Using NumericField for dates and other numbers is likely to help a lot, and removes padding problems. I'd try that first, or just sort the top n hits yourself.
-- Ian. On Tue, Aug 17, 2010 at 8:46 PM, Michel Nadeau <aka...@gmail.com> wrote: > I could at least drop hours/mins/sec, we don't need them, so my timestamp > could become 'YYYYMMDD', that would cut the number of unique terms at least > for dates. > > What about my other question about numbers : *" We do pad our numbers with > zeros though (for example: 10 becomes 00000010, etc.) because we had trouble > with sorting (100 was smaller than 2) ; is that considered as "string > sorting" ? This might explain a part of the problem."* ? Thanks. > > - Mike > aka...@gmail.com > > > On Tue, Aug 17, 2010 at 3:40 PM, Erick Erickson > <erickerick...@gmail.com>wrote: > >> Hmmm, I glossed over your comment about sorting the top 250. There's >> no reason that wouldn't work. >> >> Well, one way for, say, dates is to store separate fields. YYYY, MM, DD, >> HH, MM, SS, MS. That gives you say, 100 year terms, + 12 month >> +31 days + .... for a very small total. You pay the price though by >> having to change your queries and sorts to respect all 6 fields... >> >> But I'd only really go there after seeing if other options don't work. >> >> >> Best >> Erick >> >> On Tue, Aug 17, 2010 at 3:35 PM, Michel Nadeau <aka...@gmail.com> wrote: >> >> > Would our approach to limit the search top 250 documents (and then sort >> > these 250 documents) work fine ? Or even 250 unique terms with a lot of >> > users is bad on memory when sorting ? >> > >> > We didn't look at trie fields - I will do though, thanks for the tip ! >> > >> > We do store the original 'Data' field (only the 'SearchableData' field is >> > analyzed, all other fields are not analyzed), the users mainly sort on >> > numeric values; not a lot on string values (in fact I could compltely >> drop >> > the sort by string feature). We do pad our numbers with zeros though (for >> > example: 10 becomes 00000010, etc.) because we had trouble with sorting >> > (100 >> > was smaller than 2) ; is that considered as "string sorting" ? This might >> > explain a part of the problem. >> > >> > Why/how would I reduce the count of unique terms? >> > >> > >> > - Mike >> > aka...@gmail.com >> > >> > >> > On Tue, Aug 17, 2010 at 3:28 PM, Erick Erickson <erickerick...@gmail.com >> > >wrote: >> > >> > > If you have tens of millions of documents, almost all with unique >> fields >> > > that you're sorting on, you'll chew through memory like there's no >> > > tomorrow. >> > > >> > > Have you looked at trie fields? See: >> > > >> > > >> > >> http://www.lucidimagination.com/blog/2009/05/13/exploring-lucene-and-solrs-trierange-capabilities/ >> > > >> > > I'm a little concerned that the user can sort on Data. Any field used >> for >> > > sorting >> > > should NOT be analyzed, so unless you are indexing "Data" unanalyzed, >> > > that's >> > > a problem. And if you are sorting on strings unique to each document, >> > > that's >> > > also a memory hog. Not to mention whether capitalization counts. >> > > >> > > You might enumerate the terms in your index for each of the sortable >> > fields >> > > to figure out what the total number of unique terms each is and use >> that >> > as >> > > a basis for reducing their count.... >> > > >> > > HTH >> > > Erick >> > > >> > > On Tue, Aug 17, 2010 at 3:05 PM, Michel Nadeau <aka...@gmail.com> >> wrote: >> > > >> > > > Hi Erick, >> > > > >> > > > Here's some more details about our structure. First here's an example >> > of >> > > > document in our index : >> > > > >> > > > PrimaryKey = SJAsfsf353JHGada66GH6 (it's a hash) >> > > > DocType = X >> > > > Data = This is the data >> > > > SearchableContent = This is the data >> > > > DateCreated = <timestamp> >> > > > DateModified = <timestamp> >> > > > Counter1 = 17 >> > > > Counter2 = 3 >> > > > Average = 0.17 >> > > > Cost = 200 >> > > > >> > > > The users are able to sort on almost all fields: Data, DateCreated, >> > > > DateModified, Counter1, Counter2, Average, Cost. >> > > > >> > > > When we search, we always search on the 'SearchableContent' field and >> > we >> > > > have at least one filter on the DocType (because we have many >> document >> > > > types >> > > > in the same index). So a common search that would find the document >> > above >> > > > is >> > > > "data *AND DocType:X*" (we automatically add the "*AND DocType:X*" >> part >> > > > using Lucene Filters. >> > > > >> > > > I would say that the number of unique terms in the field being sorted >> > on >> > > is >> > > > very big - for example timestamps, almost all unique, counters, >> > average, >> > > > cost, data... so if a query finds 10M results, it's almost 10M >> > different >> > > > values to sort. About cache and warm-up queries : we don't use >> warm-up >> > > > queries -at all- because we have absolutely no idea of what users are >> > > going >> > > > to search for (they can search