Published at Feb 7, 2024
Data Lifecycle
Written by Juan José Gouvêa
In the digital era, where data accumulates at an unprecedented pace, managing this deluge of information effectively is crucial for businesses, governments, and other organizations. This is where a data retention policy (DRP) becomes essential.
A data retention policy is a set of guidelines that governs how long an organization retains its data and how it's disposed of once it's no longer needed. This policy outlines not only the duration for which the data is kept but also the manner of its storage and management during its lifecycle.
In this article, we’ll describe what makes a good retention policy in general as part of the data management lifecycle, explain its specific benefits for developers, and how you can create one in PostgreSQL. Finally, we’ll show how Timescale simplifies and automates this process. If you haven’t tried Timescale yet, you can create a free account and experiment for 30 days.
The importance of a data retention policy extends beyond mere organizational tidiness. Here are a few key reasons why a sound data retention policy is indispensable:
1. Compliance with regulations: Various industries are subject to different regulatory requirements dictating how long and in what manner data should be stored. For instance, the healthcare sector under HIPAA or financial services under GDPR have specific data retention guidelines.
2. Data management efficiency: With a clear policy, organizations can avoid the clutter of unnecessary data, thus improving the efficiency of their database systems.
3. Legal protection: In the event of legal proceedings, having a well-documented data retention policy can serve as a protective measure, ensuring that relevant data is available and that non-relevant data is not unnecessarily scrutinized.
4. Cost management: Storing data incurs costs, especially in large quantities. A DRP helps in eliminating unnecessary data storage, thus reducing expenses.
A comprehensive data retention policy serves multiple purposes, ensuring not only regulatory compliance but also efficient data management. Here’s what should ideally be included in an effective data retention policy:
1. Identification of data types: Clearly categorize data types (like personal data, transaction records, etc.) and their specific retention requirements.
2. Retention timeframes: Define exact durations for how long each type of data should be retained, in alignment with legal and business needs.
3. Access and security protocols: Outline who has access to the data, under what circumstances, and the security measures in place to protect it.
4. Procedures for data disposal: Establish guidelines for securely and permanently deleting data that's no longer required.
5. Regular policy reviews: Include provisions for periodic reviews of the policy to adapt to new legal requirements or business changes.
6. Compliance and auditing procedures: Document processes for ensuring policy compliance and conducting audits.
Data preservation and data retention, while closely related, serve distinct purposes:
Data retention: This refers to holding onto data for a specified period for operational or compliance reasons. It focuses on the utility and legal requirements of keeping the data.
Data preservation: This is more about maintaining data integrity and accessibility over a long period, often for historical or research purposes. It emphasizes protecting the data from technological obsolescence or degradation.
Data retention is a component of data preservation, but while retention is often driven by legal and business needs, preservation is driven by the value of the data over time.
The short answer is “no.” Data retention and backups are different concepts with distinct objectives:
Data retention: This is about how long data is kept before it’s deleted or archived. It’s governed by a policy that dictates an organization's data lifespan.
Data backup: Backups refer to creating copies of data so that it can be restored in the event of data loss, corruption, or a disaster. Backups are part of a disaster recovery plan and are not necessarily related to how long the data is retained.
While both are crucial for data management, data retention is focused on the data lifecycle, whereas backups are focused on data recovery and availability. A robust data management strategy integrates both aspects, ensuring not just the availability of data but also its compliant management over time.
Now that we have gotten into the basics of data retention policies for organizations, let’s see how they can help software developers work. Unsurprisingly, data retention policies offer numerous benefits to developers, particularly those who manage and manipulate large volumes of data. Understanding and implementing these policies can lead to several advantages:
1. Streamlined data management: Developers can more efficiently manage databases when they are not overloaded with outdated or irrelevant data. This efficiency can lead to faster query responses and smoother data manipulation.
2. Reduced storage costs: Developers can significantly reduce storage requirements and associated costs by regularly purging unnecessary data.
3. Improved data security: A clear data retention policy helps identify which data needs more stringent security measures, thus enhancing overall data protection.
