PostgreSQL中固定大小的JSONB数组的聚合

Question

我正在努力在PostgreSQL数据库中的JSONB字段上进行聚合.这可能更容易用一个例子解释,所以如果创建并填充一个名为analysis2列(id和analysis)的表,如下所示: -

create table analysis (
  id serial primary key,
  analysis jsonb
);

insert into analysis 
  (id, analysis) values
  (1,  '{"category" : "news",    "results" : [1,   2,  3,  4,  5 , 6,  7,  8,  9,  10,  11,  12,  13,  14, null, null]}'),
  (2,  '{"category" : "news",    "results" : [11, 12, 13, 14, 15, 16, 17, 18, 19,  20,  21,  22,  23,  24, null,   26]}'),
  (3,  '{"category" : "news",    "results" : [31, 32, 33, 34, 35, 36, 37, 38, 39,  40,  41,  42,  43,  44,   45,   46]}'),
  (4,  '{"category" : "sport",   "results" : [51, 52, 53, 54, 55, 56, 57, 58, 59,  60,  61,  62,  63,  64,   65,   66]}'),
  (5,  '{"category" : "sport",   "results" : [71, 72, 73, 74, 75, 76, 77, 78, 79,  80,  81,  82,  83,  84,   85,   86]}'),
  (6,  '{"category" : "weather", "results" : [91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104,  105,  106]}');

如您所见,analysisJSONB字段始终包含2个属性category和results.结果属性将始终包含一个大小为16的固定长度数组.我已经使用了各种函数,jsonb_array_elements但我正在尝试做的是以下内容: -

1. 按分析分组 - >'类别'
2. 每个数组元素的平均值

当我想是返回按类别(即分组的3行的声明news,sport和weather)和含平均16个固定长度的数组.更复杂的是,如果null数组中有s,那么我们应该忽略它们(即我们不是简单地按行数求和和求平均值).结果应如下所示: -

 category  | analysis_average
-----------+--------------------------------------------------------------------------------------------------------------
 "news"    | [14.33, 15.33, 16.33, 17.33, 18.33, 19.33, 20.33, 21.33, 22.33, 23.33, 24.33, 25.33, 26.33, 27.33,  45,  36]
 "sport"   | [61,       62,    63,    64,    65,    66,    67,    68,    69,    70,    71,    72,    73,    74,  75,  76]
 "weather" | [91,       92,    93,    94,    95,    96,    97,    98,    99,    00,   101,   102,   103,   104, 105, 106]

注意:注意第1行中最后2个数组中的45和36,它表示忽略nullss.

我曾考虑创建一个视图,将数组分解为16列,即

create view analysis_view as
select a.*,
(a.analysis->'results'->>0)::int as result0,
(a.analysis->'results'->>1)::int as result1
/* ... etc for all 16 array entries .. */
from analysis a;

这对我来说似乎非常不优雅,并且首先消除了使用数组的优点,但可能会使用这种方法一起破解某些东西.

任何指针或提示将非常感谢!

此外,性能非常重要,因此性能越高越好!

Answer 1

这适用于任何数组长度

select category, array_agg(average order by subscript) as average
from (
    select
        a.analysis->>'category' category,
        subscript,
        avg(v)::numeric(5,2) as average
    from
        analysis a,
        lateral unnest(
            array(select jsonb_array_elements_text(analysis->'results')::int)
        ) with ordinality s(v,subscript)
    group by 1, 2
) s
group by category
;
 category |                                                 average                                                  
----------+----------------------------------------------------------------------------------------------------------
 news     | {14.33,15.33,16.33,17.33,18.33,19.33,20.33,21.33,22.33,23.33,24.33,25.33,26.33,27.33,45.00,36.00}
 sport    | {61.00,62.00,63.00,64.00,65.00,66.00,67.00,68.00,69.00,70.00,71.00,72.00,73.00,74.00,75.00,76.00}
 weather  | {91.00,92.00,93.00,94.00,95.00,96.00,97.00,98.00,99.00,100.00,101.00,102.00,103.00,104.00,105.00,106.00}

表函数 - 具有序数

侧