Question

我有一个表mapping_transform，其中包含JSONB列content_json，其中包含

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

我想将新的JSON条目（"rule_names": [ "some name" ]）添加到与src = up和dest = down匹配的JSON对象中，这将导致在

{
    "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。我试过像

这样的东西

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

但由于results是未知列，因此无法执行。我还需要在分配给jsonb_set之前将content_json的结果与content_json的其余部分合并，否则它会覆盖整个内容。

如何根据过滤条件更新特定的深层嵌套JSON对象？如果我有一个定义良好的路径，我想要更新我的对象，那么事情就会容易得多。但由于目标对象位于JSON数组中且具有任意位置，因此查找和更新它会更加困难。

Answer 1

如果您熟悉JavaScript，您将乐意安装和使用JavaScript procedural language plv8.此扩展允许您原生修改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：ready to install Windows binaries.

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);

Answer 2

我在这里建立路径：concat('{mapping,',(ord::int-1),'}')::text[]其余的相同。请注意我加入text = text（因为我不知道你的PK是什么 - 不推荐）。将值保留为更新，右侧原始：

vao=# with num as (select content_json,val,ord from mapping_transform, json_array_elements(content_json->'mapping') with ordinality as o (val,ord) where val->>'src' = 'up')
select
  jsonb_pretty(
    jsonb_set(t.content_json::jsonb,concat('{mapping,',(ord::int-1),'}')::text[],((t.content_json->'mapping'->(ord::int-1))::jsonb||'{"rule_names":["some name"]}')::jsonb)
  )
, jsonb_pretty(t.content_json::jsonb)
from mapping_transform t
join num on num.content_json::text = t.content_json::text
/* of course join should be on PK, not text representation*/
;
        jsonb_pretty         |        jsonb_pretty
-----------------------------+----------------------------
 {                          +| {                         +
     "meta": {              +|     "meta": {             +
         "a": true          +|         "a": true         +
     },                     +|     },                    +
     "mapping": [           +|     "mapping": [          +
         "a",               +|         "a",              +
         "c",               +|         "c",              +
         {                  +|         {                 +
             "a": 0,        +|             "a": 0,       +
             "src": "up",   +|             "src": "up",  +
             "dest": "down",+|             "dest": "down"+
             "rule_names": [+|         },                +
                 "some name"+|         "b"               +
             ]              +|     ]                     +
         },                 +| }
         "b"                +|
     ]                      +|
 }                           |
 {                          +| {                         +
     "meta": {              +|     "meta": {             +
         "a": true          +|         "a": true         +
     },                     +|     },                    +
     "mapping": [           +|     "mapping": [          +
         "a",               +|         "a",              +
         {                  +|         {                 +
             "a": 0,        +|             "a": 0,       +
             "src": "up",   +|             "src": "up",  +
             "dest": "down",+|             "dest": "down"+
             "rule_names": [+|         },                +
                 "some name"+|         "b"               +
             ]              +|     ]                     +
         },                 +| }
         "b"                +|
     ]                      +|
 }                           |
(2 rows)

和构建：

vao=# create table mapping_transform(content_json jsonb);
CREATE TABLE
vao=#  insert into mapping_transform select '{
 "meta": {
  "a": true
 },
 "mapping": ["a",{
   "src": "up",
   "dest": "down",
   "a": 0
  },
  "b"
 ]
}';
INSERT 0 1
vao=#  insert into mapping_transform select '{
 "meta": {
  "a": true
 },
 "mapping": ["a","c",{
   "src": "up",
   "dest": "down",
   "a": 0
  },
  "b"
 ]
}';
INSERT 0 1

如何根据Postgres中的过滤条件更新深层嵌套的JSON对象？

2 个答案: