如何基于Postgres中的过滤条件更新深层嵌套的JSON对象? [英] How to update deeply nested JSON object based on filter criteria in Postgres?

问题描述

我有一个表mapping_transform，其中的JSONB列content_json包含类似内容

I have a table mapping_transform with a JSONB column content_json containing something like

{
    "meta": {...},
    "mapping": [
        ...,
        {
            "src": "up",
            "dest": "down",
            ...
        },
        ...
    ]
}

我想向与src = up和dest = down匹配的JSON对象添加一个新的JSON条目("rule_names": [ "some name" ])，这将导致

I want to add a new JSON entry ("rule_names": [ "some name" ]) to the JSON object matching src = up and dest = down, which would result in

{
    "meta": {...},
    "mapping": [
        ...,
        {
            "src": "up",
            "dest": "down",
            ...,
            "rule_names": [ "some name" ]
        },
        ...
    ]
}

以下查询返回满足过滤条件的 JSON对象:

The following query returns the JSON object that meets the filter requirements:

WITH elems AS (SELECT json_array_elements(content_json->'mapping') from mapping_transform)
SELECT * FROM elems WHERE json_array_elements->>'src' = 'up' and json_array_elements->>'dest' = 'down';

-- Alternative

SELECT mt_entry
FROM mapping_transform,
LATERAL jsonb_array_elements(content_json::jsonb->'mapping') mt_entry
WHERE mt_entry->>'src' = 'up' and mt_entry->>'dest' = 'down';

我现在的问题是我不知道如何将新条目添加到特定对象.我尝试过类似的

My problem now is that I do not know how to add the new entry to the specific object. I tried something like

WITH elems AS (SELECT json_array_elements(content_json->'mapping') from mapping_transform),
     results SELECT * FROM elems WHERE json_array_elements->>'src' = 'up' and json_array_elements->>'dest' = 'down'
UPDATE mapping_transform
SET content_json = jsonb_set(results, '{"rule_names"}', '["some name"]'); -- this does obviously not work

，但不作为results执行，是未知列.在分配给content_json之前，我还确实需要将jsonb_set的结果与content_json的其余部分合并，因为否则它将覆盖整个内容.

but that does not execute as results is an unknown column. I also do need to merge the result of the jsonb_set with the rest of the content_json before assigning to content_json, because otherwise it would override the whole content.

如何根据过滤条件更新特定的深层嵌套JSON对象? 如果我有一个明确的路径来确定要更新的对象，那么事情会容易得多.但是由于目标对象位于JSON数组中并且具有任意位置，因此查找和更新目标要困难得多.

How can I update specific deeply nested JSON objects based on filter criteria? If I had a well defined path as to where my object is that I want to update, things would be much easier. But as the target object lies within a JSON array and has an arbitrary position, finding and updating it is much more difficult.

推荐答案

如果您熟悉JavaScript，将很乐意安装和使用 JavaScript过程语言plv8.此扩展允许您本地修改json值，例如:

If you are familiar with JavaScript you'll be happy to install and use JavaScript procedural language plv8. This extension allows you to modify json values natively, example:

create extension if not exists plv8;

create or replace function update_mapping_v8(data json)
returns json language plv8 as $$
    var len = data['mapping'].length;
    for (var i = 0; i < len; i++) {
        var o = data['mapping'][i];
        if (o.src == 'up' && o.dest == 'down') {
            o.rule_names = 'some name'
        }
    }
    return data;
$$;

update mapping_transform
set content_json = update_mapping_v8(content_json);

对于MS Windows用户:

For MS Windows users: ready to install Windows binaries.

plpgsql替代解决方案使用jsonb类型:

A plpgsql alternative solution uses jsonb type:

create or replace function update_mapping_plpgsql(data jsonb)
returns json language plpgsql as $$
declare
    r record;
begin
    for r in
        select value, ordinality- 1 as pos
        from jsonb_array_elements(data->'mapping') with ordinality
        where value->>'src' = 'up' and value->>'dest' = 'down'
    loop
        data = jsonb_set(
            data,
            array['mapping', r.pos::text],
            r.value || '{"rule_names": "some name"}'
            );
    end loop;
    return data;
end $$;

update mapping_transform
set content_json = update_mapping_plpgsql(content_json::jsonb);

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