I don't get what you're saying. If you want to loop over your entire range of keys, you can do it with a range query, and start and finish will both be "". Is there any scenario where you would want to do a range query where start and/or finish do not equal "", if you use random partitioning?
2010/6/9 Philip Stanhope <pstanh...@wimba.com> > I feel that there is a significant bit of confusion here. > > You CAN use start/finish when using get_range_slices with random > partitioner. But you can't make any assumptions about what key will be next > in the range which is the whole point of "random". If you do know a specific > key that you care about, you can use that as a start, but again, you don't > know what will come next. > > If you have a CF with 1M keys ... you can effectively do a full row scan > ... it is expensive and you'd have to ask yourself why you'd be wanting to > do this in the first place. > > Ordering with columns for a particular key is completely dependent on the > CompareWith choice you make when you defined the column family. For example, > you can make assumptions about the sequencing of columns returned from > get_slice (NOT get_range_slices). > > -phil > > On Jun 9, 2010, at 7:29 AM, David Boxenhorn wrote: > > To use start and finish parameters at all, you need to use OPP. Start and > finish parameters don't work if you don't use OPP, i.e. the result set won't > be: start =< resultSet < finish > > 2010/6/9 Ben Browning <ben...@gmail.com> > >> OPP stands for Order-Preserving Partitioner. For more information on >> partitioners, look here: >> >> http://wiki.apache.org/cassandra/StorageConfiguration#Partitioner >> >> To do key range slices that use both start and finish parameters and >> retrieve keys in-order, you need to use an ordered partitioner - >> either the built-in OPP or your own custom one. >> >> Ben >> >> On Tue, Jun 8, 2010 at 10:26 PM, sina <ywf2...@sina.com> wrote: >> > what's the mean of opp? And How can i make the "start" and "finish" >> useful >> > and make sense? >> > >> > >> > 2010-06-09 >> > ________________________________ >> > 9527 >> > ________________________________ >> > 发件人： Ben Browning >> > 发送时间： 2010-06-02 21:08:57 >> > 收件人： user >> > 抄送： >> > 主题： Re: Range search on keys not working? >> > They exist because when using OPP they are useful and make sense. >> > On Wed, Jun 2, 2010 at 8:59 AM, David Boxenhorn <da...@lookin2.com> >> wrote: >> >> So why do the "start" and "finish" range parameters exist? >> >> >> >> On Wed, Jun 2, 2010 at 3:53 PM, Ben Browning <ben...@gmail.com> wrote: >> >>> >> >>> Martin, >> >>> >> >>> On Wed, Jun 2, 2010 at 8:34 AM, Dr. Martin Grabmüller >> >>> <martin.grabmuel...@eleven.de> wrote: >> >>> > I think you can specify an end key, but it should be a key which >> does >> >>> > exist >> >>> > in your column family. >> >>> >> >>> >> >>> Logically, it doesn't make sense to ever specify an end key with >> >>> random partitioner. If you specified a start key of "aaa" and and end >> >>> key of "aac" you might get back as results "aaa", "zfc", "hik", etc. >> >>> And, even if you have a key of "aab" it might not show up. Key ranges >> >>> only make sense with order-preserving partitioner. The only time to >> >>> ever use a key range with random partitioner is when you want to >> >>> iterate over all keys in the CF. >> >>> >> >>> Ben >> >>> >> >>> >> >>> > But maybe I'm off the track here and someone else here knows more >> about >> >>> > this >> >>> > key range stuff. >> >>> > >> >>> > Martin >> >>> > >> >>> > ________________________________ >> >>> > From: David Boxenhorn [mailto:da...