$ cat data.avro | avro-tools getschema /dev/stdin
{
  "type" : "record",
  "name" : "test",
  "fields" : [ {
    "name" : "a",
    "type" : {
      "type" : "array",
      "items" : {
        "type" : "array",
        "items" : "string"
      }
    }
  }, {
    "name" : "b",
    "type" : {
      "type" : "long",
      "logicalType" : "timestamp-millis"
    }
  }, {
    "name" : "c",
    "type" : [ "null", "long" ]
  } ]
}
$ cat avro.data | avrocat 
{"a": [["a1", "a2"], [""]], "b": 1578539189956, "c": null}
{"a": [], "b": 1578539189956, "c": {"long": 1}}
$ cat data.avro |  clickhouse-local   --input-format Avro --structure 'a Array(Array(String)), b DateTime64(3), c Nullable(Int64)' -q 'select *  from table format Pretty'
┏━━━━━━━━━━━━━━━━━━━━┳━━━━━━━━━━━━━━━━━━━━━━━━━┳━━━━━━┓
┃ a                  ┃                       b ┃    c ┃
┡━━━━━━━━━━━━━━━━━━━━╇━━━━━━━━━━━━━━━━━━━━━━━━━╇━━━━━━┩
│ [['a1','a2'],['']] │ 2020-01-08 21:06:29.956 │ ᴺᵁᴸᴸ │
├────────────────────┼─────────────────────────┼──────┤
│ []                 │ 2020-01-08 21:06:29.956 │    1 │
└────────────────────┴─────────────────────────┴──────┘

$ clickhouse-local -q "select toNullable('str') as a, toInt64(123) as b, now64() as c  format Avro" | avro-tools getschema /dev/stdin
{
  "type" : "record",
  "name" : "row",
  "fields" : [ {
    "name" : "a",
    "type" : [ "null", "string" ]
  }, {
    "name" : "b",
    "type" : "long"
  }, {
    "name" : "c",
    "type" : {
      "type" : "long",
      "logicalType" : "timestamp-millis"
    }
  } ]
}
$ clickhouse-local -q "select toNullable('str') as a, toInt64(123) as b, now64() as c  format Avro" | avrocat
{"a": {"string": "str"}, "b": 123, "c": 1578539557810}

CREATE TABLE data (`a` String, `b` Int64, `c` Nullable(Float64)) ENGINE = Kafka() SETTINGS kafka_broker_list = 'kafka-broker:9092', kafka_topic_list = 'topic', kafka_group_name = 'group', kafka_format = 'AvroConfluent', kafka_num_consumers = 1, input_format_avro_schema_registry_url = 'http://platform-schema-registry'