Hi Tom, On 2014-06-06 15:44:25 -0400, Tom Lane wrote: > I figured it'd be easy enough to get a better estimate by adding another > counter to count just LIVE and INSERT_IN_PROGRESS tuples (thus effectively > assuming that in-progress inserts and deletes will both commit).
Did you plan to backpatch that? My inclination would be no... > I did > that, and found that it helped Tim's test case not at all :-(. A bit of > sleuthing revealed that HeapTupleSatisfiesVacuum actually returns > INSERT_IN_PROGRESS for any tuple whose xmin isn't committed, regardless of > whether the transaction has since marked it for deletion: > > /* > * It'd be possible to discern between INSERT/DELETE in progress > * here by looking at xmax - but that doesn't seem beneficial for > * the majority of callers and even detrimental for some. We'd > * rather have callers look at/wait for xmin than xmax. It's > * always correct to return INSERT_IN_PROGRESS because that's > * what's happening from the view of other backends. > */ > return HEAPTUPLE_INSERT_IN_PROGRESS; > > It did not use to blow this question off: back around 8.3 you got > DELETE_IN_PROGRESS if the tuple had a delete pending. I think we need > less laziness + fuzzy thinking here. Maybe we should have a separate > HEAPTUPLE_INSERT_AND_DELETE_IN_PROGRESS result code? Is it *really* > the case that callers other than VACUUM itself are okay with failing > to make this distinction? I'm dubious: there are very few if any > callers that treat the INSERT and DELETE cases exactly alike. My current position on this is that we should leave the code as is <9.4 and HEAPTUPLE_INSERT_IN_PROGRESS for the 9.4/master. Would you be ok with that? The second best thing imo would be to discern and return HEAPTUPLE_INSERT_IN_PROGRESS/HEAPTUPLE_DELETE_IN_PROGRESS for the respective cases. Which way would you like to go? Greetings, Andres Freund -- Andres Freund http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (email@example.com) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers