What is a Source in RisingWave?

A source in RisingWave is a connection to an external data system that streams data into the database. Learn about source types, supported connectors, and when to use a source vs. a table.

What is a source?

A source in RisingWave is a connection to an external data system that streams data into the database. Sources define where data comes from and how it should be parsed — they are the entry point for all data ingestion in RisingWave.

When you create a source with CREATE SOURCE, RisingWave establishes a connection to the external system and begins reading data according to the specified format and encoding. Sources do not persist data inside RisingWave — they provide a live window into the external data stream.

How sources work

-- Create a source that reads from a Kafka topic
CREATE SOURCE pageviews (
  user_id INT,
  page_url VARCHAR,
  view_time TIMESTAMP
) WITH (
  connector = 'kafka',
  topic = 'pageviews',
  properties.bootstrap.server = 'broker:9092'
) FORMAT PLAIN ENCODE JSON;

Once created, a source can be:

• Queried directly (for supported connectors like Kafka, S3, Iceberg) — useful for ad-hoc exploration and validation.
• Referenced in materialized views — to build continuous streaming pipelines.
• Used as input for sinks — to transform and deliver data to downstream systems.

Source vs. Table

A common question is when to use a source versus a table with connector settings. The key difference is data persistence:

	Source	Table (with connector)
Persists data in RisingWave	No	Yes
Supports DML (INSERT, UPDATE, DELETE)	No	Yes
Required for CDC connectors	No — must use Table	Yes
Primary key required	No	Required for CDC
Best for	Exploration, stateless pipelines	Persistent storage, CDC, updates

Rule of thumb: Use a source when you only need to stream data through to materialized views or sinks without storing the raw data. Use a table when you need to persist the raw data, use CDC connectors, or need to update/delete individual rows.

Supported source connectors

RisingWave supports a wide range of source connectors:

Message brokers: Apache Kafka, Apache Pulsar, Amazon Kinesis, MQTT, NATS, Google Pub/Sub

Databases (CDC): PostgreSQL, MySQL, SQL Server, MongoDB — via native CDC connectors, no Kafka or Debezium required

Object storage: Amazon S3, Google Cloud Storage, Azure Blob Storage

Data lakes: Apache Iceberg

Other: Webhooks, Datagen (for testing)

For the full list, see Supported source connectors.

Data formats and encoding

Sources support multiple data formats:

• JSON — most common; schema inferred or specified in DDL
• Avro — requires schema registry URL (Kafka sources)
• Protobuf — requires schema specification
• CSV — for file-based sources
• Bytes — raw bytes for custom parsing
• Debezium JSON — for CDC events from Kafka topics

-- Avro source with schema registry
CREATE SOURCE events WITH (
  connector = 'kafka',
  topic = 'events',
  properties.bootstrap.server = 'broker:9092'
) FORMAT PLAIN ENCODE AVRO (
  schema.registry = 'http://schema-registry:8081'
);

Related topics

• CREATE SOURCE — SQL reference
• Ingestion overview — Connector list and ingestion patterns
• Source, Table, MV, and Sink — Core object comparison
• CDC with RisingWave — Native CDC connectors