Question

我最近考虑将我们的产品数据库从mongo迁移到postgres。来自mongoDb，我习惯于＆＃34;放松＆＃34;对象和数组。

假设您有以下对象：

{
  "styleGroupId": "2",
  "brand": "MOP",
  "colorVariants": [
    {
        "color": "red",
        "colorCode": "222",
        "sizeVariants": [
           {"gtin": "444",
           "size": "M"},
           {"gtin": "555",
           "size": "L"}
       ]
    },
    {
        "color": "blue",
        "colorCode": "111",
        "sizeVariants": [
           {"gtin": "66",
           "size": "M"},
           {"gtin": "77",
           "size": "L"}
       ]
    }
    ]
}

如果你想展平它，在mongo中使用以下内容：

db.test.aggregate([
{
    $unwind: "$colorVariants"
},
{
    $unwind: "$colorVariants.sizeVariants"
}
])

将产生如下对象：

{
    "_id" : ObjectId("5a7dc59dafc86d25964b873c"),
    "styleGroupId" : "2",
    "brand" : "MOP",
    "colorVariants" : {
        "color" : "red",
        "colorCode" : "222",
        "sizeVariants" : {
            "gtin" : "444",
            "size" : "M"
        }
    }
}

我花了几个小时寻找＆＃34; mongo在postgres＆＃34;但几乎找不到令人满意的答案。在postgres中查询JSONB数据的很多资源几乎都没有触及嵌套数组。希望这篇文章能帮助其他可怜的灵魂寻找从mongoDb到postgres的迁移。

Answer 1

功能：

create or replace function jsonb_unwind(target jsonb, path text[])
returns jsonb language plpgsql as $$
begin
    if jsonb_typeof(target #> path) = 'array' then
        return jsonb_set(target, path, target #> path -> 0);
    else
        return target;
    end if;
end $$;

使用示例：

select 
    jsonb_unwind(
        jsonb_unwind(json_data, '{colorVariants}'), 
        '{colorVariants, sizeVariants}')
from my_table;

Test it in rextester.

Answer 2

在这篇文章中可以隐含地找到答案：How to query nested arrays in a postgres json column?

修改

与此回答配对use - to remove a key from a JSONB 从9.6
开始，有一种更简单的方法可以让你更接近mongo放松

您需要在查询的FROM子句中声明每个数组级别

从输出中排除每个嵌套对象，使其不会多次出现

可选连接对象和子对象

将对象与共享键连接时，只保留||运算符右侧对象的键

-

SELECT data::jsonb - 'colorVariants' || colorVariants.* - 'sizeVariants' || sizeVariants.* FROM test, jsonb_array_elements(data -> 'colorVariants') colorVariants, jsonb_array_elements(colorVariants -> 'sizeVariants') sizeVariants;

结果就是

?column? ------------------------------------------------------------------------------------------------------- {"gtin": "11", "size": "M", "brand": "MOP", "color": "red", "colorCode": "222", "styleGroupId": "1"} {"gtin": "22", "size": "L", "brand": "MOP", "color": "red", "colorCode": "222", "styleGroupId": "1"} {"gtin": "33", "size": "M", "brand": "MOP", "color": "blue", "colorCode": "111", "styleGroupId": "1"} {"gtin": "44", "size": "L", "brand": "MOP", "color": "blue", "colorCode": "111", "styleGroupId": "1"} {"gtin": "444", "size": "M", "brand": "MOP", "color": "red", "colorCode": "222", "styleGroupId": "2"} {"gtin": "555", "size": "L", "brand": "MOP", "color": "red", "colorCode": "222", "styleGroupId": "2"} {"gtin": "66", "size": "M", "brand": "MOP", "color": "blue", "colorCode": "111", "styleGroupId": "2"} {"gtin": "77", "size": "L", "brand": "MOP", "color": "blue", "colorCode": "111", "styleGroupId": "2"}

旧帖子

您必须在查询的FROM子句中声明每个数组级别

您必须专门列出每个级别的属性。如果你只说明例如colorVariants嵌套数组也将被返回

因此，在特定情况下，解决方案将是：

SELECT data->'brand' as brand, data->'styleGroupId' as styleGroupId, colorVariants->'color' as color, colorVariants->'colorCode' as colorCode, sizeVariants->'gtin' as GTIN, sizeVariants->'size' as size FROM test, jsonb_array_elements(data->'colorVariants') colorVariants, jsonb_array_elements(colorVariants->'sizeVariants') sizeVariants

将导致

brand | stylegroupid | color | colorcode | gtin | size -------+--------------+--------+-----------+-------+------ "MOP" | "1" | "red" | "222" | "11" | "M" "MOP" | "1" | "red" | "222" | "22" | "L" "MOP" | "1" | "blue" | "111" | "33" | "M" "MOP" | "1" | "blue" | "111" | "44" | "L" "MOP" | "2" | "red" | "222" | "444" | "M" "MOP" | "2" | "red" | "222" | "555" | "L" "MOP" | "2" | "blue" | "111" | "66" | "M" "MOP" | "2" | "blue" | "111" | "77" | "L"

我怎样才能实现mongo＆＃34;放松＆＃34;在postgres JSONB？（展平嵌套数组）

2 个答案:

我怎样才能实现mongo＆＃34;放松＆＃34;在postgres JSONB？ （展平嵌套数组）

2 个答案:

我怎样才能实现mongo＆＃34;放松＆＃34;在postgres JSONB？（展平嵌套数组）