Ten deadly default values in PostgreSQL configuration file


Configuring the PostgreSQL configuration file is a critical aspect of optimizing the performance, stability, and security of your database. However, it’s important to be aware of the potential pitfalls of the default values in the configuration file. Some of the default values may not be suitable for all environments or workloads, and adjusting them can significantly improve PostgreSQL’s performance. In this article, we will explore some of the deadly default values in the PostgreSQL configuration file and discuss how they can impact your database’s performance.

  1. shared_buffers:The default value of shared_buffers is typically set to a relatively low value, such as 128MB. This parameter determines the amount of memory allocated for caching data in shared memory. In many cases, this default value is too low for production environments with larger datasets. Increasing the shared_buffers value based on the available memory can improve performance by reducing disk I/O.
  2. work_mem:The default value of work_mem is typically set to 4MB. This parameter determines the amount of memory allocated for each internal sort operation or hash table. When working with complex queries or large result sets, the default value may not be sufficient and can lead to disk-based operations, affecting performance. Adjusting work_mem based on the specific workload and available memory can help optimize query performance.
  3. max_connections:The default value of max_connections is typically set to 100. This parameter determines the maximum number of concurrent connections allowed to the database. Depending on the application’s requirements, this default value may be too low or too high. It’s important to configure max_connections appropriately to avoid resource contention or excessive memory usage.
  4. effective_cache_size:The default value of effective_cache_size is typically set to 128MB. This parameter represents the estimate of the operating system’s disk cache size available to PostgreSQL. In many cases, the default value may not accurately reflect the system’s actual cache size. Adjusting effective_cache_size based on the system’s available memory can help the query planner make better decisions, resulting in improved query performance.
  5. autovacuum:The default configuration enables the autovacuum feature, which automatically manages the cleanup of dead rows and maintenance of statistics. However, the default settings may not be appropriate for all workloads. Depending on the database size and activity, adjusting autovacuum-related parameters such as autovacuum_vacuum_scale_factor and autovacuum_analyze_scale_factor may be necessary to ensure proper maintenance without impacting performance.
  6. random_page_cost:The default value of random_page_cost is typically set to 4.0. This parameter represents the cost estimation of a non-sequential (random) disk access compared to a sequential disk access. However, the actual value may vary depending on the storage system and its characteristics. It’s important to analyze the storage performance and adjust the random_page_cost value accordingly to ensure accurate query planning and execution.
  7. maintenance_work_mem:The default value of maintenance_work_mem is typically set to 64MB. This parameter determines the amount of memory allocated for maintenance operations such as VACUUM, CREATE INDEX, and ALTER TABLE. For larger databases or tables, the default value may not be sufficient, leading to slower maintenance operations. Adjusting maintenance_work_mem based on the size of the database and available memory can improve the performance of these operations.
  8. checkpoint_segments and checkpoint_timeout:The default values of checkpoint_segments and checkpoint_timeout control the frequency and mechanism of the automatic background checkpoints in PostgreSQL. Depending on the workload and write activity, the default settings may not be optimal. Adjusting these parameters can help balance the checkpoint frequency and I/O impact to ensure efficient and consistent database writes.
  9. logging_collector:By default, the logging_collector parameter is turned off, and PostgreSQL logs are written to the standard error output. However, for production environments, it’s recommended to enable logging_collector and configure appropriate log destinations and levels. This allows better management of log files, integration with log management systems, and analysis of database activity for troubleshooting and performance monitoring.
  10. ssl:If your PostgreSQL deployment requires secure connections, it’s important to configure SSL properly. The default settings for SSL are disabled, and it’s necessary to configure the necessary certificates, encryption algorithms, and SSL-related parameters to ensure secure communication between the database server and clients.


The default values in the PostgreSQL configuration file are meant to provide a reasonable starting point for most deployments. However, they may not always align perfectly with your specific requirements and workload characteristics. By understanding and evaluating the deadly default values discussed in this article, you can fine-tune your PostgreSQL configuration to better match your needs. Regular monitoring, benchmarking, and testing will help you optimize these parameters further and ensure that your PostgreSQL database operates at its best. Remember, each environment is unique, and it’s essential to tailor the configuration to your specific use case for optimal performance, stability, and security.

About Shiv Iyer 330 Articles
Open Source Database Systems Engineer with a deep understanding of Optimizer Internals, Performance Engineering, Scalability and Data SRE. Shiv currently is the Founder, Investor, Board Member and CEO of multiple Database Systems Infrastructure Operations companies in the Transaction Processing Computing and ColumnStores ecosystem. He is also a frequent speaker in open source software conferences globally.