Before starting with the book’s topic I want to explain how to set up an efficient environment and some good practice which can improve the code’s readability and quality. As somebody will notice these methods are completely opposite to the general code style trends. I’ll try to give the motivation for each rule. Anyway, in general because the SQL universe is a strange place this requires strange approach. In order to write and read effectively the SQL the coder should gain the capability to get a mental map between the query’s sections and the underlying logic.
The PostgreSQL memory at first sight looks simple. If compared with the complex structures implemented in the other DBMS to a careless reader could seem rudimentary. However, the memory and in particular the shared buffers implementation is complex and sophisticated. This chapter will dig down deep into the PostgreSQL’s memory. 3.1 The shared buffer The shared buffer is a segment allocated at cluster’s startup. Its size is determined by the GUC parameter shared_buffers and the size can be changed only restarting the cluster.
2.4 The background writer Before the spread checkpoints the only solution to ease down the IO spike caused by the checkpoint was to tweak the background writer. This process were introduced with the revolutionary PostgreSQL 8.0. The writer, as the name suggests, works in the background searching for dirty buffers to write on the data files. The writer works in rounds. When the process awakes scans the shared buffer for dirty buffers.