Skewed join in Pig<\/h2>\n<\/div>\n<\/div>\n

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• Joining skewed<\/b>\u00a0data using apache Pig skewed join.In a distributed processing environment Data skew is a serious problem,and occurs when the data is not evenly divided among the key tuples from the map phase.<\/li>\n
• To help the data skew issue with joins Apache Pig is used.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n
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  • Using two-table skewed join works.<\/li>\n
  • Construct the join Used “skewed”‘ to force it used skewed join.\u00a0pig.skewed join.reduce.memusage<\/code><\/li>\n
  • specifies the reducer to perform the join.<\/li>\n
  • Pig forces low fraction for more reducer but increases copying cost.<\/li>\n
  • Difficult to presence Parallel joins for underlying data.<\/li>\n
  • The underlying data is sufficiently skewed, load too much of the parallelism gains.<\/li>\n
  • Skewed join does not have restriction on the size of the input keys.<\/li>\n
  • It accomplishes by dividing one of the input on the join and other input.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n
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    Implementation:<\/h2>\n<\/div>\n<\/div>\n

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    • Skewed join it translates into two map\/reduce jobs.<\/li>\n
    • The root job samples the input records and computes the underlying key space.<\/li>\n
    • The second job modules the input table and performs a join on the predicate.<\/li>\n
    • In order to join two tables, the first tables is partitioned and another is streamed to the reducer.<\/li>\n
    • The map task uses the pig.keydist file to define the number of reducers per key.<\/li>\n
    • It sends the key to each of the reducers in a round robin(RR)fashion. Skewed joins happen in the reduce phase of the join job.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"

      Answer:Joining skewed\u00a0data using apache Pig skewed join.In a distributed processing environment Data skew is a serious problem,and occurs when the data is not evenly divided among the key tuples from the map phase.<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"passster_activate_protection":false,"passster_protect_child_pages":"","passster_protection_type":"password","passster_password":"","passster_activate_overwrite_defaults":"","passster_headline":"","passster_instruction":"","passster_placeholder":"","passster_button":"","passster_id":"","passster_activate_misc_settings":"","passster_redirect_url":"","passster_hide":"no","passster_area_shortcode":"","gtb_hide_title":false,"gtb_wrap_title":false,"gtb_class_title":"","gtb_remove_headerfooter":false,"footnotes":""},"categories":[456],"tags":[195,365,491,203,199,214,209,488,205,524,485,486,222,484,490,196,526,286,527,520,207,487,217,468,489,493,367,483,522,528,523,525,529,521,492,200,197,280,364,285],"class_list":["post-157","post","type-post","status-publish","format-standard","hentry","category-apache-pig","tag-accenture-interview-questions-and-answers","tag-amazon-development-centre-india-pvt-ltd-interview-questions-and-answers","tag-applied-materials-interview-questions-and-answers","tag-capgemini-interview-questions-and-answers","tag-casting-networks-india-pvt-limited-interview-questions-and-answers","tag-cgi-group-inc-interview-questions-and-answers","tag-collabera-technologies-interview-questions-and-answers","tag-crisil-limited-interview-questions-and-answers","tag-dell-international-services-india-pvt-ltd-interview-questions-and-answers","tag-differentiate-between-replicated-skewed-and-merge-join","tag-ernst-young-interview-questions-and-answers","tag-exide-industries-interview-questions-and-answers","tag-flipkart-interview-questions-and-answers","tag-genpact-interview-questions-and-answers","tag-hexaware-technologies-interview-questions-and-answers","tag-ibm-interview-questions-and-answers","tag-joins-in-pig","tag-lt-infotech-interview-questions-and-answers","tag-map-side-join-in-pig-example","tag-merge-join-in-pig","tag-mphasis-interview-questions-and-answers","tag-myntra-designs-pvt-ltd-interview-questions-and-answers","tag-peoplestrong-interview-questions-and-answers","tag-pig-practice-questions","tag-prokarma-softech-nterview-questions-and-answers","tag-quintiles-interview-questions-and-answers","tag-rbs-india-development-centre-pvt-ltd-interview-questions-and-answers","tag-reliance-industries-ltd-interview-questions-and-answers","tag-replicated-joins-in-pig","tag-replicated-skewed-and-merge-join-in-pig","tag-skewed-join-in-pig","tag-skewed-join-in-pig-with-example","tag-skewed-join-in-pig-with-examplejoins-in-pig","tag-skewed-join-spark","tag-syngene-international-limited-interview-questions-and-answers","tag-tech-mahindra-interview-questions-and-answers","tag-unitedhealth-group-interview-questions-and-answers","tag-virtusa-consulting-services-pvt-ltd-interview-questions-and-answers","tag-wells-fargo-interview-questions-and-answers","tag-xoriant-solutions-pvt-ltd-interview-questions-and-answers"],"yoast_head":"\n