Function col_refs

prqlc/prqlc/src/sql/pq/preprocess.rs:532–537

(exprs: Vec<&Expr>)

}

fn col_refs(exprs: Vec<&Expr>) -> Vec<CId> {
    exprs
        .into_iter()
        .flat_map(|expr| expr.kind.as_column_ref().cloned())
        .collect()
}

/// Pull Compute transforms in front of other transforms if possible.
/// Position of Compute is important for two reasons: