OLAP Workloads on PostgreSQL: A Guide
Written by Juan José Gouvêa
Online analytical processing (OLAP) offers sophisticated data analysis capabilities at scale, enabling organizations to gain deep insights from complex datasets. Traditionally, OLAP systems have been challenging to integrate and manage due to their specialized architectures and query languages. However, implementing OLAP functionality on a common relational database like PostgreSQL can simplify setup and integration with existing systems.
While PostgreSQL is a powerful and versatile relational database, it can struggle with the demands of OLAP workloads out of the box. However, with the right tools and extensions (and we all know how PostgreSQL has many tricks up its sleeve 🪄), PostgreSQL can compete with leading OLAP solutions, offering both performance and familiarity.
In this guide, we will go through the following checklist:
Understand what OLAP workloads entail
Explore how OLAP works in PostgreSQL
Examine the challenges of OLAP on PostgreSQL
Learn about tools that enhance PostgreSQL's OLAP performance
What Is an OLAP Workload?
First, the basics. Online analytical processing (OLAP) is a data analytics approach designed to answer complex queries swiftly. OLAP systems enable multidimensional analysis of large volumes of data from multiple sources, facilitating activities like business reporting, data mining, and trend analysis.
OLAP and data cubes
At the core of OLAP is the concept of the data cube, a multidimensional array of data that allows for efficient querying and analysis across multiple dimensions. Unlike traditional relational databases that store data in two-dimensional tables (rows and columns), data cubes can handle three or more dimensions, such as time, geography, and product categories.
For example, a data cube might include dimensions like:
Time dimension: years, quarters, months
Product dimension: product categories, individual products
Location dimension: regions, countries, cities
This structure enables users to perform complex queries that aggregate and analyze data across multiple dimensions simultaneously.
In modern database and data warehousing systems, however, these concepts have evolved. Instead of relying on pre-calculated data cubes that require storage and maintenance, modern platforms use real-time multidimensional calculations powered by advanced query engines and columnar storage.
The power of OLAP
The multidimensional nature of OLAP makes it highly effective for analyzing data at different levels of granularity. By organizing data into cubes, OLAP systems can process queries that involve multiple dimensions more efficiently than traditional relational databases.
Benefits of OLAP:
Multidimensional analysis: Examine data across various dimensions and hierarchies.
Complex calculations: Perform advanced calculations like trend analysis and forecasting.
Fast query performance: Optimize queries for quick response times, even with large data sets.
How OLAP Works in PostgreSQL
When it comes to OLAP implementations, you have two main paths: specialized OLAP tools or adapting PostgreSQL. Specialized OLAP databases like ClickHouse are built around data cubes and optimized specifically for analytical queries. They come with their own query languages and are very efficient for their intended use cases.
However, many organizations prefer to leverage PostgreSQL for OLAP workloads through what's known as ROLAP (relational OLAP) architecture. This approach stores data in traditional relational structures but uses analytical frameworks to transform this data into cube structures during analysis. The main advantage? You get to keep PostgreSQL's robust, well-understood backend while still accessing OLAP's analytical power.
Let’s dive deeper into these two options.
Specialized OLAP tools
Traditionally, OLAP workloads have been handled by specialized tools and databases designed specifically for multidimensional analysis.
Structure: These databases utilize data cubes optimized for storage and querying.
Examples: ClickHouse, Apache Kylin.
Function: Provide languages or interfaces optimized for querying data cubes.
Examples: MDX (Multidimensional Expressions), ClickHouse's SQL-like language.
While these systems are powerful for OLAP workloads, they come with limitations:
Specialized optimization: Tailored for specific types of queries, which can hinder performance on general workloads.
Integration challenges: Uncommon architectures and query languages can make integration with existing systems difficult.
Learning curve: Require specialized knowledge to set up and manage.
OLAP on PostgreSQL
To overcome these challenges, organizations have explored implementing OLAP workloads on relational databases like PostgreSQL. As mentioned, this approach is often referred to as ROLAP.
What is ROLAP?
ROLAP uses relational databases to store data while providing OLAP capabilities through an analytic layer that simulates multidimensional data structures.
Key characteristics of ROLAP:
ROLAP benefits:
Leverages existing relational database infrastructure.
Provides a familiar SQL interface for querying data.
Scalable and flexible for large datasets.
The OLAP challenge in PostgreSQL
PostgreSQL's greatest strength—its generalist nature—can become a limitation when handling OLAP workloads. The database engine is designed to handle any possible query pattern, and despite its numerous advantages, PostgreSQL faces challenges when handling OLAP workloads.
Complex queries: OLAP analyses often involve complex, multi-dimensional queries that can strain PostgreSQL's query planner.
Performance: Without optimization, PostgreSQL may exhibit slower performance on high-dimensional data compared to specialized OLAP systems.
Indexing: Standard indexing strategies may not suffice for the types of queries OLAP workloads generate.
Let’s look at these challenges in more detail and see how you can overcome them.
Challenges of OLAP on PostgreSQL
Query complexity vs. generalization
PostgreSQL is designed as a general-purpose relational database, optimized to handle a wide variety of queries and workloads. This generality means that it will deliver:
Flexible query handling: As a complex database engine, PostgreSQL can process and deliver high performance for many types of queries. If you’re working with huge datasets, though, your queries can become slow.
Optimization trade-offs: Specialized OLAP databases optimize for complex aggregations and multi-dimensional analyses, which can outperform PostgreSQL in those areas.
High-dimensional data
OLAP workloads often involve high-dimensional data with complex relationships. PostgreSQL's traditional row-based storage can be less efficient for such data because of the following:
Specialized OLAP tools outperform PostgreSQL in specific areas
While PostgreSQL excels in general-purpose workloads, specialized OLAP tools like ClickHouse are designed to handle complex analytical queries more efficiently.
Columnar storage. ClickHouse uses columnar storage, which can speed up queries that involve aggregations over specific columns.
Vectorized execution, which optimizes CPU usage during query processing.
Sparse indexes, using index structures optimized for read-heavy workloads.
PostgreSQL OLAP Performance
Despite these challenges, PostgreSQL can perform competitively with the right optimizations and tools.
Benchmark comparison
A benchmark comparison between PostgreSQL (with the TimescaleDB extension) and ClickHouse illustrates the performance differences in various query types.
Observations:
Complex queries: ClickHouse outperforms PostgreSQL in complex queries involving double grouping and group-by ordering due to its specialized optimizations.
General queries: PostgreSQL (with TimescaleDB) outperforms ClickHouse in most other query types, demonstrating its efficiency in general-purpose workloads. (Note: TimescaleDB has introduced new functionality to improve its performance for real-time analytics.)
Extending PostgreSQL for OLAP Workloads
PostgreSQL can be extended with tools and extensions that enhance its capabilities to bridge the performance gap for some OLAP workloads, such as real-time analytics.
Using TimescaleDB for OLAP
TimescaleDB, available as an open-source time-series database built on PostgreSQL or as a mature managed PostgreSQL platform via Timescale Cloud, designed to handle large-scale data workloads efficiently.
How TimescaleDB enhances PostgreSQL
Columnar compression: TimescaleDB implements advanced compression algorithms that reduce storage footprint and improve query performance, similar to OLAP cube systems.
Hybrid storage: It combines row-based and columnar storage, optimizing for both write and read performance.
Time-series optimizations: TimescaleDB provides functions and features specifically designed for time-series data, which is common in OLAP workloads.
Benefits for OLAP workloads
Improved performance: TimescaleDB rivals OLAP-specific databases in performance for most queries.
Familiar interface: It maintains the ease of use and familiarity of PostgreSQL.
Scalability: It can handle large volumes of data efficiently.
Additional TimescaleDB features
Real-time analytics with continuous aggregates
To learn more about how continuous aggregates help solve PostgreSQL’s limitations with real-time analytics, check out this blog post.
Integration with vector databases
An open-source stack for AI applications and advanced analytics: TimescaleDB also helps extend PostgreSQL to support vector data types (via pgvector, pgai, and pgvectorscale), enabling advanced analytics and machine learning applications. You can leverage Timescale’s AI capabilities to incorporate AI and machine learning into your data analysis pipelines.
Conclusion
OLAP workloads require specialized support to unlock their full potential for multidimensional data analysis. While PostgreSQL may not be optimized for OLAP out of the box, extensions like TimescaleDB enable it to handle some OLAP workloads—namely real-time analytics—efficiently.
By extending PostgreSQL with the right tools, you can achieve performance that rivals specialized OLAP databases, all while maintaining the familiarity and versatility of PostgreSQL. This approach simplifies integration, reduces the learning curve, and leverages existing infrastructure. Create a free Timescale account today and start making the most of PostgreSQL for your real-time analytics needs. Self-hosting is also an option.
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