4. Regulatory compliance: For developers working in industries with strict data regulations, adhering to data retention policies is crucial to avoid legal complications.
5. Enhanced data quality: Regularly reviewing and pruning data as per the agreed retention policies ensures that the data in use is more relevant and up-to-date, leading to better decision-making.
6. Simplified data recovery: In the event of a system failure, having less outdated data can simplify the recovery process.
Building on the foundational principles of data retention, let's explore how PostgreSQL specifically caters to these requirements.
PostgreSQL offers various strategies for implementing data retention policies:
1. Table partitioning: Partitioning tables based on criteria like date can simplify data management. For example, data can be partitioned by month or year, making it easier to drop entire partitions when their retention period expires.
CREATE TABLE sales (
record_id serial NOT NULL,
ordered_at date NOT NULL,
data jsonb
) PARTITION BY RANGE (ordered_at);
CREATE TABLE sales_2023 PARTITION OF sales
FOR VALUES FROM ('2023-01-01') TO ('2024-01-01');
2. Dropping data: PostgreSQL allows for deleting no longer needed data. This can be done manually or through automated scripts based on the retention policy, which makes things slightly more complex.
You can use the DELETE SQL command to delete data from a Postgres table. Here is the basic syntax:
DELETE FROM table_name WHERE condition;
table_name: Replace this with the name of the table from which you want to delete data.
condition: This is the condition that determines which rows to delete. Rows that satisfy the condition will be deleted.
For example, if you have a table named sales but haven’t partitioned it and want to delete orders older than five years.
DELETE FROM sales WHERE ordered_at < now() - INTERVAL '5 years';
Be careful when using the DELETE command without a WHERE clause. If you don't provide a condition, the command will delete all rows in the table.
DELETE FROM table_name;
Remember to always back up your data before running such commands to prevent accidental data loss.
2. Setting up a background worker: PostgreSQL supports the creation of background workers. These are processes that run in the background and can be programmed to automatically delete or archive data according to the retention schedule.
3. Using ON DELETE triggers: ON DELETE triggers can be used to remove or archive related data from different tables automatically, ensuring that data retention policies are consistently applied across the database.
Creating a trigger in PostgreSQL that runs on DELETE operations involves two steps: creating a function that encapsulates the logic to be executed and then creating a trigger that calls this function when a DELETE operation occurs.
Here's how you might do it:
Step 1: Create the function. This function will be called by the trigger. It should return type trigger.
CREATE OR REPLACE FUNCTION remove_history_of_canceled_sales()
RETURNS TRIGGER AS $$
BEGIN
IF ( OLD.data->>sales_status <> 'canceled') AND
(NEW.data->>sales_status = 'canceled') THEN
DELETE FROM user_history WHERE sales_id = OLD.sales_id;
END IF;
RETURN OLD;
END;
$$ LANGUAGE plpgsql;
In this example, the function checks if the sales status changed to 'canceled’ and removes the user_history related to that sales. The OLD keyword refers to the old value of the row that is being updated, while the NEW refers to the updated record.
Step 2: Create the trigger. This SQL statement creates a trigger that calls the function update_on_delete() before each DELETE operation on the your_table:
CREATE TRIGGER remove_user_history_from_cancel
AFTER UPDATE ON sales
FOR EACH ROW EXECUTE PROCEDURE remove_canceled_sales_history();
In this example, the trigger is executed after every update on the sales and remove_canceled_sales_history is the function that will be executed for EACH row being updated.
4. Role-based access control: Implementing role-based access control ensures that only authorized users can delete or modify data, which is crucial for maintaining data integrity and compliance with retention policies.
5. Database policies for data archival: Alongside data deletion, PostgreSQL can be used to manage data archiving, where data is moved to less frequently accessed storage while keeping it available for future reference.
Implementing these strategies in PostgreSQL requires a good understanding of the database structure and the specific data requirements of the organization. By effectively using Postgres' features, developers can ensure that their data retention practices are both efficient and compliant with organizational policies and regulations.
Built on PostgreSQL but faster, Timescale simplifies data retention by allowing you to automate your data retention policies. This functionality is particularly beneficial for managing time-series data, where older data often becomes less useful over time.
