Hi, Le 17/04/2014 20:17, Jeff Janes a écrit : > > > If there are any open transactions (even ones that have never touched > this particular table) which started before the delete was committed, > then the vacuum was obliged to keep those deleted records around, in > case that open transaction happens to start caring about them. I > assume that the deleted rows were not randomly distributed, but rather > were concentrated in the exact range you are now inspecting. > > The reindex was also obliged to carry those deleted but not yet > uninteresting rows along to the new index. Ok, I understand now > > > > In the explain analyze output, the index scan begins at 5798.912. > What can be happening before that ? > > > The index scan reports it first *visible* row at 5798.912. Before > that, it was probably digging through thousands or millions of deleted > rows, labouriously verifying that they are not visible to it (but > still theoretically visible to someone else). Very clear explaination, thank you. > > It could be blocked on a lock or something, or you could have really > horrible IO contention that takes 5 seconds to read two blocks. But I > think the other scenario is more likely. Yes, I also think so. > > By the way, many people don't like silent cross-posting, as then we > end up unknowningly answering a question here that was already > answered elsewhere. Yes, sorry for that. I don't like it either, this was posted by a colleague of mine. One of those young foolish guys that prefer web interfaces to plain mailing-lists... Gonna scold him :-)
Best regards, Franck
