postgresql-用于构建json的查询
正在运行:PostgreSQL 9.6.2 我将数据以键/值对的形式存储在一个表中。“键”实际上是一个json对象的路径,每个对象都是一个属性。例如,如果键是“cogs”、“props1”、“value”,那么json对象如下:postgresql-用于构建json的查询,json,postgresql,jsonb,Json,Postgresql,Jsonb,正在运行:PostgreSQL 9.6.2 我将数据以键/值对的形式存储在一个表中。“键”实际上是一个json对象的路径,每个对象都是一个属性。例如,如果键是“cogs”、“props1”、“value”,那么json对象如下: { "cogs":{ "props1": { "value": 100 } } } 如果可能的话,我希望通过SQL查询以某种方式重建json对象。以下是测试数据集: drop table if exists test
{
"cogs":{
"props1": {
"value": 100
}
}
}
如果可能的话,我希望通过SQL查询以某种方式重建json对象。以下是测试数据集:
drop table if exists test_table;
CREATE TABLE test_table
(
id serial,
file_id integer NOT NULL,
key character varying[],
value character varying,
status character varying
)
WITH (
OIDS = FALSE
)
TABLESPACE pg_default;
insert into test_table (file_id, key, value, status)
values (1, '{"cogs","description"}', 'some awesome cog', 'approved');
insert into test_table (file_id, key, value, status)
values (1, '{"cogs","display"}', 'Giant Cog', null);
insert into test_table (file_id, key, value, status)
values (1, '{"cogs","props1","value"}', '100', 'not verified');
insert into test_table (file_id, key, value, status)
values (1, '{"cogs","props1","id"}', 26, 'approved');
insert into test_table (file_id, key, value, status)
values (1, '{"cogs","props1","dimensions"}', '{"200", "300"}', null);
insert into test_table (file_id, key, value, status)
values (1, '{"cogs","props2","value"}', '200', 'not verified');
insert into test_table (file_id, key, value, status)
values (1, '{"cogs","props2","id"}', 27, 'approved');
insert into test_table (file_id, key, value, status)
values (1, '{"cogs","props2","dimensions"}', '{"700", "800"}', null);
insert into test_table (file_id, key, value, status)
values (1, '{"widgets","description"}', 'some awesome widget', 'approved');
insert into test_table (file_id, key, value, status)
values (1, '{"widgets","display"}', 'Giant Widget', null);
insert into test_table (file_id, key, value, status)
values (1, '{"widgets","props1","value"}', '100', 'not verified');
insert into test_table (file_id, key, value, status)
values (1, '{"widgets","props1","id"}', 28, 'approved');
insert into test_table (file_id, key, value, status)
values (1, '{"widgets","props1","dimensions"}', '{"200", "300"}', null);
insert into test_table (file_id, key, value, status)
values (1, '{"widgets","props2","value"}', '200', 'not verified');
insert into test_table (file_id, key, value, status)
values (1, '{"widgets","props2","id"}', 29, 'approved');
insert into test_table (file_id, key, value, status)
values (1, '{"widgets","props2","dimensions"}', '{"900", "1000"}', null);
我要查找的输出格式如下:
{
"cogs": {
"description": "some awesome cog",
"display": "Giant Cog",
"props1": {
"value": 100,
"id": 26,
"dimensions": [200, 300]
},
"props2": {
"value": 200,
"id": 27,
"dimensions": [700, 800]
}
},
"widgets": {
"description": "some awesome widget",
"display": "Giant Widget",
"props1": {
"value": 100,
"id": 28,
"dimensions": [200, 300]
},
"props2": {
"value": 200,
"id": 29,
"dimensions": [900, 1000]
}
}
}
我面临的一些问题:
动态解决方案需要一些工作 首先,我们需要一个函数将文本数组和值转换为jsonb对象
create or replace function keys_to_object(keys text[], val text)
returns jsonb language plpgsql as $$
declare
i int;
rslt jsonb = to_jsonb(val);
begin
for i in select generate_subscripts(keys, 1, true) loop
rslt := jsonb_build_object(keys[i], rslt);
end loop;
return rslt;
end $$;
select keys_to_object(array['key', 'subkey', 'subsub'], 'value');
keys_to_object
------------------------------------------
{"key": {"subkey": {"subsub": "value"}}}
(1 row)
接下来是另一个合并jsonb对象的函数(请参阅)
我们做到了:
select jsonb_pretty(jsonb_merge_agg(keys_to_object(key, translate(value, '{}"', '[]'))))
from test_table;
jsonb_pretty
----------------------------------------------
{ +
"cogs": { +
"props1": { +
"id": "26", +
"value": "100", +
"dimensions": "[200, 300]" +
}, +
"props2": { +
"id": "27", +
"value": "200", +
"dimensions": "[700, 800]" +
}, +
"display": "Giant Cog", +
"description": "some awesome cog" +
}, +
"widgets": { +
"props1": { +
"id": "28", +
"value": "100", +
"dimensions": "[200, 300]" +
}, +
"props2": { +
"id": "29", +
"value": "200", +
"dimensions": "[900, 1000]" +
}, +
"display": "Giant Widget", +
"description": "some awesome widget"+
} +
}
(1 row)
拜托,今晚我以你的名义喝了一杯凉的!令人惊讶的是,这是有效的!显然,我还有很多需要学习的地方:)在聚合期间是否可以保留行顺序?我一直在阅读自定义聚合,但仍然有点困惑,因此我在这里回答。不幸的是没有。根据JSON定义,名称/值对的集合是无序的。要存储有序的值列表,应该使用JSON数组。参见。Postgres JSONB不保证json集合中的任何顺序。但是,您可以尝试使用json而不是JSONB。在整个脚本中将
jsonb
替换为json
,并删除jsonb_pretty()
(此函数没有json等效函数)。对象的顺序应该保持在表中,但这是json类型的未记录功能。进行了这些更改,可以确认它确实保留了顺序!太好了。读了很多,JSON类型的性能似乎比JSONB差。。。然而,在我的情况下,这是不明显的。谢谢你的帮助!
create aggregate jsonb_merge_agg(jsonb)
(
sfunc = jsonb_merge,
stype = jsonb
);
select jsonb_pretty(jsonb_merge_agg(keys_to_object(key, translate(value, '{}"', '[]'))))
from test_table;
jsonb_pretty
----------------------------------------------
{ +
"cogs": { +
"props1": { +
"id": "26", +
"value": "100", +
"dimensions": "[200, 300]" +
}, +
"props2": { +
"id": "27", +
"value": "200", +
"dimensions": "[700, 800]" +
}, +
"display": "Giant Cog", +
"description": "some awesome cog" +
}, +
"widgets": { +
"props1": { +
"id": "28", +
"value": "100", +
"dimensions": "[200, 300]" +
}, +
"props2": { +
"id": "29", +
"value": "200", +
"dimensions": "[900, 1000]" +
}, +
"display": "Giant Widget", +
"description": "some awesome widget"+
} +
}
(1 row)