Question 46 - DSA-C02 discussion

What is an External Function?

An external function calls code that is executed outside Snowflake.

The remotely executed code is known as a remote service.

Information sent to a remote service is usually relayed through a proxy service.

Snowflake stores security-related external function information in an API integration.

External Function:

An external function is a type of UDF. Unlike other UDFs, an external function does not contain its own code; instead, the external function calls code that is stored and executed outside Snowflake.

Inside Snowflake, the external function is stored as a database object that contains information that Snowflake uses to call the remote service. This stored information includes the URL of the proxy service that relays information to and from the remote service.

Remote Service:

The remotely executed code is known as a remote service.

The remote service must act like a function. For example, it must return a value.

Snowflake supports scalar external functions; the remote service must return exactly one row for each row received.

Proxy Service:

Snowflake does not call a remote service directly. Instead, Snowflake calls a proxy service, which relays the data to the remote service.

The proxy service can increase security by authenticating requests to the remote service.

The proxy service can support subscription-based billing for a remote service. For example, the proxy service can verify that a caller to the remote service is a paid subscriber.

The proxy service also relays the response from the remote service back to Snowflake.

Examples of proxy services include:

Amazon API Gateway.

Microsoft Azure API Management service.

API Integration:

An integration is a Snowflake object that provides an interface between Snowflake and third-party services. An API integration stores information, such as security information, that is needed to work with a proxy service or remote service.

An API integration is created with the CREATE API INTEGRATION command.

Users can write and call their own remote services, or call remote services written by third parties. These remote services can be written using any HTTP server stack, including cloud serverless compute services such as AWS Lambda.