datafusion-examples/examples/builtin_functions/main.rs

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//! # These are miscellaneous function-related examples
//!
//! These examples demonstrate miscellaneous function-related features.
//!
//! ## Usage
//! ```bash
//! cargo run --example builtin_functions -- [date_time|function_factory|regexp]
//! ```
//!
//! Each subcommand runs a corresponding example:
//! - `date_time` — examples of date-time related functions and queries
//! - `function_factory` — register `CREATE FUNCTION` handler to implement SQL macros
//! - `regexp` — examples of using regular expression functions

mod date_time;
mod function_factory;
mod regexp;

use std::str::FromStr;

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

enum ExampleKind {
    DateTime,
    FunctionFactory,
    Regexp,
}

impl AsRef<str> for ExampleKind {
    fn as_ref(&self) -> &str {
        match self {
            Self::DateTime => "date_time",
            Self::FunctionFactory => "function_factory",
            Self::Regexp => "regexp",
        }
    }
}

impl FromStr for ExampleKind {
    type Err = DataFusionError;

    fn from_str(s: &str) -> Result<Self> {
        match s {
            "date_time" => Ok(Self::DateTime),
            "function_factory" => Ok(Self::FunctionFactory),
            "regexp" => Ok(Self::Regexp),
            _ => Err(DataFusionError::Execution(format!("Unknown example: {s}"))),
        }
    }
}

impl ExampleKind {
    const ALL: [Self; 3] = [Self::DateTime, Self::FunctionFactory, Self::Regexp];

    const EXAMPLE_NAME: &str = "builtin_functions";

    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::DateTime => date_time::date_time().await?,
        ExampleKind::FunctionFactory => function_factory::function_factory().await?,
        ExampleKind::Regexp => regexp::regexp().await?,
    }

    Ok(())
}