By default, the driver automatically infers a relational schema by inspecting the Avro data. This section describes the connection properties available to configure these dynamic schemas.

Detecting Columns

The columns identified during the discovery process depend on the FlattenArrays and FlattenObjects properties. If FlattenObjects is set (this is the default), nested objects will be flattened into a series of columns.

Example Data Set

To provide an example of how these options work, consider the following schema:

{
  "type" : "record",
  "name" : "Root",
  "fields" : [ {
    "name" : "id",
    "type" : [ "null", "long" ]
  }, {
    "name" : "name",
    "type" : [ "null", "string" ]
  }, {
    "name" : "annual_revenue",
    "type" : [ "null", "long" ]
  }, {
    "name" : "offices",
    "type" : {
      "type" : "array",
      "items" : "string"
    }
  }, {
    "name" : "address",
    "type" : [ "null", {
      "type" : "record",
      "name" : "Address",
      "namespace" : "root",
      "fields" : [ {
        "name" : "city",
        "type" : [ "null", "string" ]
      }, {
        "name" : "state",
        "type" : [ "null", "string" ]
      }, {
        "name" : "street",
        "type" : [ "null", "string" ]
      } ]
    } ]
  }]
}

Also consider the following example data for the above schema:

{
  "id": 12,
  "name": "Lohia Manufacturers Inc.",
  "annual_revenue": 35600000,
  "offices": [
    "Chapel Hill",
    "London",
    "New York"
  ],
  "address": {
    "city": "Chapel Hill",
    "state": "NC",
    "street": "Main Street"
  }
}

Using FlattenObjects

If FlattenObjects is set, all nested objects will be flattened into a series of columns. The above example will be represented by the following columns:

Column Name	Data Type	Example Value
id	Integer	12
name	String	Lohia Manufacturers Inc.
address.street	String	Main Street
address.city	String	Chapel Hill
address.state	String	NC
offices	String	["Chapel Hill", "London", "New York"]
annual_revenue	Double	35,600,000

If FlattenObjects is not set, then the address.street, address.city, and address.state columns will not be broken apart. The address column of type string will instead represent the entire object. Its value would be the following:

    {street: "Main Street", city: "Chapel Hill", state: "NC"}
  

Using FlattenArrays

The FlattenArrays property can be used to flatten array values into columns of their own. This is only recommended for arrays that are expected to be short, for example the coordinates below:

"coord": [ -73.856077, 40.848447 ]

The FlattenArrays property can be set to 2 to represent the array above as follows:

Column Name	Data Type	Example Value
coord.0	Float	-73.856077
coord.1	Float	40.848447