PostgreSQL (HP) (v2)

PostgreSQL integration summary

This version (v2) of Stitch’s PostgreSQL integration optimizes replication by utilizing Avro schemas to write and validate data, thereby reducing the amount of time spent on data extraction and preparation. Compared to previous versions of the PostgreSQL integration, this version boasts increased performance and overall reduced replication time.

Notable improvements and changes in this version also include:

• Expanded data type support. This version supports additional PostgreSQL data types. Refer to the PostgreSQL data types documentation for more info.
• Improved handling of JSON, JSONB, and HSTORE data types. In previous versions, these data types were treated as strings. This version will send them to your destination as JSON objects, which may result in de-nesting.
• Improved handling of schema changes in tables using Log-based Incremental Replication. Adding and removing columns in these tables will no longer cause extraction errors. Note: This limitation still applies to version 1.

Note: The following features aren’t fully supported, but are being worked on:

• Arrays of DECIMAL, NUMERIC, and TIMESTAMP(TZ) data types
• Support for some flavors of PostgreSQL. We’re in the process of testing this version of our integration with other flavors of PostgreSQL, including Amazon Aurora and Amazon RDS.

To get a look at how this version compares to the previous version of PostgreSQL, refer to the PostgreSQL version comparison documentation.

PostgreSQL feature snapshot

A high-level look at Stitch's PostgreSQL (v2) integration, including release status, useful links, and the features supported in Stitch.

Connecting PostgreSQL

PostgreSQL setup requirements

To set up PostgreSQL in Stitch, you need:

• The CREATEROLE or SUPERUSER privilege. Either privilege is required to create a database user for Stitch.

• If using Log-based Replication, you’ll need:

  • A database running PostgreSQL 9.4 or greater Earlier versions of PostgreSQL do not include logical replication functionality, which is required for Log-based Replication.
  • The SUPERUSER privilege. If using logical replication, this is required to define the appropriate server settings.
  • To connect to the master instance. Log-based replication will only work on master instances due to a feature gap in PostgreSQL 10. Based on their forums, PostgreSQL is working on adding support for using logical replication on a read replica to a future version.

  • To check for TOASTed tables and columns. TOASTed tables and columns in your PostgreSQL database can cause the following issues when using Log-Based Replication:

    1. Recurring no known snapshot errors, or
    2. Inaccurate data replication.

    Refer to the PostgreSQL documentation for more information on what TOAST is and how to identify TOASTed tables and columns in your database.

• If you’re not using Log-based Replication, you’ll need:

  • A database running PostgreSQL 9.3.x or greater. PostgreSQL 9.3.x is the minimum version Stitch supports for PostgreSQL integrations.
  • To verify if the database is a read replica, or follower. While we always recommend connecting a replica over a production database, this also means you may need to verify some of its settings - specifically the max_standby_streaming_delay and max_standby_archive_delay settings - before connecting it to Stitch. We recommend setting these parameters to 8-12 hours for an initial replication job, and then decreasing them afterwards.

Step 1: Configure database connection settings

In this step, you’ll configure the database server to allow traffic from Stitch to access it. There are two ways to connect your database:

• A direct connection will work if your database is publicly accessible.
• An SSH tunnel is required if your database isn’t publicly accessible. This method uses a publicly accessible instance, or an SSH server, to act as an intermediary between Stitch and your database. The SSH server will forward traffic from Stitch through an encrypted tunnel to the private database.

Click the option you’re using below and follow the instructions.

Step 2: Create a Stitch database user

Next, you’ll create a dedicated database user for Stitch. This will ensure Stitch is visible in any logs or audits, and allow you to maintain your privilege hierarchy.

• Instructions
• Privileges list

Step 3: Configure Log-based Incremental Replication

While Log-based Incremental Replication is the most accurate and efficient method of replication, using this replication method may, at times, require manual intervention or impact the source database’s performance. Refer to the Log-based Incremental Replication documentation for more info.

You can also use one of Stitch’s other Replication Methods, which don’t require any database configuration. Replication Methods can be changed at any time.

In this section:

• Step 3.1: Install the wal2json plugin

• Step 3.2: Edit the client authentication file

• Step 3.3: Edit the database configuration file

• Step 3.4: Restart the PostgreSQL service

• Step 3.5: Create a replication slot

Step 3.1: Install the wal2json plugin

To use Log-based Replication for your PostgreSQL integration, you must install the wal2json plugin. The wal2json plugin outputs JSON objects for logical decoding, which Stitch then uses to perform Log-based Replication.