@lookin2.com] >> >>> > Sent: Wednesday, June 02, 2010 2:30 PM >> >>> > To: user@cassandra.apache.org >> >>> > Subject: Re: Range search on keys not working? >> >>> > >> >>> > In other words, I should check the values as I iterate, and stop >> >>> > iterating >> >>> > when I get out of range? >> >>> > >> >>> > I'll try that! >> >>> > >> >>> > On Wed, Jun 2, 2010 at 3:15 PM, Dr. Martin Grabmüller >> >>> > <martin.grabmuel...@eleven.de> wrote: >> >>> >> >> >>> >> When not using OOP, you should not use something like 'CATEGORY/' >> as >> >>> >> the >> >>> >> end key. >> >>> >> Use the empty string as the end key and limit the number of >> returned >> >>> >> keys, >> >>> >> as you did with >> >>> >> the 'max' value. >> >>> >> >> >>> >> If I understand correctly, the end key is used to generate an end >> token >> >>> >> by >> >>> >> hashing it, and >> >>> >> there is not the same correspondence between 'CATEGORY' and >> 'CATEGORY/' >> >>> >> as >> >>> >> for >> >>> >> hash('CATEGORY') and hash('CATEGORY/'). >> >>> >> >> >>> >> At least, this was the explanation I gave myself when I had the >> same >> >>> >> problem. >> >>> >> >> >>> >> The solution is to iterate through the keys by always using the >> last >> >>> >> key >> >>> >> returned as the >> >>> >> start key for the next call to get_range_slices, and the to drop >> the >> >>> >> first >> >>> >> element from >> >>> >> the result. >> >>> >> >> >>> >> HTH, >> >>> >> Martin >> >>> >> >> >>> >> ________________________________ >> >>> >> From: David Boxenhorn [mailto:da...@lookin2.com] >> >>> >> Sent: Wednesday, June 02, 2010 2:01 PM >> >>> >> To: user@cassandra.apache.org >> >>> >> Subject: Re: Range search on keys not working? >> >>> >> >> >>> >> The previous thread where we discussed this is called, "key is >> sorted?" >> >>> >> >> >>> >> >> >>> >> On Wed, Jun 2, 2010 at 2:56 PM, David Boxenhorn <da...@lookin2.com >> > >> >>> >> wrote: >> >>> >>> >> >>> >>> I'm not using OPP. But I was assured on earlier threads (I asked >> >>> >>> several >> >>> >>> times to be sure) that it would work as stated below: the results >> >>> >>> would not >> >>> >>> be ordered, but they would be correct. >> >>> >>> >> >>> >>> On Wed, Jun 2, 2010 at 2:51 PM, Torsten Curdt <tcu...@vafer.org> >> >>> >>> wrote: >> >>> >>>> >> >>> >>>> Sounds like you are not using an order preserving partitioner? >> >>> >>>> >> >>> >>>> On Wed, Jun 2, 2010 at 13:48, David Boxenhorn <da...@lookin2.com >> > >> >>> >>>> wrote: >> >>> >>>> > Range search on keys is not working for me. I was assured in >> >>> >>>> > earlier >> >>> >>>> > threads >> >>> >>>> > that range search would work, but the results would not be >> ordered. >> >>> >>>> > >> >>> >>>> > I'm trying to get all the rows that start with "CATEGORY." >> >>> >>>> > >> >>> >>>> > I'm doing: >> >>> >>>> > >> >>> >>>> > String start = "CATEGORY."; >> >>> >>>> > . >> >>> >>>> > . >> >>> >>>> > . >> >>> >>>> > keyspace.getSuperRangeSlice(columnParent, slicePredicate, >> start, >> >>> >>>> > "CATEGORY/", max) >> >>> >>>> > . >> >>> >>>> > . >> >>> >>>> > . >> >>> >>>> > >> >>> >>>> > in a loop, setting start to the last key each time - but I'm >> >>> >>>> > getting >> >>> >>>> > rows >> >>> >>>> > that don't start with "CATEGORY."!! >> >>> >>>> > >> >>> >>>> > How do I get all rows that start with "CATEGORY."? >> >>> >>> >> >>> >> >> >>> > >> >>> > >> >> >> >> >> > __________ Information from ESET NOD32 Antivirus, version of virus >> signature database 5164 (20100601) __________ >> > The message was checked by ESET NOD32 Antivirus. >> > http://www.eset.com >> > > >
