Question

我试图创建一个功能索引（PostgreSQL函数lower（））。使用Alembic创建表时出现此错误：

sqlalchemy.exc.ProgrammingError: (ProgrammingError) column "lower" does not exist
 'CREATE INDEX ix_cities_name ON cities (lower)' {}

以下是代码：

from flask import Flask
from flask.ext.sqlalchemy import SQLAlchemy

app = Flask(__name__)
db = SQLAlchemy(app)

class City(db.Model):
    __tablename__ = 'cities'

    name = db.Column(db.String(100), nullable=False)

db.Index('ix_cities_name', db.func.lower(db.metadata.tables['cities'].c.name))

Answer 1

你可以这样做：

from sqlalchemy import func

db.Index('ix_cities_name', func.lower(City.name))

参考：

Functional indexes are supported as well, typically by using the
:data:`.func` construct in conjunction with table-bound
:class:`.Column` objects::

    Index("some_index", func.lower(sometable.c.name))

另外，感谢您提出这个问题，我知道如何创建索引！

Answer 2

不幸的是，alembic无法为功能索引生成正确的修订版（我希望）。您的迁移应该如下所示：

op.execute("CREATE INDEX ix_cities_name ON cities (LOWER(name))")

Flask-SQLAlchemy：创建功能索引

2 个答案: