What memory parameters do you know in PostgreSQL? Tell about work_mem, shared_buffers, and effective_cache_size.

In PostgreSQL, there are several important memory parameters that affect performance:

• shared_buffers — the amount of memory allocated for the database page cache. This is the main cache PostgreSQL uses to store data in memory. It is recommended to set this to about 25-40% of total RAM.

• work_mem — the amount of memory allocated for sorting and hashing operations within a single query. If an operation requires more memory, it will use temporary files on disk, which slows down execution. The value is set per operation, so for complex queries with many operations, total consumption should be considered.

• effective_cache_size — an estimate of the amount of operating system memory available for caching files at the OS level. This parameter does not allocate memory but helps the query planner estimate the likelihood that data will be in cache and choose the optimal plan.

Proper tuning of these parameters helps improve query performance and reduce disk load.