Steps for installing the plugin vary depending on your operating system. Instructions for each operating system type are in the wal2json’s GitHub repository:

• Unix-based operating systems
• Windows

After you’ve installed the plugin, you can move onto the next step.

Step 3.2: Edit the client authentication file

Usually named pg_hba.conf, this file controls how clients authenticate to the PostgreSQL database. To ensure Stitch can read the output from the wal2json plugin, you’ll need to add replication connection rules to this file. These rules translate to “Allow the Stitch user from this IP address to perform replication on all the databases it has access to.”

This step uses the Stitch IP addresses for your data pipeline region.

1. Log into your PostgreSQL server as a superuser.
2. Locate the pg_hba.conf file, usually stored in the database cluster’s data directory. You can also locate this file by checking the value of the hba_file server parameter.

3. For each Stitch IP address, add the following line to pg_hba.conf.

   Replace the following:

   • <stitch_username> with the name of the Stitch database user
   • <stitch_ip_address> with one of the Stitch IP addresses for your data pipeline region

   host replication <stitch_username> <stitch_ip_address> md5
   

   A rule for each IP addresses for your Stitch data pipeline region must be added to pg_hba.conf. As Stitch can use any one of these IP addresses to connect during the extraction process, each of them must have their own replication connection rule.

Step 3.3: Edit the database configuration file

• Instructions
• Server settings list

wal_level=logical
max_replication_slots=5
max_wal_senders=5

Step 3.4: Restart the PostgreSQL service

After you’ve finished editing the pg_hba.conf file and configuring the database settings, restart your PostgreSQL service to ensure the changes take effect.

Step 3.5: Create a replication slot

Next, you’ll create a dedicated logical replication slot for Stitch. In PostgreSQL, a logical replication slot represents a stream of database changes that can then be replayed to a client in the order they were made on the original server. Each slot streams a sequence of changes from a single database.

Note: Replication slots are specific to a given database in a cluster. If you want to connect multiple databases - whether in one integration or several - you’ll need to create a replication slot for each database.

1. Log into the master database as a superuser.
2. Using wal2json, create a logical replication slot:

   • If you’re connecting multiple databases, you’ll need to run this command for every database you want to connect, replacing <raw_database_name> with the name of the database:

     SELECT *
     FROM pg_create_logical_replication_slot('stitch_<raw_database_name>', 'wal2json');
     

     This will create a replication slot named stitch_<raw_database_name>.

   • If you’re connecting a single database, run the following command:

     SELECT *
     FROM pg_create_logical_replication_slot('stitch', 'wal2json');
     

     This will create a replication slot named stitch.

3. Log in as the Stitch user and verify you can read from the replication slot, replacing <replication_slot_name> with the name of the replication slot:

   SELECT COUNT(*)
   FROM pg_logical_slot_peek_changes('<replication_slot_name>', null, null);
   

   If connecting multiple databases, you should verify that the Stitch user can read from each of the replication slots you created.

Note: wal2json is required to use Log-based replication in Stitch for PostgreSQL-backed databases.

Step 4: Connect Stitch

In this step, you’ll complete the setup by entering the database’s connection details and defining replication settings in Stitch.

• Step 4.1: Define the database connection details

• Step 4.2: Define the SSH connection details

• Step 4.3: Define the SSL connection details

• Step 4.4: Define the Log-based Replication setting

• Step 4.5: Create a replication schedule

• Step 4.6: Save the integration

Step 4.1: Define the database connection details

1. If you aren’t signed into your Stitch account, sign in now.

2. On the Stitch Dashboard page, click the Add Integration button.

3. Locate and click the PostgreSQL icon.

4. Fill in the fields as follows:

   • Integration Name: Enter a name for the integration. This is the name that will display on the Stitch Dashboard for the integration; it’ll also be used to create the schema in your destination.

     For example, the name “Stitch PostgreSQL” would create a schema called stitch_postgresql in the destination. Note: The schema name cannot be changed after the integration is saved.

   • Host (Endpoint): Enter the host address (endpoint) used by the PostgreSQL instance. For example: This could be a network address such as 192.68.0.1, or a server endpoint like dbname.hosting-provider.com.

