Add database upgrade file 08

etc/db/upgrades/upgrade08-81d9ea19→74b3de5c.sql

@@ -0,0 +1,75 @@
+-- Upgrade the database from commit 81d9ea19 to 74b3de5c.
+--
+-- This upgrade affects the `public` schema only.
+--
+-- It creates a new table, `queue_items`, for storing
+-- requests and responses related to inter-API communication.
+-- At the moment this means Equinor's ASAQC API, but it
+-- should be applicable to others as well if the need
+-- arises.
+--
+-- As well as the table, it adds:
+--
+-- * `queue_item_status`, an ENUM type.
+-- * `update_timestamp`, a trigger function.
+-- * Two triggers on `queue_items`.
+--
+-- To apply, run as the dougal user:
+--
+-- psql < $THIS_FILE
+--
+-- NOTE: It will fail harmlessly if applied twice.
+
+
+-- Queues are global, not per project,
+-- so they go in the `public` schema.
+
+
+CREATE TYPE queue_item_status
+AS ENUM (
+	'queued',
+	'cancelled',
+	'failed',
+	'sent'
+);
+
+CREATE TABLE IF NOT EXISTS queue_items (
+	item_id serial NOT NULL PRIMARY KEY,
+	-- One day we may want multiple queues, in that case we will
+	-- have a queue_id and a relation of queue definitions.
+	-- But not right now.
+	-- queue_id integer NOT NULL REFERENCES queues (queue_id),
+	status queue_item_status NOT NULL DEFAULT 'queued',
+	payload jsonb NOT NULL,
+	results jsonb NOT NULL DEFAULT '{}'::jsonb,
+	created_on timestamptz NOT NULL DEFAULT current_timestamp,
+	updated_on timestamptz NOT NULL DEFAULT current_timestamp,
+	not_before timestamptz NOT NULL DEFAULT '1970-01-01T00:00:00Z',
+	parent_id integer NULL REFERENCES queue_items (item_id)
+);
+
+-- Sets `updated_on` to current_timestamp unless an explicit
+-- timestamp is part of the update.
+--
+-- This function can be reused with any table that has (or could have)
+-- an `updated_on` column of time timestamptz.
+CREATE OR REPLACE FUNCTION update_timestamp () RETURNS trigger AS
+$$
+	BEGIN
+		IF NEW.updated_on IS NOT NULL THEN
+			NEW.updated_on := current_timestamp;
+		END IF;
+		RETURN NEW;
+	EXCEPTION
+		WHEN undefined_column THEN RETURN NEW;
+	END;
+$$
+LANGUAGE plpgsql;
+
+CREATE TRIGGER queue_items_tg0
+BEFORE INSERT OR UPDATE ON public.queue_items
+FOR EACH ROW EXECUTE FUNCTION public.update_timestamp();
+
+CREATE TRIGGER queue_items_tg1
+AFTER INSERT OR DELETE OR UPDATE ON public.queue_items
+FOR EACH ROW EXECUTE FUNCTION public.notify('queue_items');