for absolutely anything). About >> > "returning >> > > > 10M" documents, right, we don't actually return the 10M documents, we >> > use >> > > > pagination to return documents X to Y of the 10M (and the 10M was >> only >> > an >> > > > example, it can be anywhere between 1K and 100M results). The >> > pagination >> > > > usually works fine and fast, our problem is really sorting. >> > > > >> > > > Our "Lucene Reader" process has 2GB of ram allowed, here's how I >> start >> > it >> > > - >> > > > >> > > > java -Xmx2048m -jar LuceneReader.jar >> > > > >> > > > The problem really seems to be a ram problem, but I can't be 100% >> sure >> > > (any >> > > > help about how to be sure is welcome). >> > > > >> > > > Our current idea of a solution would be to get maximum 250 results >> (the >> > > > more >> > > > relevant ones; more results than that is totally useless in our >> system) >> > > so >> > > > the sort should work fine on a small data set like that, but we want >> to >> > > > make >> > > > sure we're doing everything right before doing that so we don't run >> in >> > > the >> > > > same problems again. >> > > > >> > > > Thank you very much; let me know if you need any more details! >> > > > >> > > > - Mike >> > > > aka...@gmail.com >> > > > >> > > > >> > > > On Mon, Aug 16, 2010 at 4:01 PM, Erick Erickson < >> > erickerick...@gmail.com >> > > > >wrote: >> > > > >> > > > > Let's back up a minute. The number of matched records is not >> > > > > important when sorting, what's important is the number of unique >> > > > > terms in the field being sorted. Do you have any figures on that? >> One >> > > > > very common sorting issue is sorting on very fine date time >> > > resolutions, >> > > > > although your examples don't include that... >> > > > > >> > > > > Now, cache loading is an issue. The very first time you sort on a >> > > field, >> > > > > all the values are read into a cache. Is it possible this is the >> > source >> > > > > of your problems? You can cure this with warmup queries. The >> > take-away >> > > > > is that measuring the response time for the first sorted query is >> > > > > very misleading. >> > > > > >> > > > > Although if you're sorting on many, many, many email addresses, >> > > > > that could be "interesting". >> > > > > >> > > > > The comment "returning 10,000,000 documents" is, I hope, a >> > > > > misstatement. If you're trying to *return* 10M docs sorting >> > > > > is irrelevant compared to assembling that many documents. If >> > > > > you're trying to return the first 100 of 10M documents, it should >> > > > > work. >> > > > > >> > > > > Overall, we need more details on what you're sorting and what >> > > > > you're trying to return as well as how you're measuring before >> > > > > we can say much.... >> > > > > >> > > > > Along with how much memory you're giving your JVM to work with, >> > > > > what "exploding" means. Are you CPU bound? IO bound? Swapping? >> > > > > You need to characterize what is going wrong before worrying about >> > > > > solutions...... >> > > > > >> > > > > Best >> > > > > Erick >> > > > > >> > > > > On Mon, Aug 16, 2010 at 3:08 PM, Michel Nadeau <aka...@gmail.com> >> > > wrote: >> > > > > >> > > > > > Hi, >> > > > > > >> > > > > > we are building an application using Lucene and we have HUGE data >> > > sets >> > > > > (our >> > > > > > index contains millions and millions and millions of documents), >> > > which >> > > > > > obviously cause us very important problems when sorting. In fact, >> > we >> > > > > > disabled sorting completely because the servers were just >> exploding >> > > > when >> > > > > > trying to sort results in RAM. The users using the system can >> > search >> > > > for >> > > > > > whatever they want, so we never know how many results will be >> > > returned >> > > > - >> > > > > a >> > > > > > search can return 10 documents (no problem with sorting) or >> > > 10,000,000 >> > > > > > (huge >> > > > > > sorting problems). >> > > > > > >> > > > > > I woke up this morning and had a flash : is it possible with >> Lucene >> > > to >> > > > > have >> > > > > > a "natural sorting" of documents? For example, let's say I have 3 >> > > > columns >> > > > > I >> > > > > > want to be able to sort by : first name, last name, email; I >> would >> > > have >> > > > 3 >> > > > > > different indexes with the very same data but with a different >> > > primary >> > > > > key >> > > > > > for sorting. I know it's far fetched, and I have never seen >> > anything >> > > > like >> > > > > > that since I use Lucene, but we're just desperate... how people >> do >> > to >> > > > > have >> > > > > > huge data sets, a lot of users, and sort!? >> > > > > > >> > > > > > Thanks, >> > > > > > >> > > > > > Mike >> > > > > > >> > > > > >> > > > >> > > >> > >> > --------------------------------------------------------------------- To unsubscribe, e-mail: java-user-unsubscr...@lucene.apache.org For additional commands, e-mail: java-user-h...@lucene.apache.org
