Function projection_names 

pub fn projection_names(
    schema: &SchemaRef,
    projection: &[ColumnId],
) -> Result<Vec<String>, LookupError>

Resolve projection column indices to their names in schema, in projection order. An empty projection means “all columns” and returns every name in schema order. Shared by the lookup backends to turn the query projection into a column selection.

Errors

Returns LookupError::Internal if a projection index is out of range.