Database change events

With change capture on, every write to a chosen table publishes an event on the channel db.table.<table>. Use it to refresh a list when data changes, without polling.

#Turn it on

1. 1

   Realtime › Database change data capture

   Switch it on and pick the tables. Nothing is published for tables you didn't pick.

2. 2

   Allow listeners

   Add a rule that lets the right callers SUBSCRIBE to db.table.<table> (Policy language (SPL)).

3. 3

   Listen

   Subscribe like any channel.

   JavaScript

   sovaria.realtime.channel('db.table.orders', {
     onMessage: async (event) => {
       // { event_type: 'row.inserted' | 'row.updated' | 'row.deleted', table, schema, timestamp, event_id, row_count }
       setOrders(await loadMyOrders())   // re-read through your rules
     },
   })

#What an event contains

Events say that rows changed, not their contents. Clients then read what they may see through your access policies and row-level security, so a listener never receives rows it couldn't query itself.

#Delivery and ordering

• Events are written to a durable outbox before the write returns and delivered from there with retries, so a restart delays them rather than losing them.
• Events for one table arrive in commit order.
• A retried delivery carries the same event_id; duplicates are dropped by realtime, and your code can ignore any it has already handled.
• The same events can also call your HTTPS endpoint — database webhooks (Database webhooks).

#An event didn't arrive