Struct lance_file::v2::reader::ReaderProjection

pub struct ReaderProjection {
    pub schema: Arc<Schema>,
    pub column_indices: Vec<u32>,
}

Selecting columns from a lance file requires specifying both the index of the column and the data type of the column

Partly, this is because it is not strictly required that columns be read into the same type. For example, a string column may be read as a string, large_string or string_view type.

A read will only succeed if the decoder for a column is capable of decoding into the requested type.

Note that this should generally be limited to different in-memory representations of the same semantic type. An encoding could theoretically support “casting” (e.g. int to string, etc.) but there is little advantage in doing so here.

Fields

schema: Arc<Schema>

The data types (schema) of the selected columns. The names of the schema are arbitrary and ignored.

column_indices: Vec<u32>

The indices of the columns to load. Note, these are the indices of the top level fields only

Trait Implementations

impl Clone for ReaderProjection

fn clone(&self) -> ReaderProjection

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for ReaderProjection

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.