如何基于Postgres中的过滤条件更新深层嵌套的JSON对象？

Question

我有一个mapping_transform带有JSONB列的表，content_json其中包含类似

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

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

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

以下查询返回符合过滤器要求 的JSON对象 ：

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。我尝试了类似的东西

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

但这不会像results未知列那样执行。在分配给之前，我还确实需要将的结果jsonb_set与其余的合并，因为否则会覆盖整个内容。content_json``content_json

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数组内并且具有
任意位置 ，因此查找和更新目标要困难得多。

Answer 1

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：

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：准备安装Windows二进制文件。

一个plpgsql替代解决方案使用jsonb类型：

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);