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python-requestspostgrest

PostgREST returns no error with wrong JSON values (Python request)

I'm trying to make a client for postgREST (latest version with PostgreSQL 13)

When I tried to insert data, I felt on (what seems to me) a strange behavior: when I use json.dumps for an insert request, event if my value are wrong, I get a 201 code in response.

Working code
The field id is a primary key.

headers["Authorization"] = mytoken
myjson = {"id": "13", "name":"nameinserted"}
r = requests.post(url, json=myjson, headers=headers)

Returns a 201 code If I retry that code, I get a 409 (which is normal)

Not working code :
This one always returns me a 201 code, and never insert something in database (even with correct data). The difference is json.dumps(myjson) that I used by mistake.

headers["Authorization"] = mytoken
myjson = {"id": "13", "name":"nameinserted"}
myjson = json.dumps(myjson)
r = requests.post(url, json=myjson, headers=headers)

Why don't I get an error about data or malformed json?

Solution

  • In the first example you gave, the JSON encoded payload sent to PostgREST is:

    '{"id": "13", "name": "nameinserted"}'

    In the second example, after encoding it once again, the payload sent is:

    '"{\\"id\\": \\"13\\", \\"name\\": \\"nameinserted\\"}"'

    PostgREST parses the first payload as a JSON value; on the other hand, the second payload is parsed as a String value, equivalent to '"any_string"' for example. PostgREST is lenient with this type of payload and doesn't give an error but defaults it to an empty JSON array '[]', which is allowed even if the array is empty due to bulk insertion, and responds with a 201.