Function sqlite_date_trunc_to_sql

datafusion/sql/src/unparser/utils.rs:573–605

SQLite does not support timestamp/date scalars like `to_timestamp`, `from_unixtime`, `date_trunc`, etc. This uses the `strftime` function to format the timestamp as a string depending on the truncation unit. # Errors - If the number of arguments is not 2 - truncation unit and the column or expression to convert. - If the scalar function cannot be converted to SQL.

(
    unparser: &Unparser,
    date_trunc_args: &[Expr],
)

/// - If the number of arguments is not 2 - truncation unit and the column or expression to convert.
/// - If the scalar function cannot be converted to SQL.
pub(crate) fn sqlite_date_trunc_to_sql(
    unparser: &Unparser,
    date_trunc_args: &[Expr],
) -> Result<Option<ast::Expr>> {
    assert_eq_or_internal_err!(
        date_trunc_args.len(),
        2,
        "date_trunc for SQLite expects 2 arguments, found {}",
        date_trunc_args.len()
    );

    if let Expr::Literal(ScalarValue::Utf8(Some(unit)), _) = &date_trunc_args[0] {
        let format = match unit.to_lowercase().as_str() {
            "year" => "%Y",
            "month" => "%Y-%m",
            "day" => "%Y-%m-%d",
            "hour" => "%Y-%m-%d %H",
            "minute" => "%Y-%m-%d %H:%M",
            "second" => "%Y-%m-%d %H:%M:%S",
            _ => return Ok(None),
        };

        return Ok(Some(unparser.scalar_function_to_sql(
            "strftime",
            &[
                Expr::Literal(ScalarValue::Utf8(Some(format.to_string())), None),
                date_trunc_args[1].clone(),
            ],
        )?));
    }

    Ok(None)
}