I have a file .txt like this
1036177 19459.7356 17380.3761 18084.1440
1045709 19674.2457 17694.8674 18700.0120
1140443 19772.0645 17760.0904 19456.7521
where the first column represent the Key and the others are the values.
I would like to normalize (min-max) each column and after that sum up the columns.
Someone can give me some advice on how do that in MapReduce?
From an algorithmic perspective you'll need to:
Mapper
Parse / tokenize each input line by it's delimiter (space?)
Use a Text object to encapsulate the key field
Either create a custom value class to encapsulate the other fields or use an ArrayWritable wrapper
Output this Key / Value from your Mapper
Reducer
All values will be grouped by the same key, so here you'll just need to process each input value and calculate the min, max and sum for each column
Finally output your result
You might want to look at using Apache Pig which should make this task much easier (untested):
grunt> A = LOAD '/path/to/data.txt' USING PigStorage(' ')
AS (key, fld1:float, fld2:float, fld3:float);
grunt> GRP = GROUP A BY key;
grunt> B = FOREACH GRP GENERATE $0, MIN(fld1), MAX(fld1), SUM(fld1),
MIN(fld2), MAX(fld2), SUM(fld2),
MIN(fld3), MAX(fld3), SUM(fld3);
grunt> STORE B INTO '/path/to/output' USING PigStorage('\t', '-schema');
Related
I have 2 data sources
1) Params.txt which has the following content
item1
item2
item2
.
.
.
itemN
2) Data.txt which which has following content
he names (aliases) of relations A, B, and C are case sensitive.
The names (aliases) of fields f1, f2, and f3 are case sensitive.
Function names PigStorage and COUNT are case sensitive.
Keywords LOAD, USING, AS, GROUP, BY, FOREACH, GENERAT
and DUMP are case insensitive. They can also be written
The task is to see if each of N items of param file exist in each line of data file.
this is the pseudocode for the same
FOREACH d IN data:
FOREACH PARAM IN PARAMS:
IF PARAM IN d:
GENERATE PARAM,1
Is something of this sort possible in PIG scripting, if yes could you please point me in that direction.
Thanks
This is possible in Pig, but Pig is perhaps an unusual language to solve the problem!
I would approach the problem like this:
Load in Params.txt
Load in Data.txt and tokenise each line (assuming you're happy to split the text on spaces - you might need to think about what to do with punctuation)
Flatten the bag from tokenise to get one "word" per record in the relation.
Join the Params and Data relations. An inner join would give you words that are only in both.
Group the data and then count the occurrence of each word.
params = LOAD 'Params.txt' USING PigStorage() AS (param_word:chararray);
data = LOAD 'Data.txt' USING PigStorage() AS (line:chararray);
token_data = FOREACH data GENERATE TOKENIZE(line) AS words:{(word:chrarray)};
token_flat = FOREACH token_data GENERATE FLATTEN(words) AS (word);
joined = JOIN params BY param_word, token_flat BY word;
word_count = FOREACH (GROUP joined BY params::param_word) GENERATE
group AS param_word,
COUNT(joined) AS param_word_count;
I have following code in pig in which i am checking the field (srcgt & destgt in record) from main files stored in record for values as mentioned in another file(intlgt.txt) having values 338,918299,181,238 but it throws error as mentioned below. Can you please suggest how to overcome this on Apache Pig version 0.15.0 (r1682971).
Pig code:
record = LOAD '/u02/20160201*.SMS' USING PigStorage('|','-tagFile') ;
intlgtrec = LOAD '/u02/config/intlgt.txt' ;
intlgt = foreach intlgtrec generate $0 as intlgt;
cdrfilter = foreach record generate (chararray) $1 as aparty, (chararray) $2 as bparty,(chararray) $3 as dt,(chararray)$4 as timestamp,(chararray) $29 as status,(chararray) $26 as srcgt,(chararray) $27 as destgt,(chararray)$0 as cdrfname ,(chararray) $13 as prepost;
intlcdrs = FILTER cdrfilter by ( STARTSWITH(srcgt,intlgt::intlgt) or STARTSWITH(destgt,intlgt::intlgt) ) ;`
Error is:
WARN org.apache.hadoop.mapred.LocalJobRunner - job_local1939982195_0002
java.lang.Exception: org.apache.pig.backend.executionengine.ExecException: ERROR 0: Scalar has more than one row in the output. 1st : (338), 2nd :(918299) (common cause: "JOIN" then "FOREACH ... GENERATE foo.bar" should be "foo::bar") at org.apache.hadoop.mapred.LocalJobRunner$Job.runTasks(LocalJobRunner.java:462) at org.apache.hadoop.mapred.LocalJobRunner$Job.run(LocalJobRunner.java:522)
When you are using
intlcdrs = FILTER cdrfilter by ( STARTSWITH(srcgt,intlgt::intlgt) or STARTSWITH(destgt,intlgt::intlgt) );
PIG is looking for a scalar. Be it a number, or a chararray; but a single one. So pig assumes your intlgt::intlgt is a relation with one row. e.g. the result of
intlgt = foreach (group intlgtrec all) generate COUNT_STAR(intlgtrec.$0)
(this would generate single row, with the count of records in the original relation)
In your case, the intlgt contains more than one row, since you have not done any grouping on it.
