to_tuple = FOREACH order_ip_segs GENERATE tag, FLATTEN(order_seq); result = foreach totuple GetProvinceNameFromIPNum(toSearch, * );
2011/12/18 唐亮 <[email protected]> > Prashant Kommireddi， > How to call your UDF in PIG script? > > Thanks! > > 在 2011年12月16日 下午1:12，唐亮 <[email protected]>写道： > > > Thanks Prashant Kommireddi， > > > > But my question is: > > How to call the UDF in PIG, especially the parameters to put into the > UDF. > > > > 在 2011年12月15日 下午4:05，Prashant Kommireddi <[email protected]>写道： > > > > Not sure what you mean. Have you tried the code I forwarded? Are you > facing > >> any issues there? > >> > >> If your question is regarding binarySearch implementation, here is > >> pseudo-code'ish implementation. I have not tested this, please treat > this > >> as a general idea on how to go about accessing the elements within the > >> Tuple. > >> > >> ALSO, I am assuming you have defined schema for (inner) Tuple contents. > >> > >> public String binarySearch(Tuple tuple, long toSearch, int low, int > high) > >> { > >> if(low > high) > >> return "NOT FOUND"; //Handle this the way you would like > >> > >> if(tuple == null) > >> throw new IllegalArgumentException("Tuple is null"); //Handle > >> this the way you would like > >> > >> int mid = (low + high)/2; > >> Tuple midTuple = tuple.get(mid); > >> String tag = midTuple.get(0).toString(); > >> long ipstart = (Long)midTuple.get(1); > >> long ipend = (Long)midTuple.get(2); > >> String loc = midTuple.get(3).toString(); > >> > >> if(toSearch == ipstart) //Or ipend, I am not sure how you want to > search > >> { > >> return loc; > >> } > >> else if(toSearch < ipstart) > >> return binarySearch(tuple, low, mid - 1); > >> > >> else > >> return binarySearch(tuple, mid+1, high); > >> > >> } > >> > >> > >> > >> > >> > >> > >> > >> 2011/12/14 唐亮 <[email protected]> > >> > >> > Hi Prashant Kommireddi， > >> > > >> > If so, how should I write the UDF, especially the data types in UDF? > >> > > >> > 2011/12/15 Prashant Kommireddi <[email protected]> > >> > > >> > > When you flatten your BAG all your segments are within a single > tuple. > >> > > Something like > >> > > > >> > > ((tag, ipstart, ipend, loc), (tag, ipstart, ipend, loc)...(tagN, > >> > > ipstartN, ipendN, locN)) > >> > > > >> > > You can access the inner tuples positionally. > >> > > > >> > > Sent from my iPhone > >> > > > >> > > On Dec 14, 2011, at 6:28 PM, "唐亮" <[email protected]> wrote: > >> > > > >> > > > Now the question is: > >> > > > How should I put all the "IP Segments" in one TUPLE? > >> > > > > >> > > > Please help me! > >> > > > > >> > > > > >> > > > 2011/12/15 Prashant Kommireddi <[email protected]> > >> > > > > >> > > >> Michael, > >> > > >> > >> > > >> This would have no benefit over using a DistributedCache. For a > >> large > >> > > >> cluster this would mean poor performance. If the file is static > and > >> > > needs > >> > > >> to be looked-up across the cluster, DistributedCache would be a > >> better > >> > > >> approach. > >> > > >> > >> > > >> Thanks, > >> > > >> Prashant > >> > > >> > >> > > >> On Wed, Dec 14, 2011 at 11:18 AM, jiang licht < > >> [email protected]> > >> > > >> wrote: > >> > > >> > >> > > >>> If that list of ip pairs is pretty static most time and will be > >> used > >> > > >>> frequently, maybe just copy it in hdfs with a high replication > >> > factor. > >> > > >> Then > >> > > >>> use it as a look up table or