[英]SQLAlchemy filter according to nested keys in JSONB
I have a JSONB field that sometimes has nested keys. 我有一个JSONB字段,有时有嵌套键。 Example: 例:
{"nested_field": {"another URL": "foo", "a simple text": "text"},
"first_metadata": "plain string",
"another_metadata": "foobar"}
If I do 如果我做
.filter(TestMetadata.metadata_item.has_key(nested_field))
I get this record. 我得到了这个记录。
How can I search for existence of the nested key? 如何搜索嵌套密钥的存在? ( "a simple text"
) ( "a simple text"
)
With SQLAlchemy the following should work for your test string: 使用SQLAlchemy,以下内容适用于您的测试字符串:
class TestMetadata(Base):
id = Column(Integer, primary_key=True)
name = Column(String)
metadata_item = Column(JSONB)
as per SQLAlchemy documentation of JSONB
(search for Path index operations example): 根据JSONB
SQLAlchemy文档 (搜索Path索引操作示例):
expr = TestMetadata.metadata_item[("nested_field", "a simple text")]
q = (session.query(TestMetadata.id, expr.label("deep_value"))
.filter(expr != None)
.all())
which should generate the SQL
below: 哪个应生成以下SQL
:
SELECT testmetadata.id AS testmetadata_id,
testmetadata.metadata_item #> %(metadata_item_1)s AS deep_value
FROM testmetadata
WHERE (testmetadata.metadata_item #> %(metadata_item_1)s) IS NOT NULL
-- @params: {'metadata_item_1': u'{nested_field, a simple text}'}
This query tests for existence of the nested field with the ?
此查询测试是否存在嵌套字段?
operator , after extracting the nested JSON object with the ->
operator : 运算符 ,在使用->
运算符提取嵌套的JSON对象之后:
SELECT EXISTS (
SELECT 1
FROM testmetadata
WHERE metadata_item->'nested_field' ? 'a simple text'
);
Note that a plain GIN index does not support this query. 请注意,普通GIN索引不支持此查询。 You would need an expression index on metadata_item->'nested_field'
to make this fast. 您需要在metadata_item->'nested_field'
上使用表达式索引才能使其快速。
CREATE INDEX testmetadata_special_idx ON testmetadata
USING gin ((metadata_item->'nested_field'));
There is an example in the manual for a similar case. 手册中有一个类似案例的例子。
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