[yvan]

It might be a newbie question, but for my own culture, what is the impact of a given snapshot if the database is really big ?

I guess it all depends on what data we are touching, but let imagine I want to update all the rows for a table with 1 billions entries, wouldn't the snapshot be giantic ?

Or maybe I misunderstood what is a snapshot.

[petereisentraut]

A snapshot is actually just a struct with a few transaction IDs (xids) and some other bookkeeping that describes which slice of the physically stored data is supposed to be visible to a transaction. The article shows the details of that. So the size of a snapshot is unrelated to the size of the database.

[yvan]

Thanks for the information. I read the article but didn't understand it well.