Обсуждение: BUG #9010: partition by overrides order by in window functions
The following bug has been logged on the website: Bug reference: 9010 Logged by: Markella Skempri Email address: markella.skempri@onzo.com PostgreSQL version: 9.3.2 Operating system: Linux Centos 5.5 Description: I am trying to get a row_number / rank of a resultset according to a value that is ordered by date. However whenever I try to use the order by clause, the partition by clause seems to override the ordering and produce false row number. My data: householdid previous_day gap_finish no_of_gap_days 1 2011-08-15 2011-08-16 1 1 2011-08-16 2011-08-17 1 1 2011-08-17 2011-08-18 1 1 2011-08-18 2011-08-19 1 1 2011-08-19 2011-08-20 1 1 2011-08-20 2011-08-21 1 1 2011-08-21 2011-08-27 6 1 2011-08-27 2011-08-28 1 1 2011-08-28 2011-08-29 1 1 2011-08-29 2011-08-30 1 my query: select *, row_number() over (partition by no_of_gap_days order by gap_finish asc) as no_of_Days from temptable; the results: householdid previous_day gap_finish no_of_gap_days no_of_days 1 2011-08-15 2011-08-16 1 1 1 2011-08-16 2011-08-17 1 2 1 2011-08-17 2011-08-18 1 3 1 2011-08-18 2011-08-19 1 4 1 2011-08-19 2011-08-20 1 5 1 2011-08-20 2011-08-21 1 6 1 2011-08-27 2011-08-28 1 7 1 2011-08-28 2011-08-29 1 8 1 2011-08-29 2011-08-30 1 9 1 2011-08-21 2011-08-27 6 1 What I expect to see householdid previous_day gap_finish no_of_gap_days no_of_days 1 2011-08-15 2011-08-16 1 1 1 2011-08-16 2011-08-17 1 2 1 2011-08-17 2011-08-18 1 3 1 2011-08-18 2011-08-19 1 4 1 2011-08-19 2011-08-20 1 5 1 2011-08-20 2011-08-21 1 6 1 2011-08-27 2011-08-28 1 7 1 2011-08-21 2011-08-27 6 1 1 2011-08-28 2011-08-29 1 1 1 2011-08-29 2011-08-30 1 2 Thanks for your time
markella.skempri@onzo.com writes: > I am trying to get a row_number / rank of a resultset according to a value > that is ordered by date. However whenever I try to use the order by clause, > the partition by clause seems to override the ordering and produce false row > number. AFAICS, the behavior you're complaining about is exactly what is specified by the SQL standard. For one thing, since you've not specified any ORDER BY at the outer query level, there's no requirement for the rows to be returned in any particular order. But the main point is that the row_number is supposed to be computed within each set of rows having a distinct value of no_of_gap_days, which the actual output satisfies, and your wish-list result doesn't. So I'm pretty sure that you need to write something else than this in order to get the result you want. > What I expect to see > householdid previous_day gap_finish no_of_gap_days no_of_days > 1 2011-08-15 2011-08-16 1 1 > 1 2011-08-16 2011-08-17 1 2 > 1 2011-08-17 2011-08-18 1 3 > 1 2011-08-18 2011-08-19 1 4 > 1 2011-08-19 2011-08-20 1 5 > 1 2011-08-20 2011-08-21 1 6 > 1 2011-08-27 2011-08-28 1 7 > 1 2011-08-21 2011-08-27 6 1 > 1 2011-08-28 2011-08-29 1 1 > 1 2011-08-29 2011-08-30 1 2 Unfortunately, I can't help further, because it's not obvious to me what calculation rule you are wishing for. I could understand your example if it was ordered by date, but it isn't. regards, tom lane
markella.skempri wrote > 1 2011-08-20 2011-08-21 1 > 1 2011-08-21 2011-08-27 6 > 1 2011-08-27 2011-08-28 1 > 1 2011-08-28 2011-08-29 1 > 1 2011-08-29 2011-08-30 1 > > 1 2011-08-20 2011-08-21 1 > 1 2011-08-27 2011-08-28 1 7 > 1 2011-08-21 2011-08-27 6 1 > 1 2011-08-28 2011-08-29 1 1 > 1 2011-08-29 2011-08-30 1 2 Yes, partitioning occurs before ordering. The syntax itself suggests that. Can you explain why you expect the 27-28 row to belong to the "first" group and not the "third"? If that is a typo then you are looking for contiguous blocks with the same gap-size. Once you've identified those blocks you can then partition on them and performing your row_number. David J. -- View this message in context: http://postgresql.1045698.n5.nabble.com/BUG-9010-partition-by-overrides-order-by-in-window-functions-tp5789343p5789377.html Sent from the PostgreSQL - bugs mailing list archive at Nabble.com.