Thanks a lot for your suggestions. Now I understand perfectly what happens with
analyze, vacuum and toast areas. By the way, I used pgstattuple and I found it
A last question: would you know any tool like pgstattuple but doing similar
things on indexes? I am particulary interested in how an index become
fragmented.If there is not, maybe I will dig into pgstattuple code and try to
figure out how could I do similar job on indexes.