Method interval_to_mysql_expr

datafusion/sql/src/unparser/expr.rs:1529–1648

MySQL requires INTERVAL sql to be in the format: INTERVAL 1 YEAR + INTERVAL 1 MONTH + INTERVAL 1 DAY etc ` ` Interval sequence can't be wrapped in brackets - (INTERVAL 1 YEAR + INTERVAL 1 MONTH ...) so we need to generate a single INTERVAL expression so it works correct for interval subtraction cases MySQL supports the DAY

(
        &self,
        months: i32,
        days: i32,
        microseconds: i64,
    )

    /// MySQL supports the DAY_MICROSECOND unit type (format is DAYS HOURS:MINUTES:SECONDS.MICROSECONDS), but it is not supported by sqlparser
    /// so we calculate the best single interval to represent the provided duration
    fn interval_to_mysql_expr(
        &self,
        months: i32,
        days: i32,
        microseconds: i64,
    ) -> Result<ast::Expr> {
        // MONTH only
        if months != 0 && days == 0 && microseconds == 0 {
            let interval = Interval {
                value: Box::new(ast::Expr::value(ast::Value::Number(
                    months.to_string(),
                    false,
                ))),
                leading_field: Some(ast::DateTimeField::Month),
                leading_precision: None,
                last_field: None,
                fractional_seconds_precision: None,
            };
            return Ok(ast::Expr::Interval(interval));
        } else if months != 0 {
            return not_impl_err!(
                "Unsupported Interval scalar with both Month and DayTime for IntervalStyle::MySQL"
            );
        }

        // DAY only
        if microseconds == 0 {
            let interval = Interval {
                value: Box::new(ast::Expr::value(ast::Value::Number(
                    days.to_string(),
                    false,
                ))),
                leading_field: Some(ast::DateTimeField::Day),
                leading_precision: None,
                last_field: None,
                fractional_seconds_precision: None,
            };
            return Ok(ast::Expr::Interval(interval));
        }

        // Calculate the best single interval to represent the provided days and microseconds

        let microseconds = microseconds + (days as i64 * 24 * 60 * 60 * 1_000_000);

        if microseconds % 1_000_000 != 0 {
            let interval = Interval {
                value: Box::new(ast::Expr::value(ast::Value::Number(
                    microseconds.to_string(),
                    false,
                ))),
                leading_field: Some(ast::DateTimeField::Microsecond),
                leading_precision: None,
                last_field: None,
                fractional_seconds_precision: None,
            };
            return Ok(ast::Expr::Interval(interval));
        }