1. Automatic data retention policies: Timescale allows you to set up policies that automatically discard old data once it reaches a certain age. This is especially useful in applications where only recent data is relevant.
SELECT add_retention_policy('conditions', INTERVAL '30 days');
We’ll dive deeper into Timescale’s automatic retention policies in the next section of this article.
2. Manual chunk dropping: In addition to automatic policies, Timescale provides the flexibility to manually drop data chunks. This is useful for fine-tuning data retention and managing storage more effectively.
3. Efficient data deletion: Unlike traditional row-by-row deletion, Timescale handles data retention at the chunk level. This approach is faster and more efficient as it involves dropping entire chunks of data that fall within a specified time range. 4. Combining with continuous aggregates: You can downsample older data by combining data retention with continuous aggregates. This means you can maintain summaries of historical data without needing to store the raw data.
5. Cost management: With Timescale, you are charged based on actual storage usage. By effectively using data retention policies, compression, and tiered storage, you can significantly manage and reduce storage costs.
These features make Timescale an attractive option for developers and organizations looking to implement efficient and automated data retention strategies in their time-series applications.
Creating a data retention policy in Timescale involves a few straightforward steps:
1. Selection of hypertable: First, choose the hypertable to which you want to apply the retention policy.
2. Defining the retention duration: Decide the duration for which the data should be retained. For example, you might want to keep data for 24 hours.
3. Implementing the policy: Use the add_retention_policy function to add the policy to your chosen hypertable. For instance, to retain data in a hypertable named 'conditions' for 24 hours, you would execute: SELECT add_retention_policy('conditions', INTERVAL '24 hours');
4. Removing a policy: If you need to remove an existing policy, use the remove_retention_policy function with the hypertable's name.
5. Monitoring scheduled jobs: You can view scheduled data retention jobs and their statistics by querying the timescaledb_information.jobs and timescaledb_information.job_stats tables.
In Timescale, combining data retention with continuous aggregates allows for a more efficient management of time-series data. Continuous aggregates provide a way to automatically generate and store summarized versions of your data. As raw data ages and becomes less relevant, it can be downsampled or summarized into these aggregates, ensuring that essential information is retained while reducing storage requirements.
This approach is particularly useful for long-term data analysis where detailed historical data may not be necessary. By focusing on aggregated data over time, you can maintain a balance between data availability and storage optimization, making it ideal for trend analysis, forecasting, and other similar use cases. Check out our documentation on data retention with continuous aggregates to learn more.
While you can tier your data using Postgres, there’s a much more seamless and easier way. Timescale provides a feature for archiving data that is not actively accessed, using a multi-tiered storage architecture called Tiered Storage. This is done by creating a tiering policy, which automatically moves data to the object storage tier based on a specified move_after threshold.
1. Use add_tiering_policy function: This function allows you to specify the hypertable and the time interval after which the data should be moved to object storage.
2. Removing a policy: If you need to remove a tiering policy, you can use the remove_tiering_policy function.
The tiering process is asynchronous, meaning data is not moved immediately but scheduled.
You can continue to query your data during the migration process.
This approach helps in cost-effective data management, especially for older data that is not frequently accessed but still needs to be retained.
Check out the Timescale Docs on creating a tiering policy to learn more.
In this blog post, we've explored the crucial aspects of data retention policies, their importance, and implementation in modern database systems like PostgreSQL and Timescale. We've learned that data retention policies are vital for regulatory compliance, data management efficiency, legal protection, and cost management. They also greatly benefit developers by streamlining data management and enhancing data security.
Timescale's Tiered Storage system offers a sophisticated and cost-effective approach to archiving data, enabling efficient data storage and accessibility. The creation of tiering policies automates the archival of less frequently accessed data, optimizing storage costs and operational efficiency.
A well-structured data retention policy is not just a compliance requirement but a strategic asset in data management. Tools like Timescale offer robust solutions to implement these policies effectively, ensuring data is managed responsibly and efficiently throughout its lifecycle. Try Timescale today.