   • Port: Enter the port used by the PostgreSQL instance. The default is 5432.

   • Username: Enter the Stitch PostgreSQL database user’s username.

   • Password: Enter the password for the Stitch PostgreSQL database user.

   • **: Enter the name of the PostgreSQL database you want to connect to Stitch. Stitch will ‘find’ all databases you give the Stitch user access to - a default database is only used to complete the connection. This is required for PostgreSQL integrations.

   • Include PostgreSQL schema names in destination tables: Checking this setting will include schema names from the source database in the destination table name - for example: <source_schema_name>__<table_name>.

     Stitch loads all selected replicated tables to a single schema, preserving only the table name. If two tables canonicalize to the same name - even if they’re in different source databases or schemas - name collision errors can arise. Checking this setting can prevent these issues.

     Note: This setting can not be changed after the integration is saved. Additionally, this setting may create table names that exceed your destination’s limits. For more info, refer to the Database Integration Table Name Collisions guide.

Step 4.2: Define the SSH connection details

If you’re using an SSH tunnel to connect your PostgreSQL database to Stitch, you’ll also need to define the SSH settings. Refer to the Setting up an SSH Tunnel for a database connection guide for assistance with completing these fields.

1. Click the SSH Tunnel checkbox.

2. Fill in the fields as follows:

   • SSH Host: Enter the public IP address or hostname of the server Stitch will SSH into.

   • SSH Port: Enter the SSH port on your server. (22 by default)

   • SSH User: Enter the Stitch Linux (SSH) user’s username.

Step 4.3: Define the SSL connection details

Click the Connect using SSL checkbox if you’re using an SSL connection. Note: The database must support and allow SSL connections for this setting to work correctly.

Step 4.4: Define the Log-based Replication setting

In the Log-based Replication section, you can set this as the integration’s default Replication Method.

When enabled, tables that are set to replicate will use Log-based Incremental Replication by default. If you don’t want a table to use Log-based Incremental Replication, you can change it in the Table Settings page for that table.

If this setting isn’t enabled, you’ll have to select a Replication Method for each table you set to replicate.

Step 4.5: Create a replication schedule

In the Replication Frequency section, you’ll create the integration’s replication schedule. An integration’s replication schedule determines how often Stitch runs a replication job, and the time that job begins.

PostgreSQL integrations support the following replication scheduling methods:

• Replication Frequency

• Anchor Scheduling

• Advanced Scheduling using Cron (Advanced or Premium plans only)

To keep your row usage low, consider setting the integration to replicate less frequently. See the Understanding and Reducing Your Row Usage guide for tips on reducing your usage.

Step 4.6: Save the integration

When finished, click Check and Save.

Stitch will perform a connection test to the PostgreSQL database; if successful, a Success! message will display at the top of the screen. Note: This test may take a few minutes to complete.

Step 5: Select data to replicate

The last step is to select the tables and columns you want to replicate.

Note: If a replication job is currently in progress, new selections won’t be used until the next job starts.

• Selection options
• Individual tables and columns
• All tables and columns
• Database views

Initial and historical replication jobs

After you finish setting up PostgreSQL, its Sync Status may 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 replication job for the integration. This may take some time to complete.

Free historical data loads

The first seven days of replication, beginning when data is first replicated, are free. Rows replicated from the new integration during this time won’t count towards your quota. Stitch offers this as a way of testing new integrations, measuring usage, and ensuring historical data volumes don’t quickly consume your quota.

PostgreSQL replication

In this section:

• Details about Extraction, including object and data type discovery and selecting data for replication

Extraction

For every table set to replicate, Stitch will perform the following during Extraction:

• Discover table schemas and type discovered columns

• Select records for replication

Discovery

During Discovery, Stitch will:

• Determine table schemas

• Type the data in discovered columns

Determining table schemas

During this phase of Discovery, Stitch queries system tables to retrieve metadata about the objects the Stitch database user has access to. This metadata is used to determine which databases, tables, and columns to display in Stitch for replication.

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 typing

Refer to the PostgreSQL data types documentation for more info about how PostgreSQL data is typed for selected columns.

Data replication

During data replication, Stitch will query the selected tables and columns using the Replication Method defined for the table:

• Full Table

• Key-based Incremental

• Log-based Incremental

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