PostgreSQL has several configuration parameters that control its memory usage. Here is a detailed description of some of the most important memory-related parameters:
- shared_buffers: This parameter controls the amount of memory that is used for caching data in shared memory. The shared buffers are used to store frequently accessed data, such as table and index data, reducing the number of disk I/O operations and improving performance. The value of shared_buffers should be set to a reasonable percentage of the available memory on the system, typically around 25% to 40%.
- maintenance_work_mem: This parameter controls the amount of memory used by the database for maintenance operations, such as VACUUM and ANALYZE. The maintenance_work_mem parameter should be set to a value that is large enough to allow these operations to complete efficiently, but not so large that it causes other performance problems.
- work_mem: This parameter controls the amount of memory used by individual queries for sorting and hashing operations. The work_mem parameter should be set to a value that is large enough to allow queries to complete efficiently, but not so large that it causes other performance problems.
- effective_cache_size: This parameter is used by the query planner to estimate the size of the disk cache and how much memory is available for disk caching. The value of effective_cache_size should be set to a reasonable estimate of the amount of memory available for disk caching, typically around 60% to 70% of the available memory on the system.
- temp_buffers: This parameter controls the amount of memory used for temporary buffers, such as those used for GROUP BY and JOIN operations. The temp_buffers parameter should be set to a value that is large enough to allow temporary buffers to be created efficiently, but not so large that it causes other performance problems.
- checkpoint_segments: This parameter controls the number of WAL (Write-Ahead Log) segments that are kept in memory to reduce disk I/O during checkpoints. The value of checkpoint_segments should be set to a value that balances the amount of memory used by WAL segments with the need to minimize disk I/O during checkpoints.
- max_connections: This parameter controls the maximum number of concurrent connections that are allowed to the database. The value of max_connections should be set to a value that allows enough connections to handle the maximum number of clients, but not so many that it causes performance problems.
It is important to monitor the memory usage of the database process and adjust these parameters as necessary to ensure optimal performance. The specific values for each parameter will depend on the specific requirements of the database, the available memory on the system, and other factors, so it is recommended to experiment with different values to find the optimal configuration for your system.
