.. _library_avro:

avro

The avro library implements predicates for reading (parsing) and writing (generating) data in the Apache Avro binary format:

• https://avro.apache.org/docs/current/specification/ This library requires a backend supporting unbounded integer arithmetic.

API documentation

Open the `../../apis/library_index.html#avro <../../apis/library_index.html#avro>`__ link in a web browser.

Loading

To load all entities in this library, load the loader.lgt file:

::

| ?- logtalk_load(avro(loader)).

Testing

To test this library predicates, load the tester.lgt file:

::

| ?- logtalk_load(avro(tester)).

Schema representation

Schema files use the .avsc extension and their contents are always valid JSON values. They can be parsed using the json(curly,dash,atom) library object.

Data representation

Data to be serialized to Avro binary format files can be represented in the JSON Lines format (using the .jsonl extension) and parsed using the json_lines(curly, dash, atom) library object.

Schema Examples

Primitive type schemas:

• null
• boolean
• int
• long
• float
• double
• bytes
• string Array schema example represented as a JSON term:

  ::

  {type-array, items-int}

Encoding

Encoding is accomplished using the generate/3 or generate/4 predicates. For example, assuming the schema is just int:

::

| ?- avro::generate(bytes(Bytes), int, 42). Bytes = [84] yes

Or an array of int:

::

| ?- avro::generate(bytes(Bytes), {type-array,items-int}, [42,37,13,17]). Bytes = [8,84,74,26,34,0] yes

To include the schema in the output (as an Avro Object Container File), use the generate/4 predicate with the second argument set to true. For example:

::

| ?- avro::generate(file('output.avro'), true, {type-array,items-int}, [42,37,13,17]). yes

Decoding

Decoding is accomplished using the parse/2 or parse/3 predicates.

When parsing a file that includes a schema (Avro Object Container File), use parse/2 which returns a Schema-Data pair. For example:

::

| ?- avro::parse(file('input.avro'), Schema-Data).

When the schema is not present in the file, Schema is unified with false.

When parsing with a known schema, use instead the parse/3 predicate. For example:

::

| ?- avro::parse(bytes([84]), int, Data). Data = 42 yes