チェックオブジェクトキーは、次のようになりますjsonb配列を指定したオブジェクト

Question

のJSON配列で二回表示される場合：私は二回{ "type": "foo" }表示された場合はtrueを返すPostgreSQLの関数を作成したいと思います

[ 
    { "type": "foo", "desc": "example" }, 

    { "type": "foo", "desc": "second example" }, 

    { "type": "bar", "desc": "third example" } 
] 

を。

Answer 1

使用jsonb_array_elements()、例えば：

with data(js) as (
    select 
     '[ 
     { "type": "foo", "desc": "example" }, 
     { "type": "foo", "desc": "second example" }, 
     { "type": "bar", "desc": "third example" } 
     ]'::jsonb 
) 
select elem->>'type' as "type", count(elem->'type') 
from data, jsonb_array_elements(js) elem 
group by 1; 

type | count 
------+------- 
foo |  2 
bar |  1 
(2 rows)  

関数は次のようになります。

create or replace function check_duplicates(source jsonb, key text) 
returns boolean language sql as $$ 
    select max(count) > 1 
    from (
     select count(elem->key) 
     from jsonb_array_elements(source) elem 
     group by elem->key 
     ) s 
$$; 

使用法：

with data(js) as (
    select 
     '[ 
     { "type": "foo", "desc": "example" }, 
     { "type": "foo", "desc": "second example" }, 
     { "type": "bar", "desc": "third example" } 
     ]'::jsonb 
) 
select check_duplicates(js, 'type') 
from data; 

check_duplicates 
------------------ 
t 
(1 row) 

Answer 2

はここでそれを行う機能です。

CREATE OR REPLACE FUNCTION more_than_two_foos(s jsonb) RETURNS bool AS $$ 
DECLARE 
    c integer; 
BEGIN 
    SELECT count(*) 
    FROM (
     SELECT 1 
     FROM jsonb_array_elements(s) 
     WHERE value->>'type'='foo' 
     LIMIT 2 
    ) t 
    INTO c; 
    RETURN c>=2; 
END; 
$$ LANGUAGE plpgsql IMMUTABLE STRICT; 

そしてここではいくつかの例です：

$ SELECT more_than_two_foos('[ 
    { "type": "foo", "desc": "example" }, 
    { "type": "foo", "desc": "second example" }, 
    { "type": "bar", "desc": "third example" } 
]'); 
more_than_two_foos 
-------------------- 
t 
(1 row) 

$ SELECT more_than_two_foos('[ 
    { "type": "foo", "desc": "second example" }, 
    { "type": "bar", "desc": "third example" } 
]'); 
more_than_two_foos 
-------------------- 
f 
(1 row) 

アイデアそれはjsonb_array_elementsを使用してjsonb配列の要素を通過し、fooに等しいtypeを持つ要素を数えるということです。