<transcript><audio_142>onwards slide 27 onwards it's not going to be material for the exam so I'm just going to skip skim through it really fast uh because mvcc looks like the keys Canan be duplicate it turns out that even the primary keys if I'm using the</transcript><transcript><audio_143>scheme in which I'm updating a primary key and I have versions it'll kind of look like if you think about the implementation of B tree for typically for a primary key you would have implemented to say I can never have a duplicate key but in some sense the keys can have you may need duplicates for a</transcript><transcript><audio_144>little bit of time okay so again as I said I'm not going to go into the details for it but let you look through that and you can read the chapter in the book that talks about that but you have to worry about uh those components there's also the issue of deletes again</transcript><transcript><audio_145>I'll let you read that by yourself but there are different ways to implement the delete function by keeping a delete flag or a tombstone flag this has to do with I've got a version chain and if I delete it uh there are different ways of deleting that and sometimes it's uh it's</transcript> onwards slide 27 onwards it's not going to be material for the exam so I'm just going to skip skim through it really fast uh because mvcc looks like the keys Canan be duplicate it turns out that even the primary keys if I'm using the scheme in which I'm updating a primary key and I have versions it'll kind of look like if you think about the implementation of B tree for typically for a primary key you would have implemented to say I can never have a duplicate key but in some sense the keys can have you may need duplicates for a little bit of time okay so again as I said I'm not going to go into the details for it but let you look through that and you can read the chapter in the book that talks about that but you have to worry about uh those components there's also the issue of deletes again I'll let you read that by yourself but there are different ways to implement the delete function by keeping a delete flag or a tombstone flag this has to do with I've got a version chain and if I delete it uh there are different ways of deleting that and sometimes it's uh it's
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