Struct FilterCandidate 

pub(crate) struct FilterCandidate {
    expr: Arc<dyn PhysicalExpr>,
    required_bytes: usize,
    can_use_index: bool,
    projection: Vec<usize>,
    schema_mapper: Arc<dyn SchemaMapper>,
    filter_schema: SchemaRef,
}

A candidate expression for creating a RowFilter.

Each candidate contains the expression as well as data to estimate the cost of evaluating the resulting expression.

See the module level documentation for more information.

Fields

expr: Arc<dyn PhysicalExpr>

required_bytes: usize

Estimate for the total number of bytes that will need to be processed to evaluate this filter. This is used to estimate the cost of evaluating the filter and to order the filters when reorder_predicates is true. This is generated by summing the compressed size of all columns that the filter references.

can_use_index: bool

Can this filter use an index (e.g. a page index) to prune rows?

projection: Vec<usize>

The projection to read from the file schema to get the columns required to pass through a SchemaMapper to the table schema upon which we then evaluate the filter expression.

schema_mapper: Arc<dyn SchemaMapper>

A SchemaMapper used to map batches read from the file schema to the filter’s projection of the table schema.

filter_schema: SchemaRef

The projected table schema that this filter references