Avro Schema: Build Avro Schema from Schema Fields

Question

I am trying to write a function to calculate a diff between two avro schemas and generate another schema.

schema_one = {
  "type": "record",
  "name": "schema_one",
  "namespace": "test",
  "fields": [
    {
      "name": "type",
      "type": "string"
    },
    {
      "name": "id",
      "type": "string"
    }
  ]
}

schema_two = {
  "type": "record",
  "name": "schema_two",
  "namespace": "test",
  "fields": [
    {
      "name": "type",
      "type": "string"
    }
  ]
}

To get elements field in schema_one not in schema_two

import org.apache.avro.Schema._
import org.apache.avro.{Schema, SchemaBuilder}
val diff: Set[Schema.Field] =  schema_one.getFields.asScala.toSet.filterNot(schema_two.getFields.asScala.toSet)

So far, so good.

I want to build a new schema from diff and I expect it to be:

schema_three = {
  "type": "record",
  "name": "schema_three",
  "namespace": "test",
  "fields": [
    {
      "name": "id",
      "type": "string"
    }
  ]
}

I cant seem to find any method within Avro SchemaBuilder to achieve this without having to explicitly provide named fields. i.e build Schema given Schema.Fields

For example:

SchemaBuilder.record("schema_three").namespace("test").fromFields(diff)

Is there a way to achieve this? Appreciate comments.

Answer 1

I was able to achieve this using the kite sdk "org.kitesdk" % "kite-data-core" % "1.1.0"

  val schema_namespace = schema_one.getNamespace
  val schema_name = schema_one.getName

  val schemas = diff.map( f => {
    SchemaBuilder
      .record(schema_name)
      .namespace(schema_namespace)
      .fields()
      .name(f.name())
      .`type`(f.schema())
      .noDefault()
        .endRecord()
   }
  )

  val schema_three = SchemaUtil.merge(schemas.asJava)