LISTEN da NOTIFY suna samar da tsarin sadar da gabatarwa publish/subscribe da aka gina a cikin PostgreSQL — jeri ɗaya zai iya aika sadar a kan cirtaci, kuma sauran jeri masu saurare a wannan cirtaci sai suka karba shi nan nan. Hanya mai sauƙi ce ta turo abubuwan zamani daga ajiyar bayanai ba tare da neman sakonnin ba.
LISTEN order_created;
NOTIFY order_created, ;
LISTEN ya raka'ta zuwa cirtaci; NOTIFY ya aika shi (tare da mai abin ciki na rubutu na haske). Masu saurare sai suka sami sadarwa kwatsam — babu bukatar sakonnin.
-- a trigger that notifies whenever a row is inserted
CREATE FUNCTION notify_new_order() RETURNS trigger AS $$
BEGIN
PERFORM pg_notify('order_created', NEW.id::text); -- notify with the new id
RETURN NEW;
END;
$$ LANGUAGE plpgsql;
CREATE TRIGGER order_notify AFTER INSERT ON orders
FOR EACH ROW EXECUTE FUNCTION notify_new_order();
-- now inserting an order automatically pushes a notification to listeners
Hada NOTIFY tare da trigger yana ba ajiya damar aika abubuwan atomatik lokacin da bayanai suka canja (sabon odari, sabuntawa ta matsayi) — sabar aiki masu saurare a cirtaci sai suka aiki jiya nan.
Application code (Node, Python, etc.) opens a connection and LISTENs on a channel.
When a NOTIFY fires (e.g. from a trigger on data change), the app receives the event
and reacts — pushing to websockets, invalidating a cache, triggering a job, etc.
→ Real-time reactions to database changes WITHOUT polling the database.
✗ Notifications are NOT persisted — if no one is listening, the message is LOST
(no durability/queue guarantees like a real message broker)
✗ Payload is small (limited size); delivered only after the transaction COMMITS
→ Good for lightweight real-time signaling; for durable/reliable messaging use a
proper broker (RabbitMQ, Kafka) or a queue table.
LISTEN/NOTIFY fasaha ce ta amfani, kaɗan da aka sani a cikin PostgreSQL da ta samar da sadar da gabatarwa na ajiya, mahimmanci ne don ƙari amsa alamomi na zamani ga aikace-aikace ba tare da neman sakonnin ba.
Ainihin ƙimar ita ce bayyanar ajiya damar turuwa abubuwan zuwa sabar jeri nan nan lokacin da wani abu ya faru (sabon odari, canja matsayi) — yawanci tare da triggers don canja bayanai ya yi sadar ƙofa ta atomatik, wanda sabar aiki suke aiki zuwa (turuwa zuwa websockets, gurfana ajiyar kasua, haɓaka aiki gida).
Yan ƙimar ita ce da suke ba da hanyar yin abubuwan zamani mai kunna ba tare da rashin inganci na neman sakonnin ajiya a maimakon maimakon neman canja (tsarin gida da ke kau, da ba ta san bakin hadari) — tsarin da LISTEN/NOTIFY zai iya maye gurbin shi.
Ji tsarin gida (raka'ta LISTEN, gabatar NOTIFY, tare da triggers don sadar atomatik akan canja bayanai) da yadda aikace-aikace suke amfani da shi (saurare abubuwan don bugi abubuwan zamani) ya kamata a zama da muhimmi don gina aikace-aikace masu amsa, mai kunna alamomi gamit PostgreSQL kawai.
Watakila muhimmi ne sanin ƙungiyoyi: sadar ba sa gina a ajiya (rasa in babu mai saurare — babu tabbataccen takarar aiwatarwa), sannu jaƙari, da kuma kuma yi aiki bayan likita — saboda haka ya dace ga sauda mai sauki da zamani, ba maye gurbin wani cibiyar sadar mai takarar (RabbitMQ, Kafka) lokacin da ƙarfin da adanawa suka muhimmi.
Tunda abubuwan zamani masu kunna fasaha ke bukatar kuma LISTEN/NOTIFY ya bayar da hanya ta gida, ba sakonnin ba don samar da shi ne wajen sauƙi, ji shi — tsarin sadar da gabatarwa, tsarin trigger, da muhimmin shi ƙungiyoyi (lokacin da ya isa da wajen da brokar na gaske ya bukata) — ya kamata a zama da mahimmanci, tsarin da amfani PostgreSQL ilimi don gina aikace-aikace mai kunna alamomi, fasaha mai tamawayi da aka bari.