Method get_as_join_column

datafusion/expr/src/expr.rs:2035–2044

Returns the inner `Column` if any. This is a specialized version of [`Self::try_as_col`] that take Cast expressions into account when the expression is as on condition for joins. Called this method when you are sure that the expression is a `Column` or a `Cast` expression that wraps a `Column`.

(&self)

    /// Called this method when you are sure that the expression is a `Column`
    /// or a `Cast` expression that wraps a `Column`.
    pub fn get_as_join_column(&self) -> Option<&Column> {
        match self {
            Expr::Column(c) => Some(c),
            Expr::Cast(Cast { expr, .. }) => match &**expr {
                Expr::Column(c) => Some(c),
                _ => None,
            },
            _ => None,
        }
    }

    /// Return all references to columns in this expression.
    ///