我使用PostgreSQL 9.5和Rails5。我想查询jsonb
下面显示的包含JSON对象数组的列,以返回所有包含{"kind":"person"}
并执行计数的JSON数组元素。我使用
的SQL显示在json数据下方。运行查询只会返回一个空数组。
这是我的jsonb
数据:
'[
{"kind":"person", "filter_term":"56","selected_attr":"customer"},
{"kind":"email", "filter_term":"marketer","selected_attr":"job_title"}
]'
我想要其中一个sql查询返回:
data
----------------------------------------------------------------------
'{"kind":"person", "filter_term":"56","selected_attr":"customer"}'
(1 row)
和另一个查询以返回数组,以便我可以在我的应用程序中对其进行调用,还可以遍历它以创建表单:
data
----------------------------------------------------------------------
'[{"kind":"person", "filter_term":"56","selected_attr":"customer"}]'
(1 row)
我试过这个SQL查询:
"SELECT * FROM \"segments\" WHERE (payload @> '[{\"kind\":\"person\"}]')"
我也尝试过以下查询:
"SELECT payload FROM segments WHERE payload @> '[{\"kind\":\"person\"}]'::jsonb;"
这是第三个查询:
"SELECT * FROM segments s WHERE s.payload->'\"#{a}\"' @> '[{\"kind\":\"person\"}]';"
该模型:
class Segment < ApplicationRecord
store_accessor :payload,:kind, :filter_term, :selected_model_name, :selected_attr, :limit, :selected_operator
end
迁移:
create_table "segments", force: :cascade do |t|
t.jsonb "payload", default: "[]", null: false
t.index ["payload"], name: "index_segments_on_payload", using: :gin
end
假设此表定义:
CREATE TABLE segments (segments_id serial PRIMARY KEY, payload jsonb);
使用这样的JSON值:
INSERT INTO segments (payload)
VALUES ('[
{
"kind": "person",
"limit": "1",
"filter_term": "56",
"selected_attr": "customer",
"selected_operator": "less_than"
},
{
"kind": "email",
"filter_term": "marketer",
"selected_attr": "job_title",
"selected_operator": "equals"
}
]'
);
"kind":"person"
JSON{"kind":"person"}
数组元素(不是嵌套的JSON对象),并计数数组元素以及表行(每行可能有多个匹配的数组元素)。要获取在column中包含合格值的行数:jsonb
segments
SELECT count(*)
FROM segments s
WHERE s.payload @> '[{"kind":"person"}]';
要获取所有合格的JSON数组元素(本身就是JSON对象)-加上元素的总数(可能同时大于上述总数):
SELECT j.*
FROM segments s
JOIN LATERAL jsonb_array_elements(s.payload) j(elem) ON j.elem @> '{"kind":"person"}'
WHERE s.payload @> '[{"kind":"person"}]';
返回值:
元素 ------------------------------------------------- ----------- {“ kind”:“ person”,“ limit”:“ 1”,“ filter_term”:“ 56”,...}
一次全部获取:
SELECT j.*, count(*) OVER () AS ct_elem, s.ct_rows
FROM (
SELECT payload, count(*) OVER () AS ct_rows
FROM segments
WHERE payload @> '[{"kind":"person"}]'
) s
JOIN LATERAL jsonb_array_elements(s.payload) j(elem) ON j.elem @> '{"kind":"person"}';
返回(对于具有更多条目的表):
元素| ct_elem | ct_rows -------------------------- + --------- + --------- {“种类“:”人“,...} | 4 | 3 {“种类”:“人”,...} | 4 | 3 ...
但我认为您真的想要这样:
SELECT a.*
, sum(ct_elem_row) OVER () AS ct_elem_total
, count(*) OVER () AS ct_rows
FROM segments s
JOIN LATERAL (
SELECT json_agg(j.elem) AS filtered_payload, count(*) AS ct_elem_row
FROM jsonb_array_elements(s.payload) j(elem)
WHERE j.elem @> '{"kind":"person"}'
) a ON ct_elem_row > 0
WHERE s.payload @> '[{"kind":"person"}]';
返回(对于具有更多条目的表):
filter_payload | ct_elem_row | ct_elem_total | ct_rows ------------------------------------------------- ---- + ------------- + --------------- + --------- [{“种类”: “人”,...}] | 1 | 4 | 3 [{“ kind”:“ person”,...}] | 1 | 4 | 3 [{“种类”:“人”,...},{“种类”:“人”,...}] | 2 | 4 | 3
这将标识匹配的行,然后选择匹配的数组元素,并仅使用那些元素为每行构建一个数组。加计数。
为了获得最佳性能,您将具有如下的jsonb_path_ops
GIN索引:
CREATE INDEX segments_path_ops_gin_idx ON segments
USING gin (payload jsonb_path_ops);
(但是,可以使用更通用的索引来服务更多不同的查询是更好的选择。)
有关:
术语
我们正在处理一个包含JSON数组的JSON对象,该对象保存为Postgresjsonb
数据类型-简称为“ JSON数组”,而不是“ JSON数组”。
本文收集自互联网,转载请注明来源。
如有侵权,请联系 [email protected] 删除。
我来说两句