ピッグラテン各グループ属性に適用される制限演算子

Question

各州の人口に基づいて最大5つの場所を返そうとしています。私はまた、州ごとの結果をソートしようとしています。それぞれの州の場所は、人口の降順に並べられています。私が現在持っているものは、州の最初の5ヵ所だけで、ではなく、の5つの最も大きな場所はそれぞれの州ごとにです。コードスニペットの下

-- Groups places by state name. 
group_by_state_name_populated_place_name = 
    GROUP project_using_state_name 
    BY (state::name, place::name); 

-- Counts population for each place in every state. 
count_population_for_each_place_in_every_state = 
    FOREACH group_by_state_name_populated_place_name 
    GENERATE group.state::name AS state_name, 
      group.place::name AS name, 
      COUNT(project_using_state_name.population) AS population; 

-- Orders population in each group found above to enable the use of limit. 
order_groups_of_states_and_population = 
    ORDER count_population_for_each_place_in_every_state 
    BY state_name ASC, population DESC, name ASC; 

-- Limit the top 5 population for each state BUT currently returning just the first 5 tuples of the previous one and not 5 of each state. 
limit_population = 
    LIMIT order_groups_of_states_and_population 5; 

Answer 1

inp_data = load 'input_data.csv' using PigStorage(',') AS (state:chararray,place:chararray,population:long); 

req_stats = FOREACH(GROUP inp_data BY state) { 
    ordered = ORDER inp_data BY population DESC; 
    required = LIMIT ordered 5; 
    GENERATE FLATTEN(required); 
}; 

req_stats_ordered = ORDER req_stats BY state, population DESC; 

DUMP req_stats_ordered;