显示Flask-SQLAlchemy生成的SQL

Question

I want to get the SQL issued by Flask-SQLAlchemy queries. In Django, I can print the query attribute to get SQL. How can I get something similar in Flask?

# django
>>> queryset = MyModel.objects.all()
>>> print queryset.query
SELECT "myapp_mymodel"."id", ... FROM "myapp_mymodel"

Answer 1

Flask-SQLAlchemy records debugging information about all queries during a request. You can get the information with get_debug_queries() . Flask-Debugtoolbar , for example, uses this to offer a debug panel with query timing information on each page render.

get_debug_queries() returns a list of queries in the order they were performed.

>>> from my_app import User
>>> from flask_sqlalchemy import get_debug_queries
>>> User.query.filter_by(display_name='davidism').all()
>>> info = get_debug_queries()[0]
>>> print(info.statement, info.parameters, info.duration, sep='\n')
SELECT "user".id AS user_id, se_user.id AS se_user_id, se_user.display_name AS se_user_display_name, se_user.profile_image AS se_user_profile_image, se_user.profile_link AS se_user_profile_link, se_user.reputation AS se_user_reputation, "user".superuser AS user_superuser \nFROM se_user JOIN "user" ON se_user.id = "user".id \nWHERE se_user.display_name = %(display_name_1)s
{'display_name_1': 'davidism'}
0.0016849040985107422

Queries are recorded if SQLALCHEMY_RECORD_QUERIES is set to True . This should be disabled when not needed for performance reasons.

---

Just calling str(query) does not show exactly what is sent to the database, as the final render is up to the lower-level database driver. SQLAlchemy has only the parameterized string and unescaped parameters. See the SQLAlchemy docs for a very detailed explanation of why. Usually it's good enough, but it's good to be aware that it's not the final query.

Answer 2

I have found answer. I just invoke str and then get the sql.

>>> str(User.query.filter_by(role_id=user_role))
'SELECT users.id AS users_id, users.username AS users_username, users.role_id AS
 users_role_id \nFROM users \nWHERE users.role_id = :role_id_1'

Answer 3

To print the generated SQL for all the queries, set the configuration SQLALCHEMY_ECHO=True .

app.config['SQLALCHEMY_ECHO'] = True

http://flask-sqlalchemy.pocoo.org/2.3/config/