some binary tree or treemap kind of > >> > thing > >> > > by > >> > > >>> reading it from hdfs instead of using distributed cache if that > >> > sounds > >> > > an > >> > > >>> easier thing to do. > >> > > >>> > >> > > >>> > >> > > >>> Best regards, > >> > > >>> Michael > >> > > >>> > >> > > >>> > >> > > >>> ________________________________ > >> > > >>> From: Dmitriy Ryaboy <[email protected]> > >> > > >>> To: [email protected] > >> > > >>> Sent: Wednesday, December 14, 2011 10:28 AM > >> > > >>> Subject: Re: Implement Binary Search in PIG > >> > > >>> > >> > > >>> hbase has nothing to do with distributed cache. > >> > > >>> > >> > > >>> > >> > > >>> 2011/12/14 唐亮 <[email protected]> > >> > > >>> > >> > > >>>> Now, I didn't use HBase, > >> > > >>>> so, maybe I can't use DistributedCache. > >> > > >>>> > >> > > >>>> And if FLATTEN DataBag, the results are Tuples, > >> > > >>>> then in UDF I can process only one Tuple, which can't implement > >> > > >>>> BinarySearch. > >> > > >>>> > >> > > >>>> So, please help and show me the detailed solution. > >> > > >>>> Thanks! > >> > > >>>> > >> > > >>>> 在 2011年12月14日 下午5:59，唐亮 <[email protected]>写道： > >> > > >>>> > >> > > >>>>> Hi Prashant Kommireddi， > >> > > >>>>> > >> > > >>>>> If I do 1. and 2. as you mentioned， > >> > > >>>>> the schema will be {tag, ipStart, ipEnd, locName}. > >> > > >>>>> > >> > > >>>>> BUT, how should I write the UDF, especially how should I set > the > >> > type > >> > > >>> of > >> > > >>>>> the input parameter? > >> > > >>>>> > >> > > >>>>> Currently, the UDF codes are as below, whose input parameter > is > >> > > >>> DataBag: > >> > > >>>>> > >> > > >>>>> public class GetProvinceNameFromIPNum extends > EvalFunc<String> { > >> > > >>>>> > >> > > >>>>> public String exec(Tuple input) throws IOException { > >> > > >>>>> if (input == null || input.size() == 0) > >> > > >>>>> return UnknownIP; > >> > > >>>>> if (input.size() != 2) { > >> > > >>>>> throw new IOException("Expected input's size is 2, but is: > " > >> + > >> > > >>>>> input.size()); > >> > > >>>>> } > >> > > >>>>> > >> > > >>>>> Object o1 = input.get(0); * // This should be the IP > you > >> > want > >> > > >>> to > >> > > >>>>> look up* > >> > > >>>>> if (!(o1 instanceof Long)) { > >> > > >>>>> throw new IOException("Expected input 1 to be Long, > >> but > >> > > >>> got " > >> > > >>>>> + o1.getClass().getName()); > >> > > >>>>> } > >> > > >>>>> Object o2 = input.get(1); *// This is the Bag of IP > >> segs* > >> > > >>>>> if (!(o2 instanceof *DataBag*)) { //* Should I change > >> it to > >> > > >>> "(o2 > >> > > >>>>> instanceof Tuple)"?* > >> > > >>>>> throw new IOException("Expected input 2 to be > >> DataBag, > >> > > >> but > >> > > >>>> got > >> > > >>>>> " > >> > > >>>>> + o2.getClass().getName()); > >> > > >>>>> } > >> > > >>>>> > >> > > >>>>> ........... other codes ........... > >> > > >>>>> } > >> > > >>>>> > >> > > >>>>> } > >> > > >>>>> > >> > > >>>>> > >> > > >>>>> > >> > > >>>>> 在 2011年12月14日 下午3:16，Prashant Kommireddi <[email protected] > >> >写道： > >> > > >>>>> > >> > > >>>>> Seems like at the end of this you have a Single bag with all > the > >> > > >>>> elements, > >> > > >>>>>> and somehow you would like to check whether an element exists > >> in > >> > it > >> > > >>>> based > >> > > >>>>>> on ipstart/end. > >> > > >>>>>> > >> > > >>>>>> > >> > > >>>>>> 1. Use FLATTEN > >> > > >> http://pig.apache.org/docs/r0.9.1/basic.html#flatten- > >> > > >>>>>> this will convert the Bag to Tuple: to_tuple = FOREACH > >> > > >>> order_ip_segs > >> > > >>>>>> GENERATE tag, FLATTEN(order_seq); ---- This is O(n) > >> > > >>>>>> 2. Now write a UDF that can access the elements positionally > >> for > >> > > >> the > >> > > >>>>>> BinarySearch > >> > > >>>>>> 3. Dmitriy and Jonathan's ideas with DistributedCache could > >> > > >> perform > >> > > >>>>>> better than the above approach, so you could go down that > >> route > >> > > >> too. > >> > > >>>>>> > >> > > >>>>>> > >> > > >>>>>> 2011/12/13 唐亮 <[email protected]> > >> > > >>>>>> > >> > > >>>>>>> The detailed PIG codes are as below: > >> > > >>>>>>> > >> > > >>>>>>> raw_ip_segment = load ... > >> > > >>>>>>> ip_segs = foreach raw_ip_segment generate ipstart, ipend, > >> name; > >> > > >>>>>>> group_ip_segs = group ip_segs all; > >> > > >>>>>>> > >> > > >>>>>>> order_ip_segs = foreach group_ip_segs { > >> > > >>>>>>> order_seg = order ip_segs by ipstart, ipend; > >> > > >>>>>>> generate 't' as tag, order_seg; > >> > > >>>>>>> } > >> > > >>>>>>> describe order_ip_segs > >> > > >>>>>>> order_ip_segs: {tag: chararray,order_seg: {ipstart: > >> long,ipend: > >> > > >>>>>> long,poid: > >> > > >>>>>>> chararray}} > >> > > >>>>>>> > >> > > >>>>>>> Here, the order_ip_segs::order_seg is a BAG, > >> > > >>>>>>> how can I transer it to a TUPLE? > >> > > >>>>>>> > >> > > >>>>>>> And can I access the TUPLE randomly in UDF? > >> > > >>>>>>> > >> > > >>>>>>> 在 2011年12月14日 下午2:41，唐亮 <[email protected]>写道： > >> > > >>>>>>> > >> > > >>>>>>>> Then how can I transfer all the items in Bag to a Tuple? > >> > > >>>>>>>> > >> > > >>>>>>>> > >> > > >>>>>>>> 2011/12/14 Jonathan Coveney <[email protected]> > >> > > >>>>>>>> > >> > > >>>>>>>>> It's funny, but if you look wayyyy in the past, I actually > >> > > >> asked > >> > > >>> a > >> > > >>>>>> bunch > >> > > >>>>>>>>> of > >> > > >>>>>>>>> questions that circled around, literally, this exact > >> problem. > >> > > >>>>>>>>> > >> > > >>>>>>>>> Dmitriy and Prahsant are correct: the best way is to make > a > >> UDF > >> > > >>>> that > >> > > >>>>>> can > >> > > >>>>>>>>> do > >> > > >>>>>>>>> the lookup really efficiently. This is what the maxmind > API > >> > > >> does, > >> > > >>>> for > >> > > >>>>>>>>> example. > >> > > >>>>>>>>> > >> > > >>>>>>>>> 2011/12/13 Prashant Kommireddi <[email protected]> > >> > > >>>>>>>>> > >> > > >>>>>>>>>> I am lost when you say "If enumerate every IP, it will be > >> > > >> more > >> > > >>>> than > >> > > >>>>>>>>>> 100000000 single IPs" > >> > > >>>>>>>>>> > >> > > >>>>>>>>>> If each bag is a collection of 30000 tuples it might not > be > >> > > >> too > >> > > >>>>>> bad on > >> > > >>>>>>>>> the > >> > > >>>>>>>>>> memory if you used Tuple to store segments instead? > >> > > >>>>>>>>>> > >> > > >>>>>>>>>> (8 bytes long + 8 bytes long + 20 bytes for chararray ) = > >> 36 > >> > > >>>>>>>>>> Lets say we incur an additional overhead 4X times this, > >> which > >> > > >>> is > >> > > >>>>>> ~160 > >> > > >>>>>>>>> bytes > >> > > >>>>>>>>>> per tuple. > >> > > >>>>>>>>>> Total per Bag = 30000 X 160 = ~5 MB > >> > > >>>>>>>>>> > >> > > >>>>>>>>>> You could probably store the ipsegments as Tuple and test > >> it > >> > > >> on > >> > > >>>>>> your > >> > > >>>>>>>>>> servers. > >> > > >>>>>>>>>> > >> > > >>>>>>>>>> > >> > > >>>>>>>>>> On Tue, Dec 13, 2011 at 8:39 