Обсуждение: BUG #15242: JSON functions not recognizing JSON
The following bug has been logged on the website:
Bug reference: 15242
Logged by: David
Email address: david@daily-harvest.com
PostgreSQL version: 9.6.6
Operating system: Mac / DBeaver
Description:
I get this error: SQL Error [22023]: ERROR: cannot deconstruct an array as
an object
when running the statement below because the JSON_EACH function doesn't
recognize the JSON. If I remove the json_each function the query runs fine
and executes JSON_ARRAY_LENGTH on the same variable, even though both
functions take json.
WITH sample_text AS
(
SELECT TEXT '[{"id":11,"name":"Chocolate +
Blueberry","sku":"11-CHOBLU"},{"id":11,"name":"Chocolate +
Blueberry","sku":"11-CHOBLU"}]' AS txt
)
SELECT json_array_length(txt::json), json_each(txt::json) FROM sample_text
On Thursday, June 14, 2018, PG Bug reporting form <noreply@postgresql.org> wrote:
The following bug has been logged on the website:
Bug reference: 15242
Logged by: David
Email address: david@daily-harvest.com
PostgreSQL version: 9.6.6
Operating system: Mac / DBeaver
Description:
I get this error: SQL Error [22023]: ERROR: cannot deconstruct an array as
an object
when running the statement below because the JSON_EACH function doesn't
recognize the JSON. If I remove the json_each function the query runs fine
and executes JSON_ARRAY_LENGTH on the same variable, even though both
functions take json.
WITH sample_text AS
(
SELECT TEXT '[{"id":11,"name":"Chocolate +
Blueberry","sku":"11-CHOBLU"},{"id":11,"name":"Chocolate +
Blueberry","sku":"11-CHOBLU"}]' AS txt
)
SELECT json_array_length(txt::json), json_each(txt::json) FROM sample_text
This is not a bug, nor is the behavior wrong.
json_each requires that the json being passed to it is a json object, not a json array. The docs and the error message say as much.
As json_each outputs two columns, one with the key and the other with the value, and since arrays don't have keys, it follows that json_each would be unable to operate on them.
David J.
>>>>> "PG" == PG Bug reporting form <noreply@postgresql.org> writes:
PG> I get this error: SQL Error [22023]: ERROR: cannot deconstruct an
PG> array as an object
PG> when running the statement below because the JSON_EACH function
PG> doesn't recognize the JSON.
It recognizes the json just fine, and so it can tell that it's an array
rather than the expected object. You were looking for
json_array_elements rather than (or prior to) json_each if you want to
enumerate the objects:
-- to get one row per object:
select json_array_length(txt::json), a.value
from sample_text, json_array_elements(txt::json) as a;
-- to get one row per object key:
select json_array_length(txt::json), a.value, a.ord, e.key, e.value
from sample_text,
json_array_elements(txt::json) with ordinality as a(value,ord),
json_each(a.value) as e;
--
Andrew (irc:RhodiumToad)