Understanding consistency and data loss

Digging into the PostgreSQL transaction log without thinking about consistency is impossible. In the first part of this chapter, we tried hard to explain the basic idea of the transaction log in general. You learned that it is hard, or even impossible, to keep data files in good shape without the ability to log changes beforehand.

So far, we have mostly talked about corruption. It is definitely not good to lose data files because of corrupted entries in them, but corruption is not the only issue you have to be concerned about. Two other important topics are:

• Performance
• Data loss

While these might be an obvious choice for important topics, we have the feeling that they are not well understood and honored. Therefore, they have been taken into consideration.

In our daily business as PostgreSQL consultants and trainers, we usually tend to see people who are only focused on performance.

Performance is everything. We want to be fast; tell us how to be fast&...