PM, Dmitriy Ryaboy < > >> > > >>>>>> [email protected]> > >> > > >>>>>>>>>> wrote: > >> > > >>>>>>>>>> > >> > > >>>>>>>>>>> Do you have many such bags or just one? If one, and you > >> > > >> want > >> > > >>> to > >> > > >>>>>> look > >> > > >>>>>>>>> up > >> > > >>>>>>>>>>> many ups in it, might be more efficient to serialize > this > >> > > >>>>>> relation > >> > > >>>>>>> to > >> > > >>>>>>>>>> hdfs, > >> > > >>>>>>>>>>> and write a lookup udf that specifies the serialized > data > >> > > >> set > >> > > >>>> as > >> > > >>>>>> a > >> > > >>>>>>>>> file > >> > > >>>>>>>>>> to > >> > > >>>>>>>>>>> put in distributed cache. At init time, load up the file > >> > > >> into > >> > > >>>>>>> memory, > >> > > >>>>>>>>>> then > >> > > >>>>>>>>>>> for every ip do the binary search in exec() > >> > > >>>>>>>>>>> > >> > > >>>>>>>>>>> On Dec 13, 2011, at 7:55 PM, 唐亮 <[email protected]> > >> > > >> wrote: > >> > > >>>>>>>>>>> > >> > > >>>>>>>>>>>> Thank you all! > >> > > >>>>>>>>>>>> > >> > > >>>>>>>>>>>> The detail is: > >> > > >>>>>>>>>>>> A bag contains many "IP Segments", whose schema is > >> > > >>>>>> (ipStart:long, > >> > > >>>>>>>>>>>> ipEnd:long, locName:chararray) and the number of tuples > >> > > >> is > >> > > >>>>>> about > >> > > >>>>>>>>> 30000, > >> > > >>>>>>>>>>>> and I want to check wheather an IP is belong to one > >> > > >> segment > >> > > >>>> in > >> > > >>>>>> the > >> > > >>>>>>>>> bag. > >> > > >>>>>>>>>>>> > >> > > >>>>>>>>>>>> I want to order the "IP Segments" by (ipStart, ipEnd) > in > >> > > >>> MR, > >> > > >>>>>>>>>>>> and then binary search wheather an IP is in the bag in > >> > > >> UDF. > >> > > >>>>>>>>>>>> > >> > > >>>>>>>>>>>> If enumerate every IP, it will be more than 100000000 > >> > > >>> single > >> > > >>>>>> IPs, > >> > > >>>>>>>>>>>> I think it will also be time consuming by JOIN in PIG. > >> > > >>>>>>>>>>>> > >> > > >>>>>>>>>>>> Please help me how can I deal with it efficiently! > >> > > >>>>>>>>>>>> > >> > > >>>>>>>>>>>> > >> > > >>>>>>>>>>>> 2011/12/14 Thejas Nair <[email protected]> > >> > > >>>>>>>>>>>> > >> > > >>>>>>>>>>>>> My assumption is that 唐亮 is trying to do binary search > >> > > >> on > >> > > >>>> bags > >> > > >>>>>>>>> within > >> > > >>>>>>>>>>> the > >> > > >>>>>>>>>>>>> tuples in a relation (ie schema of the relation has a > >> > > >> bag > >> > > >>>>>>> column). > >> > > >>>>>>>>> I > >> > > >>>>>>>>>>> don't > >> > > >>>>>>>>>>>>> think he is trying to treat the entire relation as one > >> > > >> bag > >> > > >>>>>> and do > >> > > >>>>>>>>>> binary > >> > > >>>>>>>>>>>>> search on that. > >> > > >>>>>>>>>>>>> > >> > > >>>>>>>>>>>>> > >> > > >>>>>>>>>>>>> -Thejas > >> > > >>>>>>>>>>>>> > >> > > >>>>>>>>>>>>> > >> > > >>>>>>>>>>>>> > >> > > >>>>>>>>>>>>> On 12/13/11 2:30 PM, Andrew Wells wrote: > >> > > >>>>>>>>>>>>> > >> > > >>>>>>>>>>>>>> I don't think this could be done, > >> > > >>>>>>>>>>>>>> > >> > > >>>>>>>>>>>>>> pig is just a hadoop job, and the idea behind hadoop > is > >> > > >>> to > >> > > >>>>>> read > >> > > >>>>>>>>> all > >> > > >>>>>>>>>> the > >> > > >>>>>>>>>>>>>> data in a file. > >> > > >>>>>>>>>>>>>> > >> > > >>>>>>>>>>>>>> so by the time you put all the data into an array, > you > >> > > >>>> would > >> > > >>>>>>> have > >> > > >>>>>>>>>> been > >> > > >>>>>>>>>>>>>> better off just checking each element for the one you > >> > > >>> were > >> > > >>>>>>> looking > >> > > >>>>>>>>>> for. > >> > > >>>>>>>>>>>>>> > >> > > >>>>>>>>>>>>>> So what you would get is [n + lg (n)], which will > just > >> > > >> be > >> > > >>>> [n] > >> > > >>>>>>>>> after > >> > > >>>>>>>>>>>>>> putting > >> > > >>>>>>>>>>>>>> that into an array. > >> > > >>>>>>>>>>>>>> Second, hadoop is all about large data analysis, > >> > > >> usually > >> > > >>>> more > >> > > >>>>>>> than > >> > > >>>>>>>>>>> 100GB, > >> > > >>>>>>>>>>>>>> so putting this into memory is out of the question. > >> > > >>>>>>>>>>>>>> Third, hadoop is efficient because it processes this > >> > > >>> large > >> > > >>>>>>> amount > >> > > >>>>>>>>> of > >> > > >>>>>>>>>>> data > >> > > >>>>>>>>>>>>>> by splitting it up into multiple processes. To do an > >> > > >>>>>> efficient > >> > > >>>>>>>>> binary > >> > > >>>>>>>>>>>>>> search, you would need do this in one mapper or one > >> > > >>>> reducer. > >> > > >>>>>>>>>>>>>> > >> > > >>>>>>>>>>>>>> My opinion is just don't fight hadoop/pig. > >> > > >>>>>>>>>>>>>> > >> > > >>>>>>>>>>>>>> > >> > > >>>>>>>>>>>>>> > >> > > >>>>>>>>>>>>>> On Tue, Dec 13, 2011 at 1:56 PM, Thejas Nair< > >> > > >>>>>>>>> [email protected]> > >> > > >>>>>>>>>>>>>> wrote: > >> > > >>>>>>>>>>>>>> > >> > > >>>>>>>>>>>>>> Bags can be very large might not fit into memory, and > >> > > >> in > >> > > >>>> such > >> > > >>>>>>>>> cases > >> > > >>>>>>>>>>> some > >> > > >>>>>>>>>>>>>>> or all of the bag might have to be stored on disk. > In > >> > > >>> such > >> > > >>>>>>>>> cases, it > >> > > >>>>>>>>>>> is > >> > > >>>>>>>>>>>>>>> not > >> > > >>>>>>>>>>>>>>> efficient to do random access on the bag. That is > why > >> > > >>> the > >> > > >>>>>>> DataBag > >> > > >>>>>>>>>>>>>>> interface > >> > > >>>>>>>>>>>>>>> does not support it. > >> > > >>>>>>>>>>>>>>> > >> > > >>>>>>>>>>>>>>> As Prashant suggested, storing it in a tuple would > be > >> > > >> a > >> > > >>>> good > >> > > >>>>>>>>>>> alternative, > >> > > >>>>>>>>>>>>>>> if you want to have random access to do binary > search. > >> > > >>>>>>>>>>>>>>> > >> > > >>>>>>>>>>>>>>> -Thejas > >> > > >>>>>>>>>>>>>>> > >> > > >>>>>>>>>>>>>>> > >> > > >>>>>>>>>>>>>>> > >> > > >>>>>>>>>>>>>>> On 12/12/11 7:54 PM, 唐亮 wrote: > >> > > >>>>>>>>>>>>>>> > >> > > >>>>>>>>>>>>>>> Hi all, > >> > > >>>>>>>>>>>>>>>> How can I implement a binary search in pig? > >> > > >>>>>>>>>>>>>>>> > >> > > >>>>>>>>>>>>>>>> In one relation, there exists a bag whose items are > >> > > >>>> sorted. > >> > > >>>>>>>>>>>>>>>> And I want to check there exists a specific item in > >> > > >> the > >> > > >>>>>> bag. > >> > > >>>>>>>>>>>>>>>> > >> > > >>>>>>>>>>>>>>>> In UDF, I can't random access items in DataBag > >> > > >>> container. > >> > > >>>>>>>>>>>>>>>> So I have to transfer the items in DataBag to an > >> > > >>>> ArrayList, > >> > > >>>>>>> and > >> > > >>>>>>>>>> this > >> > > >>>>>>>>>>> is > >> > > >>>>>>>>>>>>>>>> time consuming. > >> > > >>>>>>>>>>>>>>>> > >> > > >>>>>>>>>>>>>>>> How can I implement the binary search efficiently > in > >> > > >>> pig? > >> > > >>>>>>>>>>>>>>>> > >> > > >>>>>>>>>>>>>>>> > >> > > >>>>>>>>>>>>>>>> > >> > > >>>>>>>>>>>>>>> > >> > > >>>>>>>>>>>>>> > >> > > >>>>>>>>>>>>> > >> > > >>>>>>>>>>> > >> > > >>>>>>>>>> > >> > > >>>>>>>>> > >> > > >>>>>>>> > >> > > >>>>>>>> > >> > > >>>>>>> > >> > > >>>>>> > >> > > >>>>> > >> > > >>>>> > >> > > >>>> > >> > > >>> > >> > > >> > >> > > > >> > > >> > > > > >
