOG=info ./target/release/ballista-executor -c 2 -p 50051
RUST_LOG=info ./target/release/ballista-executor -c 2 -p 50052
```

### Running the examples

The examples can be run using the `cargo run --bin` syntax.

### Distributed SQL Example

```bash
cargo run --release --example remote-sql
```

#### Source code for distributed SQL example

```rust
use ballista::{extension::SessionConfigExt, prelude::*};
use datafusion::{
    execution::SessionStateBuilder,
    prelude::{CsvReadOptions, SessionConfig, SessionContext},
};

/// This example demonstrates executing a simple query against an Arrow data source (CSV) and
/// fetching results, using SQL
#[tokio::main]
async fn main() -> Result<()> {
    let config = SessionConfig::new_with_ballista()
        .with_target_partitions(4)
        .with_ballista_job_name("Remote SQL Example");

    let state = SessionStateBuilder::new()
        .with_config(config)
        .with_default_features()
        .build();

    let ctx = SessionContext::remote_with_state("df://localhost:50050", state).await?;

    let test_data = test_util::examples_test_data();

    ctx.register_csv(
        "test",
        &format!("{test_data}/aggregate_test_100.csv"),
        CsvReadOptions::new(),
    )
    .await?;

    let df = ctx
        .sql(
            "SELECT c1, MIN(c12), MAX(c12) \
        FROM test \
        WHERE c11 > 0.1 AND c11 < 0.9 \
        GROUP BY c1",
        )
        .await?;

    df.show().await?;

    Ok(())
}
```

### Distributed DataFrame Example

```bash
cargo run --release --example remote-dataframe
```

#### Source code for distributed DataFrame example

```rust
use ballista::{extension::SessionConfigExt, prelude::*};
use datafusion::{
    execution::SessionStateBuilder,
    prelude::{col, lit, ParquetReadOptions, SessionConfig, SessionContext},
};

/// This example demonstrates executing a simple query against an Arrow data source (Parquet) and
/// fetching results, using the DataFrame trait
#[tokio::main]
async fn main() -> Result<()> {
    let config = SessionConfig::new_with_ballista().with_target_partitions(4);

    let state = SessionStateBuilder::new()
        .with_config(config)
        .with_default_features()
        .build();

    let ctx = SessionContext::remote_with_state("df://localhost:50050", state).await?;

    let test_data = test_util::examples_test_data();
    let filename = format!("{test_data}/alltypes_plain.parquet");

    let df = ctx
        .read_parquet(filename, ParquetReadOptions::default())
        .await?
        .select_columns(&["id", "bool_col", "timestamp_col"])?
        .filter(col("id").gt(lit(1)))?;

    df.show().await?;

    Ok(())
}
```