How to define avro schema for complex json document?

Question

I have a JSON document that I would like to convert to Avro and need a schema to be specified for that purpose. Here is the JSON document for which I would like to define the avro schema:

{
 "uid": 29153333,
 "somefield": "somevalue",
 "options": [
   {
     "item1_lvl2": "a",
     "item2_lvl2": [
       {
         "item1_lvl3": "x1",
         "item2_lvl3": "y1"
       },
       {
         "item1_lvl3": "x2",
         "item2_lvl3": "y2"
       }
     ]
   }
 ]
}

I'm able to define the schema for the non-complex types but not for the complex "options" field:

{
  "namespace" : "my.com.ns",
  "type" :  "record",
  "fields" : [
     {"name": "uid", "type": "int"},
     {"name": "somefield", "type": "string"}
     {"name": "options", "type": .....}
  ]
}

Thanks for the help!

Scan

Answer 1

You need to use Avro complex types, specifically arrays and records. And then nest these together:

{
  "namespace" : "my.com.ns",
  "name": "myrecord",
  "type" :  "record",
  "fields" : [
     {"name": "uid", "type": "int"},
     {"name": "somefield", "type": "string"},
     {"name": "options", "type": {
        "type": "array",
        "items": {
            "type": "record",
            "name": "lvl2_record",
            "fields": [
                {"name": "item1_lvl2", "type": "string"},
                {"name": "item2_lvl2", "type": {
                    "type": "array",
                    "items": {
                        "type": "record",
                        "name": "lvl3_record",
                        "fields": [
                            {"name": "item1_lvl3", "type": "string"},
                            {"name": "item2_lvl3", "type": "string"}
                        ]
                    }
                }}
            ]
        }
     }}
  ]
}

Also, to improve readiblity, you can split the schema into multiple files.

Bautista

> in correct order On one level of nesting, Avro doesn't care about field ordering. The fields are accessed by name during deserialization, based on the schema the reader knows. – Nympho

By "in correct order" I meant in corresponding hierarchical order. I removed that misleading phrase. – Bautista

Record and enum names: upper CamelCase please. – Rolo

Answer 2

This online tool (http://avro4s-ui.landoop.com/) is very practical, you can generate the AVRO schema by a given valid json.

Enidenigma

This is fantastic. I had a rather complex JSON format I needed an avro schema for to convert into parquet, and this tool did the trick. – Prebo