PostgreSQL

Connecting PostgreSQL

In this article, we’ll walk you through connecting your PostgreSQL database to Stitch. You’ll need some tech expertise to complete the setup, so we recommend looping in a developer or a member of your tech team to help out if you haven’t done this before.

Connecting a PostgreSQL database is a seven-step process:

1. Whitelist the Stitch IP addresses
2. Retrieve the Stitch Public Key *
3. Create a Stitch Linux user *
4. Create a database user for Stitch
5. Enter the connection info into Stitch
6. Define the Replication Frequency
7. Sync data & select Replication Methods

* These steps are only required if you’re using an SSH tunnel to connect the database to Stitch.

Whitelist Stitch’s IP Addresses

For the connection to be successful, you’ll need to configure your firewall to allow access from our IP addresses. Whitelist the following IPs before continuing onto the next step:

• 52.23.137.21/32

• 52.204.223.208/32

• 52.204.228.32/32

• 52.204.230.227/32

Retrieve Your Public Key

If you aren’t using an SSH tunnel to connect, you can skip this step.

The Public Key is used to authorize the Stitch Linux user. If the key isn’t properly installed, Stitch will be unable to access your database.

To retrieve the key:

1. On the Stitch Dashboard page, click the Add an Integration button.
2. Click the PostgreSQL icon.
3. When the credentials page displays, click the Encryption Type menu and select the SSH Tunnel option.
4. The Public Key will display, along with the other SSH fields.

Create a Stitch Linux User

If you aren’t using an SSH tunnel to connect, you can skip this step.

Note that anything inside square brackets - [like this] - is something you need to define when running the commands yourself.

To create the new user, run the following commands as root on your Linux server:

adduser [stitch username] -p
mkdir /home/[stitch username]
mkdir /home/[stitch username]/.ssh

To ensure the user has access to the database, we need to import the Public Key into authorized_keys. Copy the entire key into the authorized_keys file as follows:

touch /home/[stitch username]/.ssh/authorized_keys
"< [PASTE KEY HERE] >" >> /home/[stitch username]/.ssh/authorized_keys

To finish creating the user, alter the permissions on the /home/[stitch username] directory to allow access via SSH:

chown -R [stitch username]:[stitch username] /home/[stitch username]
chmod -R 700 /home/[stitch username]/.ssh

In the next step, you’ll create a database user for Stitch.

Create a Stitch Database User

Your organization may require a different process, but the simplest way to create this user is to execute the following query when logged into the PostgreSQL database as a user with the right to grant privileges. This user should also own the schema that Stitch is being granted access to.

CREATE USER [stitch username] WITH ENCRYPTED PASSWORD '[secure password]';
GRANT CONNECT ON DATABASE [database name] TO [stitch username];
GRANT USAGE ON SCHEMA [schema name] TO [stitch username];
GRANT SELECT ON ALL TABLES IN SCHEMA [schema name] TO [stitch username];
ALTER DEFAULT PRIVILEGES IN SCHEMA [schema name] GRANT SELECT ON TABLES TO [stitch username];

Replace [secure password here] with a secure password, which can be different than the SSH password. Additionally, make sure you replace [database name] and [schema name] with the appropriate names in your database.

If you want to connect multiple databases or schemas, repeat this process as necessary.

Enter the Connection Info into Stitch

To wrap things up, you need to enter the database connection and user info into Stitch.

1. On the Stitch Dashboard page, click the Add an Integration button.

2. Click the PostgreSQL icon.

3. Enter a name for the integration. This is the name that will display on the for the integration; it’ll also be used to create the schema in your data warehouse.

   For example, the name “Stitch PostgreSQL” would create a schema called stitch_postgres in the data warehouse. This schema is where all the tables for this integration will be stored.

4. Fill in the connection info for the database:
   • Host: In general, this will be 127.0.0.1 (localhost), but could also be some other network address (ex: 192.68.0.1) or your server’s public IP address. Note that this must be the actual address - entering localhost into this field will cause connection issues.
   • Port: Enter the PostgreSQL port on your server. (5432 by default)
   • Username: Enter the Stitch PostgreSQL user’s username.
   • Password: Enter the password for the Stitch PostgreSQL user.
   • Database: Enter the name of the default database Stitch will connect to. Don’t worry: we’ll find all the databases you gave the Stitch user access to, but we need an initial database to complete the connection.

