A schema is a collection of logical structures of data, or schema objects. Schema objects can be created and manipulated with SQL and include the following types of objects:
One of the key concepts in streaming SQL, a stream is a continually updating data object, with columns of data similar to a database table. A stream is a schema object that is relation a but which does not store data, as a finite relation such as a table in a database does. Instead, a stream implements a publish-subscribe protocol. It can be written to by multiple writers and read from by multiple readers. Sometimes referred to as a named stream to distinguish it from an “anonymous” stream - the results of executing a streaming query.
For more detail, see the topic CREATE STREAM in this guide.
A schema object that is a stream defined in the context of a schema and associated with a server, which itself is an instance of a foreign data wrapper to provide access within SQLstream s-Server to a flow of data either from or to an external system. For example, the Extensible Common Data Adapter supports the creation of a foreign stream that will take rows (from a local stream) and send them to a Kafka topic, network feed, file, Amazon Kinesis stream, and so on.
For more detail, see the topic CREATE FOREIGN STREAM in this guide.
A schema object that records the metadata necessary for SQLstream s-Server to be able to access a table (or similar data structure) in a remote database. A Foreign Table can be used in SQL (both queries and updates) just like a local table.
For more detail, see the topic CREATE FOREIGN TABLE in this guide.
A schema object that is a relation (a structure like a table) that provides a reusable definition of a query. SQLstream s-Server supports views based on both streaming and non-streaming (finite) SELECT statements.
For more detail, see the topic CREATE VIEW in this guide..
A pump is a schema object (an extension of the SQL standard) that provides a continuously running INSERT INTO stream SELECT… FROM query functionality, thereby enabling the results of a query to be continuously entered into a named stream.
For more detail, see the topic CREATE PUMP in this guide.
SQLstream s-Server supports users in defining several types of routines: user-defined functions, user-defined procedures, and user-defined transforms.
A UDF is a user-defined routine that returns a scalar value. SQLstream s-Server allows the creation of Java or SQL functions.
For more detail, see:
A type of user-defined routine that accepts zero or more parameters but does not return a value.
For more detail, see:
Other types of objects are also stored in the SQLstream s-Server s-Server and can be created and manipulated with SQL but they are not contained in a schema; these are described in the topic Catalog Objects.