Tell me about the main processes of PostgreSQL.

PostgreSQL has several key processes that ensure the database management system (DBMS) operates:

• Postmaster (main process) — starts and controls all other processes, accepts client connections.
• Backend processes — created for each client connection, handle requests.
• WAL Writer — responsible for writing transaction logs (Write-Ahead Logging) to disk.
• Checkpoint process — periodically flushes changed pages from the buffer to disk to reduce recovery time.
• Background Writer — handles background flushing of changed pages to the database to improve performance.
• Autovacuum daemon — automatically cleans and reorganizes tables to prevent bloat and maintain statistics.
• Stats Collector — gathers server operation statistics for the query optimizer.

These processes together ensure the reliability, performance, and consistency of data in PostgreSQL.