PostgreSQL's Shared Buffer: More RAM, More Problems?

Machines with hundreds of gigabytes of RAM are commonplace nowadays. PostgreSQL's shared buffer can significantly boost performance, but its workings are less intuitive than you might expect. This article delves into PostgreSQL's buffer replacement strategy, including the clock sweep algorithm and ring buffer strategies. While a larger shared buffer might seem beneficial, performance can degrade beyond a certain threshold (e.g., 64GB) because the algorithm takes longer to scan for replaceable blocks. The article advises carefully sizing the shared buffer based on data size and system memory, avoiding overly large settings that can create bottlenecks.