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How to load data from PostgreSQL to PostgreSQL

01. Access Data

  • 01. Access Data
  • 02. Transform and Prepare PostgreSQL data
  • 03. Load Data
  • 04. Update Data
  • 05. Extract Data

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This post will help you to load your data stored in PostgreSQL to PostgreSQL. By doing this you will be able to perform advanced analysis on a system that is dedicated for analytics and is suitable for this kind of data payloads, like PostgreSQL, without worrying about interfering with the production setup.

Generally speaking, replicating a PostgreSQL to any other database system is not a trivial task. Exporting a PostgreSQL database into CSV files using the pg_dump command and loading them into any other system is not enough. You also need to take care of the loading of new or updated data using a cron job that will constantly trigger the execution of a script that will check for new updates in your tables. However, especially in cases where latency is an important factor, this process can be extremely slow. In addition, depending on the selected destination, the data loading process can be significantly different.

Alternatively, you can simplify the process of syncing data from PostgreSQL to PostgreSQL by using RudderStack, which does all the heavy lifting in just a few clicks so that you can focus on what matters, the exploration and the analysis of your company’s data.

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Access your data on PostgreSQL

The first step in migrating your PostgreSQL data to any kind of data warehouse solution is to access your data and start extracting it.

There are many ways of doing this, like, for example, a logical replication log as previously mentioned. In this case, you need to listen to the log for changes on the database and reflect them on the target system. When pulling data from a database you also need to be able to filter tables, columns, find a way to identify updates, and replicate the appropriate database schema considering also that it will end up in a columnar database for analytics.

Another way is by using a JDBC importer. In this case, any input configuration will contain all the appropriate values for the database authentication and connection. By appropriately configuring the JDBC importer you can control each table’s behavior during import and altering its schema as well if desired. Moreover, pagination of data importing can be simulated by querying tables in batching mode.

About PostgreSQL data

No matter the product of your company, the chances are that the most valuable data, this capturing your customers’ interaction with your company will be held in your production PostgreSQL database.

From the users’ interaction with your platform or e-shop to product descriptions and user-generated events, this data needs to be further analyzed in order to identify what aspects of the product you need to focus on next, what are the most commonly faced problems, and how you can possibly get extra traction and more users. Most certainly you will also want to enrich this data with other coming from your ticketing system, your accounting software or your marketing platform.

Having all the data stored in a database dedicated to performing analytics, you can:

  1. Generate ongoing reports by calculating the key performance indicators that matter the most to you
  2. Develop and test predictive applications aiming to automate the company’s core business tasks
  3. Connect with the business intelligence tool of your choice and create interactive dashboards to communicate better the insights you have derived across all teams.

Transform and prepare your PostgreSQL data

After you have accessed your data on PostgreSQL, you will have to transform it based on two main factors,

  1. The limitations of the database that the data will be loaded onto
  2. The type of analysis that you plan to perform

Each system has specific limitations on the data types and data structures that it supports. Also, you have to choose the right data types. Again, depending on the system that you will send the data to, you will have to make the right choices.

While for the most common data types the mapping choices may seem to be obvious, each database system will most probably support a set of more “sophisticated” and database-specific types whose mapping choices requires careful consideration since they can limit the expressivity of your queries and restrict your analysts on what they can do directly out of the database.

However, plan to push the data to another PostgreSQL database. You probably don’t have to worry about the data types, unless you have some reasons related to the analysis that you will perform.

Each table is a collection of columns with a predefined data type like an integer or VARCHAR. PostgreSQL, like any other SQL database supports a wide range of different data types.

A typical strategy for loading data from PostgreSQL to a Postgres database is to create a schema where you will map each API endpoint to a table. Each key inside the PostgreSQL API endpoint response should be mapped to a column of that table, and you should ensure the right conversion to a Postgres compatible data type.

Load data from PostgreSQL to PostgreSQL

For example, if an endpoint from PostgreSQL returns a value as String, you should convert it into a VARCHAR with a predefined max size or TEXT data type. Tables can then be created on your database using the CREATE SQL statement.

Once you have defined your schema and created your tables with the proper data types, you can start loading data into your database.

The preferred way of adding larger datasets into a PostgreSQL database is by using the COPY command. COPY is copying data from a file on a file system accessible by the Postgres instance, in this way much larger datasets can be inserted into the database in less time. COPY requires physical access to a file system to load data.

Nowadays, with cloud-based, fully managed databases, getting direct access to a file system is not always possible. If this is the case and you cannot use a COPY statement, then another option is to use PREPARE together with INSERT to end up with optimized and more performant INSERT queries.

Updating your PostgreSQL data on PostgreSQL

As you will be generating more data on PostgreSQL, you will need to update your older data on PostgreSQL. This includes new records together with updates to older records that, for any reason, have been updated on PostgreSQL.

You will need to periodically check PostgreSQL for new data and repeat the previously described process while updating your currently available data if needed. Updating an already existing row on a PostgreSQL table is achieved by creating UPDATE statements.

Another issue that you need to take care of is the identification and removal of any duplicate records on your database. Either because PostgreSQL does not have a mechanism to identify new and updated records or because of errors on your data pipelines, duplicate records might be introduced to your database.

In general, ensuring the quality of the data that is inserted in your database is a big and difficult issue, and PostgreSQL features like TRANSACTIONS can help tremendously. However, they do not solve the problem in the general case.

The best way to load data from PostgreSQL to PostgreSQL

So far, we just scraped the surface of what can be done with PostgreSQL and how to load data into it. The way to proceed relies heavily on the data you want to load, from which service they are coming from, and the requirements of your use case. Things can get even more complicated if you want to integrate data coming from different sources.

A possible alternative, instead of writing, hosting, and maintaining a flexible data infrastructure, is to use a product like RudderStack that can handle this kind of problem automatically for you.

RudderStack integrates with multiple sources or services like databases, CRM, email campaigns, analytics, and more. Quickly and safely move all your data from PostgreSQL to PostgreSQL and start generating insights from your data.

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Test out our event stream, ELT, and reverse-ETL pipelines. Use our HTTP source to send data in less than 5 minutes, or install one of our 12 SDKs in your website or app.

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