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115 lines
3.3 KiB
Plaintext
115 lines
3.3 KiB
Plaintext
---
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id: postgres-changes
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title: Postgres Changes
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description: Getting started with Realtime's Postgres Changes feature
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---
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Supabase Postgres Changes listen for database changes and sends them to clients. Clients are required to subscribe with a JWT dictating which changes they are allowed to receive based on the database's [Row Level Security](/docs/guides/auth/row-level-security).
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:::caution
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Anyone with access to a valid JWT signed with the project's JWT secret is able to listen to your database's changes, unless tables have [Row Level Security](/docs/guides/auth/row-level-security) enabled and policies in place.
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:::
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Clients can choose to receive `INSERT`, `UPDATE`, `DELETE`, or `*` (all) changes for all changes in a schema, a table in a schema, or a column's value in a table.Your clients can only listen to tables in the `public` schema and you must first enable the tables you want your clients to listen to. You can do this in the [Replication](https://app.supabase.com/project/_/database/replication) section in the Dashboard or with the [SQL editor](https://app.supabase.com/project/_/sql):
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```sql
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begin;
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-- remove the supabase_realtime publication
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drop publication if exists supabase_realtime;
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-- re-create the supabase_realtime publication with no tables
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create publication supabase_realtime;
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commit;
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-- add a table to the publication
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alter publication supabase_realtime add table messages;
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```
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By default, only `new` record changes are sent but if you want to receive the `old` record (previous values) whenever you `UPDATE` or `DELETE` a record,
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you can set the `replica identity` of your table to `full`:
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```sql
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alter table messages replica identity full;
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```
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To listen to all changes in the `public` schema:
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```js
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const { createClient } = require('@supabase/supabase-js')
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const supabase = createClient(
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process.env.SUPABASE_URL,
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process.env.SUPABASE_KEY
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)
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/*
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Channel name can be any string.
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Event name can can be one of:
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- INSERT
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- UPDATE
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- DELETE
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- *
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*/
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const channel = supabase
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.channel('schema-db-changes')
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.on('postgres_changes', { event: '*', schema: 'public' }, (payload) =>
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console.log(payload)
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)
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.subscribe()
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```
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To listen to changes on a table in the `public` schema:
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```js
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// Supabase client setup
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const channel = supabase
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.channel('table-db-changes')
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.on(
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'postgres_changes',
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{ event: 'INSERT', schema: 'public', table: 'messages' },
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(payload) => console.log(payload)
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)
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.subscribe()
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```
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To listen to changes when a column's value in a table matches a client-specified value:
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```js
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// Supabase client setup
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const channel = supabase
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.channel('value-db-changes')
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.on(
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'postgres_changes',
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{
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event: 'UPDATE',
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schema: 'public',
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table: 'messages',
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filter: 'body=eq.hey',
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},
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(payload) => console.log(payload)
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)
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.subscribe()
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```
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To listen to different events and schema/tables/filters combinations with the same channel:
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```js
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// Supabase client setup
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const channel = supabase
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.channel('db-changes')
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.on(
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'postgres_changes',
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{ event: '*', schema: 'public', table: 'messages', filter: 'body=eq.bye' },
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(payload) => console.log(payload)
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)
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.on(
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'postgres_changes',
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{ event: 'INSERT', schema: 'public', table: 'users' },
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(payload) => console.log(payload)
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)
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.subscribe()
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```
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