datafusion-examples/examples/sql_ops/main.rs

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//! # SQL Examples
//!
//! These examples demonstrate SQL operations in DataFusion.
//!
//! ## Usage
//! ```bash
//! cargo run --example sql_ops -- [analysis|dialect|frontend|query]
//! ```
//!
//! Each subcommand runs a corresponding example:
//! - `analysis` — analyse SQL queries with DataFusion structures
//! - `dialect` — implementing a custom SQL dialect on top of DFParser
//! - `frontend` — create LogicalPlans (only) from sql strings
//! - `query` — query data using SQL (in memory RecordBatches, local Parquet files)

mod analysis;
mod dialect;
mod frontend;
mod query;

use std::str::FromStr;

use datafusion::error::{DataFusionError, Result};

enum ExampleKind {
    Analysis,
    Dialect,
    Frontend,
    Query,
}

impl AsRef<str> for ExampleKind {
    fn as_ref(&self) -> &str {
        match self {
            Self::Analysis => "analysis",
            Self::Dialect => "dialect",
            Self::Frontend => "frontend",
            Self::Query => "query",
        }
    }
}

impl FromStr for ExampleKind {
    type Err = DataFusionError;

    fn from_str(s: &str) -> Result<Self> {
        match s {
            "analysis" => Ok(Self::Analysis),
            "dialect" => Ok(Self::Dialect),
            "frontend" => Ok(Self::Frontend),
            "query" => Ok(Self::Query),
            _ => Err(DataFusionError::Execution(format!("Unknown example: {s}"))),
        }
    }
}

impl ExampleKind {
    const ALL: [Self; 4] = [Self::Analysis, Self::Dialect, Self::Frontend, Self::Query];

    const EXAMPLE_NAME: &str = "sql_ops";

    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::Analysis => analysis::analysis().await?,
        ExampleKind::Dialect => dialect::dialect().await?,
        ExampleKind::Frontend => frontend::frontend()?,
        ExampleKind::Query => query::query().await?,
    }

    Ok(())
}