[英]SQLAlchemy: filtering by a key in a JSON column
SQLAlchemy 版本:1.2.10,PostgreSQL 版本:10 多岁。
我正在关注这里的文档示例
In [1]: import sqlalchemy as sa
In [2]: from nimble_core.backend.persistence.pg import PG_META_DATA
In [3]: data_table = sa.Table('data_table', PG_META_DATA,
...: sa.Column('id', sa.Integer, primary_key=True),
...: sa.Column('data', sa.JSON)
...: )
In [4]: data_table.create()
In [5]: with PG_ENGINE.connect() as conn:
...: conn.execute(
...: data_table.insert(),
...: data = {"key1": "value1", "key2": "value2"}
...: )
...:
在哪里:
In [10]: PG_ENGINE
Out[10]: Engine(postgresql://nimble:***@localhost:5432/nimble)
In [11]: PG_META_DATA
Out[11]: MetaData(bind=Engine(postgresql://nimble:***@localhost:5432/nimble))
In [12]: PG_META_DATA.sorted_tables
Out[12]:
[Table('data_table', MetaData(bind=Engine(postgresql://nimble:***@localhost:5432/nimble)), Column('id', Integer(), table=<data_table>, primary_key=True, nullable=False), Column('data', JSON(), table=<data_table>), schema=None)]
插入操作后,表只有一行:
In [14]: PG_ENGINE.execute(sa.select([data_table])).fetchall()
Out[14]: [(1, {u'key2': u'value2', u'key1': u'value1'})]
我试图做的下一件事是由下在我的JSON列中的特定键的值查询行,下面这个例子:
In [17]: PG_ENGINE.execute(
...: sa.select([data_table]).where(
...: data_table.c.data['key1'].astext == 'value1'
...: )
...: )
---------------------------------------------------------------------------
AttributeError Traceback (most recent call last)
<ipython-input-17-3c4db8afed3f> in <module>()
1 PG_ENGINE.execute(
2 sa.select([data_table]).where(
----> 3 data_table.c.data['key1'].astext == 'value1'
4 )
5 )
/Users/psih/Work/nimble-server/runtime/lib/python2.7/site-packages/sqlalchemy/sql/elements.pyc in __getattr__(self, key)
686 type(self).__name__,
687 type(self.comparator).__name__,
--> 688 key)
689 )
690
AttributeError: Neither 'BinaryExpression' object nor 'Comparator' object has an attribute 'astext'
显然, data_table.c.data['key1']
是( sqlalchemy.sql.elements.BinaryExpression
)没有属性astext
。 这是否意味着文档是错误的?
您正在使用sqlalchemy.types.JSON不具有astext
。 改用sqlalchemy.dialects.postgresql.JSON
import sqlalchemy as sa
from sqlalchemy.dialects import postgresql
data_table = sa.Table('data_table', PG_META_DATA,
sa.Column('id', sa.Integer, primary_key=True),
sa.Column('data', postgresql.JSON)
)
您可以在 sqlalchemy 过滤器中使用原始 sql
from sqlalchemy import text
db.session.query(DataTable).filter(text("data->['key1'] = 'value1'")
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