Based on your code, you're trying to look for SMS messages that had an intlgt on either end. Possible solutions:
if your intlgt enteries all have the same length (e.g. 3) then generate substring(srcgt, 1, 3) as srcgtshort, and JOIN intlgt::intlgt with record::srcgtshort. this will give you the records where srcgt begins with a value from intlgt. Then repeat this for destgt.
if they have a small number of lengths (e.g. some entries have length 3, some have length 4, and some have length 5) you can do the same thing, but it would be more laborious (as a field is required for each 'length').
if the number of rows in the two relations is not too big, do a cross between them, which would create all possible combinations of rows from record and rows from intlgt. Then you can filter by STARTSWITH(srcgt, intlgt::intlgt), because the two of them are fields in the same relation. Beware of this approach, as the number of records can get HUGE!
I have generated two columns(origin and destination) out of 'n' number of columns. Now I want to generate count for these two columns combination. I am not able to get the result. I am getting error as, ERROR 1070: Could not resolve Count using imports:
Below is my script,
mydata = load '/Projects/Flightdata/1987/Rawdata' using PigStorage(',') as (year:int, month:int, dom:int, dow:int, deptime:long, crsdeptime:long, arrtime:long, crsarrtime:long, uniqcarcode:chararray, flightnum:long, tailnum:chararray, actelaptime:long, crselaptime:long, airtime:long, arrdeltime:long, depdeltime:long, origcode:chararray, destcode:chararray, dist:long, taxintime:long, taxiouttime:long, flightcancl:int, canclcode:chararray, diverted:int, carrierdel:long, weatherdel:long, nasdel:long, securitydel:long, lateaircraftdel:long);
Step2 = foreach mydata generate origcode, destcode;
grpby = group Step2 by (origcode, destcode) ;
step3 = foreach grpby generate group.origcode as source, group.destcode as destination, Count(step2);
here I want to generate count for each combination of origin and destination.
Any guidance will be helpful.
Please see the Pig documentation about case sensitivity
The names of Pig Latin functions are case sensitive.
I have a Pig latin related problem:
I have this data below (in one row):
A = LOAD 'records' AS (f1:chararray, f2:chararray,f3:chararray, f4:chararray,f5:chararray, f6:chararray);
DUMP A;
(FITKA,FINVA,FINVU,FEEVA,FETKA,FINVA)
Now I have another dataset:
B = LOAD 'values' AS (f1:chararray, f2:chararray);
Dump B;
(FINVA,0.454535)
(FITKA,0.124411)
(FEEVA,0.123133)
And I would like to get those two dataset joined. I would get corresponding value from dataset B and place that value beside the value from dataset A. So expected output is below:
FITKA 0.123133, FINVA 0.454535 and so on ..
(They can also be like: FITKA, 0.123133, FINVA, 0.454535 and so on .. )
And then I would be able to multiply values (0.123133 x 0.454535 .. and so on) because they are on the same row now and this is what I want.
Of course I can join column by column but then values appear "end of row" and then I can clean it by using another foreach generate. But, I want some simpler solution without too many joins which may cause performance issues.
Dataset A is text (Sentence in one way..).
So what are my options to achieve this?
Any help would be nice.
A sentence can be represented as a tuple and contains a bag of tuples (word, count).
Therefore, I suggest you change the way you store your data to the following format:
sentence:tuple(words:bag{wordcount:tuple(word, count)})
I have a csv file which have hundreds of columns, when I load the file into Pig, I dont want to assign each column like
A = load 'path/to/file' as (a,b,c,d,e......)
Since I'll filter a lot of them at the second step:
B = foreach A generate $0,$2,....;
But here, can I assign a name and type to each column of B? something like
B = foreach A generate $0,$2,... AS (a:int,b:int,c:float)
I tried the above code but it doesn't work.
Thanks.
You have to specify them between each comma.
B = foreach A generate $0 as a, $2 as b,...
Note that it just assumes the type that it is already.