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supabase/apps/reference/docs/guides/database/replication.mdx
2022-08-13 22:24:54 +08:00

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---
id: replication
title: 'Replication'
slug: replication
---
import Tabs from '@theme/Tabs'
import TabItem from '@theme/TabItem'
Replication is a technique for copying the data from one database to another. Supabase uses replication functionality to provide a real-time API. Replication is useful for:
- Spreading out the "load." For example, if your database has a lot of reads, you might want to split it between two databases.
- Reducing latency. For example, you may want one database in London to serve your European customers, and one in New York to serve the US.
Replication is done through _publications_, a method of choosing which changes to send to other systems (usually another Postgres database). Publications can be managed in the [Dashboard](https://app.supabase.com) or with SQL.
## Manage publications in the Dashboard
1. Go to the [Database](https://app.supabase.com/project/_/database/tables) page in the Dashboard.
2. Click on **Replication** in the sidebar.
3. Control which database events are sent by toggling **Insert**, **Update**, and **Delete**.
4. Control which tables broadcast changes by selecting **Source** and toggling each table.
<video width="99%" muted playsInline controls="true">
<source
src="/docs/videos/api/api-realtime.mp4"
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## Create a publication
This publication contains changes to all tables.
```sql
create publication publication_name
for all tables;
```
## Create a publication to listen to individual tables
```sql
create publication publication_name
for table table_one, table_two;
```
## Add tables to an existing publication
```sql
alter publication publication_name
add table table_name;
```
## Listen to `insert`
```sql
create publication publication_name
for all tables
with (publish = 'insert');
```
## Listen to `update`
```sql
create publication publication_name
for all tables
with (publish = 'update');
```
## Listen to `delete`
```sql
create publication publication_name
for all tables
with (publish = 'delete');
```
## Remove a publication
```sql
drop publication if exists publication_name;
```
## Recreate a publication
If you're recreating a publication, it's best to do it in a transaction to ensure the operation succeeds.
```sql
begin;
-- remove the realtime publication
drop publication if exists publication_name;
-- re-create the publication but don't enable it for any tables
create publication publication_name;
commit;
```