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.
The cluster in action PostgreSQL delivers his services ensuring the ACID rules are enforced at any time. This chapter will give an outlook of a ``day in the life” of a PostgreSQL’s cluster. The chapter approach is purposely generic. At this stage is very important to understand the global picture rather the technical details. After the startup When the cluster completes the startup procedure it starts accepting the connections. When a connection is successful then the postgres main process forks into a new backend process which is assigned to the connection for the connection’s lifetime.
The book is now complete. There’s still a lot to do for reviewing the writing and fixing the bad grammar. Anyway is about 107 pages and I’m pretty satisfied. I’ve worked on this document for 4 months in my spare time and I became more confident with my English during the writing. So, what’s next? I’ll spend the next couple of weeks reviewing and fixing the book. After that I’ll put the pdf on lulu.
Foreign keys A foreign key is a constraint enforced using the values another table’s field. The classical example is the tables storing the addresses and cities. We can store the addresses with the city field, inline. Being the city a duplicated value over many addresses, this will cause the table bloat by storing long strings, duplicated many and many times, alongside with the the address. Defining a table with the cities and referencing the city id in the addresses table will result in a smaller row size.
I’ve started the sixth chapter, the one on the data integrity I’ve forgotten. There are the first two parts alongside with the introduction. I’ve also updated the book on slideshare with the new cover and the last incomplete chapter for the developers. The beautiful cover is made by Chiaretta & Bon. Kudos and many thanks. I’ve also uploaded the latex sources on github for anybody to fork and review my crappy english.