无法在 Postgres 中查询整数数组

Question

已将列类型从 HSTORE 迁移到 JSONB，并且正在使用此 sn-p 代码...

from sqlalchemy.dialects.postgresql import ARRAY, JSONB

if employment_type:
        base = base.filter(Candidate.bio["employment_type"].cast(ARRAY).contains(employment_type))  

我收到了这个错误...

127.0.0.1 - - [28/Mar/2016 12:25:13] "GET /candidate_filter/?employment_type_3=true HTTP/1.1" 500 -
Traceback (most recent call last):
  File "/Library/Python/2.7/site-packages/flask/app.py", line 1836, in __call__
    return self.wsgi_app(environ, start_response)
  File "/Library/Python/2.7/site-packages/flask/app.py", line 1820, in wsgi_app
    response = self.make_response(self.handle_exception(e))
  File "/Library/Python/2.7/site-packages/flask/app.py", line 1403, in handle_exception
    reraise(exc_type, exc_value, tb)
  File "/Library/Python/2.7/site-packages/flask/app.py", line 1817, in wsgi_app
    response = self.full_dispatch_request()
  File "/Library/Python/2.7/site-packages/flask/app.py", line 1477, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/Library/Python/2.7/site-packages/flask/app.py", line 1381, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "/Library/Python/2.7/site-packages/flask/app.py", line 1475, in full_dispatch_request
    rv = self.dispatch_request()
  File "/Library/Python/2.7/site-packages/flask/app.py", line 1461, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "/Users/surajkapoor/Desktop/lhv-talenttracker/app/views.py", line 660, in investor_filter
    base = base.filter(Candidate.bio["employment_type"].cast(ARRAY).contains(employment_type))
  File "/Library/Python/2.7/site-packages/sqlalchemy/dialects/postgresql/json.py", line 93, in cast
    return self.astext.cast(type_)
  File "/Library/Python/2.7/site-packages/sqlalchemy/dialects/postgresql/json.py", line 95, in cast
    return sql.cast(self, type_)
  File "<string>", line 2, in cast

  File "/Library/Python/2.7/site-packages/sqlalchemy/sql/elements.py", line 2314, in __init__
    self.type = type_api.to_instance(type_)
  File "/Library/Python/2.7/site-packages/sqlalchemy/sql/type_api.py", line 1142, in to_instance
    return typeobj(*arg, **kw)
TypeError: __init__() takes at least 2 arguments (1 given)

Candidate.bio["employment_type"] 是一个整数数组，我只是想查询其中包含特定整数的所有行。

此外，当调用 Integer 时，.cast() 可以在同一列上完美运行...

if internship:
    base = base.filter(Candidate.bio["internship"].cast(Integer) == 1)  

Answer 1

SqlAlchemy 可能难以构造 where 子句，因为它无法确定 bio->'employment_type' 是什么类型。

如果从String 对象调用contains 方法，它将生成LIKE 子句，但对于JSONB 或ARRAY，则需要生成@> 运算符。

要为 SqlAlchemy 提供必要的提示，请在任何地方使用显式强制转换，即将查询编写为

from sqlalchemy import cast

if employment_type:
    casted_field = Candidate.bio['employment_type'].cast(JSONB)
    casted_values = cast(employment_type, JSONB)
    stmt = base.filter(casted_field.contains(casted_values))

Answer 2

在我的示例中，我有一个名为 bio 的 JSONB 列，其中包含以下数据：

{"employment_type": [1, 2, 3]}

编辑：转换为JSONB 有效：

>>> from sqlalchemy.dialects.postgresql import JSONB
>>> employment_type = 2

>>> query = (
...     session.query(Candidate)
...     .filter(Candidate.bio['employment_type'].cast(JSONB).contains(employment_type)))

>>> query.one().bio
{"employment_type": [1, 2, 3]}

原答案：

我无法让.contains 处理Candidate.bio['employment_type']，但我们可以执行与以下 SQL 等效的操作：

SELECT * FROM candidate WHERE candidate.bio @> '{"employment_type": [2]}';

像这样：

>>> employment_type = 2
>>> test = {'employment_type': [employment_type]}

>>> query = (
...     session.query(Candidate)
...     .filter(Candidate.bio.contains(test)))

>>> query.one().bio
{"employment_type": [1, 2, 3]}