Avro Format

Format: Serialization Schema Format: Deserialization Schema

The Apache Avro format allows to read and write Avro data based on an Avro schema. Currently, the Avro schema is derived from table schema.

Dependencies

In order to setup the Avro format, the following table provides dependency information for both projects using a build automation tool (such as Maven or SBT) and SQL Client with SQL JAR bundles.

You can download flink-sql-avro from Download

<dependency>
  <groupId>org.apache.flink</groupId>
  <artifactId>flink-avro</artifactId>
  <version>1.12-SNAPSHOT</version>
</dependency>

How to create a table with Avro format

Here is an example to create a table using Kafka connector and Avro format.

CREATE TABLE user_behavior (
  user_id BIGINT,
  item_id BIGINT,
  category_id BIGINT,
  behavior STRING,
  ts TIMESTAMP(3)
) WITH (
 'connector' = 'kafka',
 'topic' = 'user_behavior',
 'properties.bootstrap.servers' = 'localhost:9092',
 'properties.group.id' = 'testGroup',
 'format' = 'avro'
)

Format Options

Option Required Default Type Description
format
required (none) String Specify what format to use, here should be 'avro'.
avro.codec
optional (none) String For Filesystem only, the compression codec for avro. No compression as default. The valid enumerations are: deflate, snappy, bzip2, xz.

Data Type Mapping

Currently, the Avro schema is always derived from table schema. Explicitly defining an Avro schema is not supported yet. So the following table lists the type mapping from Flink type to Avro type.

Flink SQL type Avro type Avro logical type
CHAR / VARCHAR / STRING string
BOOLEAN boolean
BINARY / VARBINARY bytes
DECIMAL fixed decimal
TINYINT int
SMALLINT int
INT int
BIGINT long
FLOAT float
DOUBLE double
DATE int date
TIME int time-millis
TIMESTAMP long timestamp-millis
ARRAY array
MAP
(key must be string/char/varchar type)
map
MULTISET
(element must be string/char/varchar type)
map
ROW record

In addition to the types listed above, Flink supports reading/writing nullable types. Flink maps nullable types to Avro union(something, null), where something is the Avro type converted from Flink type.

You can refer to Avro Specification for more information about Avro types.