Stream Statements

SQL Data Definition Language (DDL) statements create and manage data streams.

CREATE STREAM

The CREATE STREAM statement registers a new stream connected to an external source:

CREATE STREAM stream_name
    ( column_name <data_type> [ DEFAULT <constant_value> ] [ ,...n ] )
    WITH ( property_name = expression [, ...] );

For detailed property definitions and stream options, refer to the Stream Overview Guide.

Default Column Values

Define default values for columns in stream schemas. If an incoming event omits the field or contains null, rekuiper assigns the declared default value:

CREATE STREAM sensor_stream (
    device_id string,
    temperature float DEFAULT 25.0,
    status string DEFAULT "normal"
) WITH (
    DATASOURCE = "sensor/telemetry",
    FORMAT = "json"
);

Example

CREATE STREAM my_stream ()
WITH (
    DATASOURCE = "topic/temperature",
    FORMAT = "json",
    KEY = "id",
    BUFFER_FULL_POLICY = "block"
);

Buffer Policy

Use the BUFFER_FULL_POLICY property to control ingestion when the input buffer is full.

• block: The source pauses reading until the buffer has available space.
• dropOldest: The source deletes the oldest record to accept the incoming record. Default if omitted.

The server rejects other values with an error during stream creation and update.

Multi-Stream Rules (Joins)

When a rule query joins multiple streams (e.g. FROM stream1 JOIN stream2 ON ...), all streams referenced in the query must configure an identical BUFFER_FULL_POLICY. If one stream uses block while another uses dropOldest, the server rejects the rule with a validation error to prevent asymmetric backpressure deadlocks and erratic tuple drops.

DESCRIBE STREAM

The DESCRIBE STREAM statement returns the schema and configuration of a registered stream:

DESCRIBE STREAM stream_name;

DROP STREAM

The DROP STREAM statement removes a registered stream definition:

DROP STREAM stream_name;

CAUTION

Delete all rules that reference the stream before running DROP STREAM.

SHOW STREAMS

The SHOW STREAMS statement lists all streams currently registered in the database:

SHOW STREAMS;