Postgres将JSONB单元扁平化为视图中的行 [英] Postgres flatten JSONB cell into row in view

问题描述

我有一个简单的postgres表:

I have a simple postgres table:

    Column    │         Type         │ Modifiers
──────────────┼──────────────────────┼──────────────────────
 id           │ integer              │ not null default
 data         │ jsonb                │

这是data的简化数据结构:

{
  "id": 3,
  "date": "2019-01-01",
  "well_report_table":
    [
      {"element": "methane",
      "yield": 6,
      "price": 2.10
      },
      {"element": "pentane",
      "yield": 6,
      "price": 2.10
      },
      {"element": "butane",
      "yield": 6,
      "price": 3.50
      }
    ],
  "cost_report_table":
    [
      {"item": "fuel",
      "charge": 6.30
      },
      {"item": "lease",
      "charge": 200
      }
    ]
}

我想在带有以下各列的视图中将其展平:

I'd like to flatten this in a view with the following columns:

id | date | well_report_table_methane_yield | well_report_table_methane_price | well_report_table_pentane_yield | well_report_table_pentane_price | well_report_table_butane_yield | well_report_table_butane_price |cost_report_table_fuel_charge | cost_report_table_lease_charge

我数组中的对象具有一个标识符，我想将其附加到数组对象名称中，然后遍历该对象中的其他键，并在 中创建列.

The objects in my arrays have an identifier that I would like to append to the array object name and then iterate through the other keys in the object and make columns out of .

这个问题使我接近: Postgres:展平聚合来自JSONB字段的键/值对?

This question gets me close: Postgres: Flatten aggregated key/value pairs from a JSONB field?

我不确定是否可以在plpgsql之类的工具中实现此功能，因此，如果我只需要使用脚本语言(如ruby/python)生成视图文本，然后再基于该脚本创建视图，则可以那个.

I'm not entirely sure this is possible in something like plpgsql, so if I just need to generate the view text in a scripting language like ruby/python and then create a view off of that, I'm a ok with that.

理想情况下，我可以使用jsonb_array_elements和jsonb_each之类的东西来避免中间表(我目前的所有尝试都需要中间视图)，但是我还没有发现这种魔术组合. /p>

Ideally I'll be able to use something like jsonb_array_elements and jsonb_each in order to avoid intermediate tables (all of my current attempts have required intermediate views), but I haven't found that magic combination yet.

推荐答案

这不是关于展平JSON数组的普遍问题，因为在数组中隐藏了特定的逻辑.您可以在此函数中实现逻辑:

This is not a general question about flattening JSON arrays, because there is a specific logic hidden in the arrays. You can implement the logic in this function:

create or replace function flat_array(data jsonb, title text, item text)
returns jsonb language sql immutable as $$
    select jsonb_object_agg(format('%s_%s_%s', title, elem->>item, key), value)
    from jsonb_array_elements(data->title) as arr(elem)
    cross join jsonb_each(elem)
    where key <> item
$$;

查询:

select 
    jsonb_build_object('id', data->'id', 'date', data->'date') ||
    flat_array(data, 'well_report_table', 'element') ||
    flat_array(data, 'cost_report_table', 'item')
from my_table

提供对象:

{
    "id": 3,
    "date": "2019-01-01",
    "cost_report_table_fuel_charge": 6.30,
    "cost_report_table_lease_charge": 200,
    "well_report_table_butane_price": 3.50,
    "well_report_table_butane_yield": 6,
    "well_report_table_methane_price": 2.10,
    "well_report_table_methane_yield": 6,
    "well_report_table_pentane_price": 2.10,
    "well_report_table_pentane_yield": 6
}

可以通过从JSONB字段中平铺的聚合键/值对转换为表格视图吗?

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