alexvanboxel commented on issue #10413: [BEAM-9035] Typed options for Row 
Schema and Field
URL: https://github.com/apache/beam/pull/10413#issuecomment-598367815
 
 
   @reuvenlax 
   
   > copying schema's
   
   most of the use cases we have result in a transformation based on options 
they generally result on a change of the schema. But it's important to not drop 
all the meta data because in another (following) transform maybe needs that 
meta data. Examples
   
   ```protobuf
   message PaymentServiceProvider {
        PaymentPlatform payment_platform = 1 [
                (vptech.data.contract.v1.description) = "The booking platform 
payment",
                (vptech.data.contract.v1.enum_prefix) = "PAYMENT_PLATFORM_",
                (vptech.data.contract.v1.optional) = true ]
   }
   ```
   in beam the `payment_platform` is a field with a Enum logical type. It has 3 
options.
   1. transforms that handles `description`, the field now has a real Beam 
description and 2 options left
   2. transforms that handles `enum_prefix`, strips the prefix from the enum 
and changes the type from enum to string, and with one remaining option
   3. the validation transforms looks to the `optional` option. if data quality 
is not good with move the element to the deadletter otherwise, field is now 
string with no options.
   
   as you see, each transform changes the schema slightly.
   
   > FieldType can be nullable
   
   The implementation for each format (proto, avro, zeta, calcite) has control 
over setting it. It should set type nullable too `false`. 
   
   > Options are no different than schemas
   
   I disagree that they are the same. A schema describe the types of rows and 
fields, options are meta data on top of the those rows and fields. An option 
being there has a meaning, I never saw an option that was null. It's not 
possible in proto, neither in avro. 
   Proto makes it possible to describe a field extension that lives in a 
package that you can attach on any arbitrary 
field/message/enum/file/service/method (resulting on this being an option). 
Avro you can add arbitrary json on the record and field. It's not that you 
attach a strongly typed record to each field...
   
   If it's a blocker, I'll change it too move this along (but then I need to 
change the BIP-1: 
https://cwiki.apache.org/confluence/display/BEAM/%5BBIP-1%5D+Beam+Schema+Options)
   
   > should translate to a single Beam option named "my_method_option" not to 
two separate options.
   
   No, it would translate to 
`package.where.the.extension.is.defined.my_method_option`
   
   > dots are also used to represent package names of course. Is this the main 
reason you need to support dots?
   
   yes. How could I ever map the above options if options would really be a 
row? I also have an avro implementation ready. It also has don't. Here is a 
real world example:
   
   ```avro
       { "name": "ts", "type": {
               "type": "string",
               "connect.version": 1,
               "connect.default": "1970-01-01T00:00:00Z",
               "connect.name": "io.debezium.time.ZonedTimestamp"
           }
       },
   ```
   
   this results in a Beam type of `STRING` with 3 options: `connect.version`, 
`connect.version` and `connect.name`.
   
   

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