Module writer 

Core functionality for writing Arrow arrays as Avro data

Implements the primary writer interface and record encoding logic. Avro writer implementation for the arrow-avro crate.

Overview

Use this module to serialize Arrow RecordBatch values into Avro. Two output formats are supported:

• AvroWriter — writes an Object Container File (OCF): a self‑describing file with header (schema JSON + metadata), optional compression, data blocks, and sync markers. See Avro 1.11.1 “Object Container Files.” https://avro.apache.org/docs/1.11.1/specification/#object-container-files
• AvroStreamWriter — writes a Single Object Encoding (SOE) Stream (“datum” bytes) without any container framing. This is useful when the schema is known out‑of‑band (i.e., via a registry) and you want minimal overhead.

Which format should you use?

• Use OCF when you need a portable, self‑contained file. The schema travels with the data, making it easy to read elsewhere.
• Use the SOE stream when your surrounding protocol supplies schema information (i.e., a schema registry). The writer automatically adds the per‑record prefix:
  • SOE: Each record is prefixed with the 2-byte header (0xC3 0x01) followed by an 8‑byte little‑endian CRC‑64‑AVRO fingerprint, then the Avro body. See Avro 1.11.1 “Single object encoding”. https://avro.apache.org/docs/1.11.1/specification/#single-object-encoding
  • Confluent wire format: Each record is prefixed with magic byte 0x00 followed by a big‑endian 4‑byte schema ID, then the Avro body. Use FingerprintStrategy::Id(schema_id). https://docs.confluent.io/platform/current/schema-registry/fundamentals/serdes-develop/index.html#wire-format
  • Apicurio wire format: Each record is prefixed with magic byte 0x00 followed by a big‑endian 8‑byte schema ID, then the Avro body. Use FingerprintStrategy::Id64(schema_id). https://www.apicur.io/registry/docs/apicurio-registry/1.3.3.Final/getting-started/assembly-using-kafka-client-serdes.html#registry-serdes-types-avro-registry

Choosing the Avro schema

By default, the writer converts your Arrow schema to Avro (including a top‑level record name). If you already have an Avro schema JSON you want to use verbatim, put it into the Arrow schema metadata under the avro.schema key before constructing the writer. The builder will use that schema instead of generating a new one (unless strip_metadata is set to true in the options).

Compression

For OCF, you may enable a compression codec via WriterBuilder::with_compression. The chosen codec is written into the file header and used for subsequent blocks. SOE stream writing doesn’t apply container‑level compression.

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Modules

encoder 🔒

Encodes RecordBatch into the Avro binary format. Avro Encoder for Arrow types.

format

Logic for different Avro container file formats. Avro Writer Formats for Arrow.

Structs

Writer

Generic Avro writer.

WriterBuilder

Builder to configure and create a Writer.

Type Aliases

AvroStreamWriter

Alias for an Avro Single Object Encoding stream writer.

AvroWriter

Alias for an Avro Object Container File writer.