message: remove fast_field_cardinality from FastValue
  unused and at the wrong placed
diff: @@ -32,7 +32,7 @@ pub use self::readers::FastFieldReaders;
  pub(crate) use self::readers::{type_and_cardinality, FastType};
  pub use self::serializer::{Column, CompositeFastFieldSerializer};
  pub use self::writer::{FastFieldsWriter, IntFastFieldWriter};
  -use crate::schema::{Cardinality, FieldType, Type, Value};
  +use crate::schema::{Type, Value};
  use crate::{DateTime, DocId};
  mod alive_bitset;
  @@ -58,12 +58,6 @@ pub trait MultiValueLength {
  pub trait FastValue:
  MonotonicallyMappableToU64 + Copy + Send + Sync + PartialOrd + 'static
  {
  - /// Returns the fast field cardinality that can be extracted from the given
  - /// `FieldType`.
  - ///
  - /// If the type is not a fast field, `None` is returned.
  - fn fast_field_cardinality(field_type: &FieldType) -> Option<Cardinality>;
  -
  /// Returns the `schema::Type` for this FastValue.
  fn to_type() -> Type;
  @@ -75,53 +69,24 @@ pub trait FastValue:
  }
  impl FastValue for u64 {
  - fn fast_field_cardinality(field_type: &FieldType) -> Option<Cardinality> {
  - match *field_type {
  - FieldType::U64(ref integer_options) => integer_options.get_fastfield_cardinality(),
  - FieldType::Facet(_) => Some(Cardinality::MultiValues),
  - _ => None,
  - }
  - }
  -
  fn to_type() -> Type {
  Type::U64
  }
  }
  impl FastValue for i64 {
  - fn fast_field_cardinality(field_type: &FieldType) -> Option<Cardinality> {
  - match *field_type {
  - FieldType::I64(ref integer_options) => integer_options.get_fastfield_cardinality(),
  - _ => None,
  - }
  - }
  -
  fn to_type() -> Type {
  Type::I64
  }
  }
  impl FastValue for f64 {
  - fn fast_field_cardinality(field_type: &FieldType) -> Option<Cardinality> {
  - match *field_type {
  - FieldType::F64(ref integer_options) => integer_options.get_fastfield_cardinality(),
  - _ => None,
  - }
  - }
  -
  fn to_type() -> Type {
  Type::F64
  }
  }
  impl FastValue for bool {
  - fn fast_field_cardinality(field_type: &FieldType) -> Option<Cardinality> {
  - match *field_type {
  - FieldType::Bool(ref integer_options) => integer_options.get_fastfield_cardinality(),
  - _ => None,
  - }
  - }
  -
  fn to_type() -> Type {
  Type::Bool
  }
  @@ -139,16 +104,6 @@ impl MonotonicallyMappableToU64 for DateTime {
  }
  impl FastValue for DateTime {
  - /// Converts a timestamp microseconds into DateTime.
  - ///
  - /// **Note the timestamps is expected to be in microseconds.**
  - fn fast_field_cardinality(field_type: &FieldType) -> Option<Cardinality> {
  - match *field_type {
  - FieldType::Date(ref options) => options.get_fastfield_cardinality(),
  - _ => None,
  - }
  - }
  -
  fn to_type() -> Type {
  Type::Date
  }
  @@ -209,7 +164,7 @@ mod tests {
  use super::*;
  use crate::directory::{CompositeFile, Directory, RamDirectory, WritePtr};
  use crate::merge_policy::NoMergePolicy;
  - use crate::schema::{Document, Field, Schema, SchemaBuilder, FAST, STRING, TEXT};
  + use crate::schema::{Cardinality, Document, Field, Schema, SchemaBuilder, FAST, STRING, TEXT};
  use crate::time::OffsetDateTime;
  use crate::{DateOptions, DatePrecision, Index, SegmentId, SegmentReader};
  