How do I take a postgres data backup on Hasura

Option 1:

Exec a pg_dump command on your Postgres container:

pg_dump -U username -d dbname > data.sql

In practice, you probably only want the data and not the hasura metadata or schema_migration information. This is a better 'data export' type command: 

pg_dump -U username -d dbname --data-only --schema public > data.sql

Option 2:

If Postgres is running as a Docker container:

# Exec into the postgres container
$ docker exec -ti <postgres-id> -- /bin/bash
# Run pg_dump
root@postgres-3391217220-t7bbc:/$ pg_dump -U postgres -d postgres --data-only --schema public > db.sql
^D

# Back on your local machine, copy the dump
$ docker cp <postgres-id>:/db.sql db.sql

Hasura has a pgdump API command, enabled by default. Here are the docs: https://docs.hasura.io/1.0/graphql/manual/api-reference/pgdump.html

What the docs currently lack is an example. Here's an example I use to dump the Hasura data, but not the schema (which comes from migrations) in order to import it into my locally hosted dev hasura (insert your own hasura-admin-secret, assuming you use one, or replace with other headers as needed):

HASURA_SECRET=som3_Secr3t_Her3
curl -d '{"-Fc", "opts": ["--data-only"]}' -H "x-hasura-admin-secret: $HASURA_SECRET" https://your-host-url.com/v1alpha1/pg_dump > dumpfile

2022: Hasura v.2.1.1

To export data from a postgres/Hasura instance, we need to use Postman or a curl client to make a http POST request against a hidden Hasura endpoint /v1alpha1/pg_dump like so:

http://<your-hasura-host>/v1alpha1/pg_dump

An example curl command:

curl -d '{"opts": ["-a", "-O", "-x", "--inserts", "--exclude-schema=hdb_catalog"], "clean_output": true, "source": "default"}' -H "x-hasura-admin-secret:your-admin-secret-here" http://your-hasura-host/v1alpha1/pg_dump

The above adds a header to specify your Hasura admin secret:

x-hasura-admin-secret:<your admin secret key>

And the -d adds a JSON body with options ("opts") for pg_dump & Hasura's endpoint handler:

{
  "opts": ["-a", "-O", "-x", "--inserts", "--exclude-schema=hdb_catalog"],
  "clean_output": true,
  "source": "default"
}

The pg_dump options ("opts") above are:

  • -a: data-only, not schemas
  • -O: no ownership statements
  • -x: no access privilege statements
  • --inserts: use SQL statements, not psql commands
  • --exclude-schema=hdb_catalog: no Hasura migration/metadata related records, just our data

The clean_output key/value removes a bunch of SET statements & comments from the dump output such as:

--
-- PostgreSQL database dump
--

-- Dumped from database version 12.4 (Debian 12.4-1.pgdg100+1)
-- Dumped by pg_dump version 13.4 (Debian 13.4-4.pgdg100+1)

SET statement_timeout = 0;
SET lock_timeout = 0;
SET idle_in_transaction_session_timeout = 0;
SET client_encoding = 'UTF8';
SET standard_conforming_strings = on;
SELECT pg_catalog.set_config('search_path', '', false);
SET check_function_bodies = false;
SET xmloption = content;
SET client_min_messages = warning;
SET row_security = off;

source specifies the name of the database to dump. Usually this would be default unless you changed it when setting up Hasura.

The output you get should be a single SET statement followed by a bunch of INSERT INTO statements.

This can be copy/pasted directly into Hasura Console's Data > SQL tab and run to import the dumped data.

References/Useful Links

  • https://www.postgresql.org/docs/13/app-pgdump.html
  • https://hasura.io/docs/latest/graphql/core/api-reference/pgdump.html
  • https://hasura.io/docs/latest/graphql/core/migrations/advanced/seed-data-migration.html

Notes

I needed the pg_dump as seed data to use when applying a Hasura migration, from an old instance to a new Hasura instance. But (in my case) the initial migration output by Hasura CLI on the old instance included a bunch of hdb_catalog create schema statements, which would ensure failure when applying the migration onto a new Hasura instance. (The hdb_catalog schema/tables already exist on a new/fresh Hasura install)

To correct this, I needed to reset migrations on the old instance and redo the migration commands (as shown in the aforementioned link). This new migration output didn't include the hdb_catalog schema, and could be applied OK to the new Hasura instance.

I could then just run the pg_dump output in Hasura Console SQL tab/window on the new instance to repopulate my tables.

Tags:

Postgresql

Pg Dump

Hasura

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