1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64

use super::*;

/// Create a Column Expression based on a column name.
///
/// # Arguments
///
/// * `name` - A string slice that holds the name of the column. If a column with this name does not exist when the
///   LazyFrame is collected, an error is returned.
///
/// # Examples
///
/// ```ignore
/// // select a column name
/// col("foo")
/// ```
///
/// ```ignore
/// // select all columns by using a wildcard
/// col("*")
/// ```
///
/// ```ignore
/// // select specific column by writing a regular expression that starts with `^` and ends with `$`
/// // only if regex features is activated
/// col("^foo.*$")
/// ```
pub fn col(name: &str) -> Expr {
    match name {
        "*" => Expr::Wildcard,
        _ => Expr::Column(ColumnName::from(name)),
    }
}

/// Selects all columns. Shorthand for `col("*")`.
pub fn all() -> Expr {
    Expr::Wildcard
}

/// Select multiple columns by name.
pub fn cols<I: IntoVec<String>>(names: I) -> Expr {
    let names = names.into_vec();
    let names = names
        .into_iter()
        .map(|v| ColumnName::from(v.as_str()))
        .collect();
    Expr::Columns(names)
}

/// Select multiple columns by dtype.
pub fn dtype_col(dtype: &DataType) -> Expr {
    Expr::DtypeColumn(vec![dtype.clone()])
}

/// Select multiple columns by dtype.
pub fn dtype_cols<DT: AsRef<[DataType]>>(dtype: DT) -> Expr {
    let dtypes = dtype.as_ref().to_vec();
    Expr::DtypeColumn(dtypes)
}

/// Select multiple columns by index.
pub fn index_cols<N: AsRef<[i64]>>(indices: N) -> Expr {
    let indices = indices.as_ref().to_vec();
    Expr::IndexColumn(Arc::from(indices))
}