Supabase Edge Functions

Supabase has native integration for event sourcing. This uses a combination of a Postgres triggers and Supabase Edge Functions.

Triggers can be setup to run on various events within the database, such as inserting, updating and deleting rows in a database. Supabase makes it easy to call a server-side edge function from a trigger.

Setting up triggers with Edge Functions

First, you need to ensure that the pg_net extension is enabled for the "public" schema of your project - this is an extension that enables you to call an Edge Function url via SQL. The steps are as follows:

1. in the Supabase Platform dashboard go to "Database" -> "Extensions", search for pg_net, and ensure it is toggled on
2. create an Edge Function, following the instructions in the Supabase documentation
3. configure a trigger to call the Edge Function, following the instructions here

Example

The example below uses an AFTER INSERT trigger, which will be called whenever a new row in my_table is created (both directly and when a new row created in the client is synced to the server).

The trigger then uses the pg_net extension to call an Edge Function by URL. The Edge Function is passed a JSON body with the id of the new row inserted. It then uses this to retrieve the row using the Supabase Client API and process it.

-- Drop any previous version of the trigger and function
DROP TRIGGER IF EXISTS "my_edge_function_trigger" ON "public"."my_table";
DROP FUNCTION IF EXISTS call_my_edge_function_trigger();

-- The function called by the trigger
CREATE FUNCTION call_my_edge_function_trigger() RETURNS trigger AS $$
BEGIN
  PERFORM net.http_post(
    'https://YOUR-SUPABASE-HOST.supabase.co/functions/v1/my_edge_function',
    ('{"id": "' || new.id || '"}')::jsonb,
    '{}'::jsonb,
    '{"Content-type":"application/json","Authorization":"YOUR-SERVICE-ROLL-KEY"}'::jsonb
  );
  RETURN NULL;
END;
$$ LANGUAGE plpgsql;

-- Configure the function to be called by an "AFTER INSERT" trigger
CREATE TRIGGER "my_edge_function_trigger" AFTER INSERT
ON "public"."my_table" FOR EACH ROW
EXECUTE FUNCTION call_my_edge_function_trigger();

-- This next line is required to ensure that triggers on the table are called
-- as a result of the Electric sync
ALTER TABLE "public"."my_table" ENABLE ALWAYS TRIGGER my_edge_function_trigger;

This code can either be run directly against your Postgres via the Supabase console, or you can include it in your database migrations.

You can see an example of this pattern in our Checkout Example.