Method simplify

datafusion/functions/src/string/concat.rs:293–299

Simplify the `concat` function by 1. filtering out all `null` literals 2. concatenating contiguous literal arguments For example: `concat(col(a), 'hello ', 'world', col(b), null)` will be optimized to `concat(col(a), 'hello world', col(b))`

(
        &self,
        args: Vec<Expr>,
        _info: &SimplifyContext,
    )

    /// will be optimized to
    /// `concat(col(a), 'hello world', col(b))`
    fn simplify(
        &self,
        args: Vec<Expr>,
        _info: &SimplifyContext,
    ) -> Result<ExprSimplifyResult> {
        simplify_concat(args)
    }

    fn documentation(&self) -> Option<&Documentation> {
        self.doc()