If you’re using an SSH tunnel to connect your PostgreSQL database to Stitch, you’ll also need to do the following:

1. Click the Encryption Type menu and select SSH Tunnel from the dropdown.
2. Fill in the SSH connection info for the database in these fields:
   • Remote Address: Enter the IP address or hostname of the server Stitch will SSH into.
   • SSH Port: Enter the SSH port on your server. (22 by default)
   • Username: Enter the Stitch Linux (SSH) user’s username.

In addition, click the Connect using SSL checkbox if you’re using an SSL connection.

Define the Replication Frequency

The Replication Frequency controls how often Stitch will attempt to replicate data from your PostgreSQL integration. By default the frequency is set to 30 minutes, but you can change it to better suit your needs.

Before setting the Replication Frequency, note that:

• The more often PostgreSQL is set to replicate, the higher the number of replicated rows.

• The number of rows in the source may not equal the number of rows replicated by Stitch. Tables that use Full Table Replication will result in a higher number of replicated rows.

• If you’re using a data warehouses that doesn’t natively support nested structures, you’ll see a higher number of replicated rows due to the de-nesting Stitch performs.

To help prevent overages, we recommend setting the Replication Frequency to something less frequent - like 6 hours instead of 30 minutes. For tips on reducing your row count, check out the Reducing Your Row Count section of our Billing Guide.

After selecting a Replication Frequency, click Save Integration.

Select Tables & Columns to Sync

The last step is to select the tables and columns you want to sync. When you sync a table, you’ll also need to define its Replication Method and, if using Incremental Replication, its Replication Key.

You can sync tables and columns by:

1. In the Integration Details page, click the Tables to Replicate tab.
2. Locate a table you want to replicate.
3. Click the checkbox next to the object’s name. A green checkmark means the object is set to sync.
4. If there are child objects, they’ll automatically display and you’ll be prompted to select some.
5. After you set a table to sync, the Table Settings page will display.
6. In the Table Settings page, you’ll need to define the table’s Replication Method and, if using Incremental Replication, its Replication Key.
7. Repeat this process for every table you want to replicate. Note that when you sync a table, by default all columns will also be set to sync.

PostgreSQL’s Intial Sync

After you finish setting up PostgreSQL, you might see its Sync Status show as Pending on either the Stitch Dashboard or in the Integration Details page.

For a new integration, a Pending status indicates that Stitch is in the process of scheduling the initial sync for the integration. This may take some time to complete.

Replicating Data from PostgreSQL

When you connect a database as an input, Stitch only needs read-only access to the databases, tables, and columns you want to sync. There are two processes Stitch runs during the Extraction phase of the replication process: a structure sync and a data sync.

Structure Sync

The first part of the replication process is called a structure sync. This process will detect any changes to the structure of your database. For example: a new column is added to one of the tables you’re syncing in Stitch.

To perform a structure sync, Stitch runs queries on the following tables in the pg_catalog schema:

• pg_class
• pg_attribute
• pg_index
• pg_namespace

Data Sync

The second step in the Extraction phase is called a data sync. This is where Stitch actually pulls data out of your database for replication. The method Stitch uses is the same for all databases, but differs depending on the Replication Method that each table uses.

Full Table Replication

For tables using Full Table Replication, Stitch runs a single query (shown below) and reads out of the resulting cursor in batches.

select column_a, column_b <,...> from table_a

Incremental Replication

For tables using Incremental Replication, Stitch runs a single query (shown below) and reads out of the associated cursor in batches.

select column_a, column_b <,...> from table_a
where replication_key_column >=’last_bookmark_value’
order by replication_key_column

Recommendations

While we make every effort to ensure the queries that Stitch runs don’t impart significant load on your databases, we still have some recommendations for guaranteeing database performance:

• Use a replica database instead of connecting directly. We recommend using read replicas in lieu of directly connecting production databases with high availability and performance requirements.
• Apply indexes to Replication Key columns. We restrict and order our replication queries by this column, so applying an index to the columns you’re using as Replication Keys can improve performance.

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