Enum SelectItemSource 

pub enum SelectItemSource {
    BaseColumn(usize),
    WindowFunction(String),
    Expression(Expression),
    ExpressionWithWindow(Expression, Vec<String>),
}

Source of a SELECT item value

Variants

BaseColumn(usize)

WindowFunction(String)

Window function name - stored in lowercase for O(1) lookup in window_value_map

Expression(Expression)

ExpressionWithWindow(Expression, Vec<String>)

Expression containing one or more window functions. Stores (expression, list_of_window_function_names_lowercase). Each Window node in the expression is replaced with a placeholder identifier referencing the corresponding name at the same index.