anchor.diff:  
   and private ManyColumnGenerator
       ( builder
  -    , column
  +    , column : Column option
       , element : ElementBlueprint
  -    , elementId : Column
       , conversion : ConversionMethod
       ) =
  -    inherit EntityReaderColumnGenerator(builder, column)
  +    inherit EntityReaderColumnGenerator(builder)
  +    let elementId =
  +        match element.Shape with
  +        | Composite { Identity = Some id } -> id
  +        | _ -> failwith "Unsupported collection type"
       let elemTy = element.Output
       let staticTemplate = typedefof<_ StaticEntityReaderTemplate>.MakeGenericType(elemTy)
       let entTemplate = typedefof<_ EntityReaderTemplate>.MakeGenericType(elemTy)
  
positive.code:         | One { Shape = Composite composite } ->
              StaticEntityReaderTemplate.ImplementReader(builder, composite, readerBuilder)
          | Many (element, conversion) ->
              ()
          builder.CreateType()
  
  and private StaticEntityReaderTemplate<'ent>() =
  
negative.code:     abstract member DefinePush : unit -> Op<'x, 'x S>
  
  type private PrimitiveColumnGenerator(builder, column, primitive : Primitive) =
      inherit EntityReaderColumnGenerator(builder)
      let output = column.Blueprint.Value.Output
      let mutable colValue = null
      let mutable colInfo = null
  