fc-common: add PostgreSQL LISTEN/NOTIFY infrastructure

Signed-off-by: NotAShelf <raf@notashelf.dev>
Change-Id: Iffdb2fa758825e8c5d5791bf4fb15c8e6a6a6964

crates/common/migrations/015_listen_notify_triggers.sql

@@ -0,0 +1,61 @@
+-- PostgreSQL LISTEN/NOTIFY triggers for event-driven reactivity
+-- Emits notifications on builds/jobsets mutations so daemons can wake immediately
+
+-- Trigger function: notify on builds changes
+CREATE OR REPLACE FUNCTION notify_builds_changed() RETURNS trigger AS $$
+BEGIN
+    PERFORM pg_notify('fc_builds_changed', json_build_object(
+        'op', TG_OP,
+        'table', TG_TABLE_NAME
+    )::text);
+    RETURN NULL;
+END;
+$$ LANGUAGE plpgsql;
+
+-- Trigger function: notify on jobsets changes
+CREATE OR REPLACE FUNCTION notify_jobsets_changed() RETURNS trigger AS $$
+BEGIN
+    PERFORM pg_notify('fc_jobsets_changed', json_build_object(
+        'op', TG_OP,
+        'table', TG_TABLE_NAME
+    )::text);
+    RETURN NULL;
+END;
+$$ LANGUAGE plpgsql;
+
+-- Builds: new build inserted (queue-runner should wake)
+CREATE TRIGGER trg_builds_insert_notify
+    AFTER INSERT ON builds
+    FOR EACH ROW
+    EXECUTE FUNCTION notify_builds_changed();
+
+-- Builds: status changed (queue-runner should re-check, e.g. deps resolved)
+CREATE TRIGGER trg_builds_status_notify
+    AFTER UPDATE ON builds
+    FOR EACH ROW
+    WHEN (OLD.status IS DISTINCT FROM NEW.status)
+    EXECUTE FUNCTION notify_builds_changed();
+
+-- Jobsets: new jobset created (evaluator should wake)
+CREATE TRIGGER trg_jobsets_insert_notify
+    AFTER INSERT ON jobsets
+    FOR EACH ROW
+    EXECUTE FUNCTION notify_jobsets_changed();
+
+-- Jobsets: relevant fields changed (evaluator should re-check)
+CREATE TRIGGER trg_jobsets_update_notify
+    AFTER UPDATE ON jobsets
+    FOR EACH ROW
+    WHEN (
+        OLD.enabled IS DISTINCT FROM NEW.enabled
+        OR OLD.state IS DISTINCT FROM NEW.state
+        OR OLD.nix_expression IS DISTINCT FROM NEW.nix_expression
+        OR OLD.check_interval IS DISTINCT FROM NEW.check_interval
+    )
+    EXECUTE FUNCTION notify_jobsets_changed();
+
+-- Jobsets: deleted (evaluator should wake to stop tracking)
+CREATE TRIGGER trg_jobsets_delete_notify
+    AFTER DELETE ON jobsets
+    FOR EACH ROW
+    EXECUTE FUNCTION notify_jobsets_changed();