pig tutorial - apache pig tutorial - Splitting input into substrings in PIG (Hadoop) ? - pig latin - apache pig - pig hadoop
What is substring ?
- A substring of a string is a string that occurs "in" . For example, "the best of" is a substring of "It was the best of times".
- This is not to be confused with subsequence, which is a generalization of substring. For example, "Itwastimes" is a subsequence of "It was the best of times", but not a substring.
What is hadoop ?
- Hadoop is an open source, Java-based programming framework that supports the processing and storage of extremely large data sets in a distributed computing environment
- On Hadoop system using Apache Pig you can write very simple code that will split file on the fly. we will have the flexibility to control flow of data and do manipulations (if any) and split file.
Now we see how to split file into individual files using Pig Script. Here is our sample file
TEST.DEV.ENV.SAMPLE.FILE:
HEADER1DIBBCCLY8-9568347556434756972CMMS21WUE
000001010K1DIBB 7RHUN 2100000AE J82V 2269167AD 2002-03-079999-12-31+000000000100000 22004-02-28-20.00.13.106749
000002010K1DIBB 7RHUN 2100000AE J82V 2269167AD 2002-03-072004-07-30+000000000100000 32004-02-28-20.00.13.106749
9TRAILR1DIBBCCLY8-95683475564347560000084<br>
HEADERVV9IHFYSKN-4654178251104433898CMMS21ANI
0000030108VV9IH AKB7L 3300000AE XMV9 2269167AD 2002-03-059999-12-31+000000000100000 22004-02-28-20.00.13.106749
0000040108VV9IH AKB7L 3300000SE XMV9 2269167AD 2002-03-052004-07-30+000000000100000 32004-02-28-20.00.13.106749
9TRAILRVV9IHFYSKN-46541782511044330000510<br>
HEADERLY674FBNR4-9375012333185998800CMMS21AIZ
000005010ULY674 5XWJR 0100000SE XMV9 2269167AD 2002-03-059999-12-31+000000000100000 22004-02-28-20.00.13.106749
000006010ULY674 5XWJR 0100000AE XMV9 2269167AD 2002-03-052004-07-30+000000000100000 32004-02-28-20.00.13.106749
9TRAILRLY674FBNR4-93750123331859980000150<br>
HEADERT0X36Q6YVQ-5632769394873798290CMMS21WLO
000007010QT0X36 RJPWK 5500000AE J82V 2269167AD 2002-10-229999-12-31+000000000100000 22004-02-28-20.00.13.106749
000008010QT0X36 RJPWK 5500000AE J82V 2269167AD 2002-10-222004-07-30+000000000100000 32004-02-28-20.00.13.106749
9TRAILRT0X36Q6YVQ-56327693948737980000642<br>
HEADER8LIKAC67U9-2737265552238819829CMMS21HMV
000009010S8LIKA 07L1X 4400000BE J82V 2269167AD 2002-03-079999-12-31+000000000100000 22004-02-28-20.00.13.106749
000010010S8LIKA 07L1X 4400000BE J82V 2269167AD 2002-03-072004-07-30+000000000100000 32004-02-28-20.00.13.106749
9TRAILR8LIKAC67U9-27372655522388190000412<br>
HEADERAS7G3QPIUC-8825934656338659366CMMS21BQA
000011010QAS7G3 CO46Q 8500000BE RI12 2269167AD 2002-03-059999-12-31+000000000100000 22004-02-28-20.00.13.106749
000012010QAS7G3 CO46Q 8500000BE RI12 2269167AD 2002-03-052004-07-30+000000000100000 32004-02-28-20.00.13.106749
9TRAILRAS7G3QPIUC-88259346563386590000865- In the sample file if we see there are lot of headers and trailers and some data between them. Our requirement is to split each set of data with HEADER, TRAILER and DETAIL DATA into individual files. For our sample it should generate 6 different files.
- We will split file using key values in the file. Here we use positions 11-15 (5 characters) in DETAIL DATA and positions 8-12 in HEADER and TRAILER data. We must maintain the consistency of the data as Header row, Details rows and Trailer row.
- This makes the complete structure of file and keeps all data together.
Now we write Pig Script to split the file -
REGISTER /home/jars/pig/piggybank.jar;
A = LOAD '/path/to/input/file/TEST.DEV.ENV.SAMPLE.FILE'
USING PigStorage('\t') AS (line:chararray);
B = FILTER A BY SUBSTRING(line, 1, 7) != 'HEADER' AND SUBSTRING(line, 0, 7) != '9TRAILR';
C = FILTER A BY SUBSTRING(line, 1, 7) == 'HEADER' OR SUBSTRING(line, 0, 7) == '9TRAILR';
-- Extract data based on key value from Header, Details and Trailer rows
D = GROUP B BY SUBSTRING($0, 10, 15);
E = GROUP C BY SUBSTRING($0, 7, 12);
F = UNION D, E;
G = FOREACH F GENERATE FLATTEN($0), FLATTEN($1);
SPLIT G INTO H IF SIZE($0) > 0, X IF SIZE($0) <= 0;
J = ORDER H BY $1;
STORE J INTO '/path/to/output/directory'
-- Stores using \t as the input separator
USING org.apache.pig.piggybank.storage.MultiStorage('/path/to/output/directory', '0');- File is split on the value we taken as key value. Here our key value from all rows (Header, Details and Trailer) is 5 characters specified using function substring() at transformtions ‘D’ and ‘E’.
Now we will see output directory for files -
Learn Apache pig - Apache pig tutorial - Pig split string example - Apache pig examples - Apache pig programs
Learn Apache pig - Apache pig tutorial - Pig Substring - Apache pig examples - Apache pig programs
Learn Apache pig - Apache pig tutorial - Split in pig - Apache pig examples - Apache pig programs