SQLAlchemy with PostgresSQL and Full Text Search

Question

我正在使用烧瓶，sqlalchemy和flask-sqlalchemy。我想用杜松子酒和to_tsvector在postgres中创建一个完整的测试搜索索引。目前，我正在尝试以下内容。我认为它与我想要表达的最接近，但不起作用。

from sqlalchemy.ext.declarative import declared_attr 
from sqlalchemy.schema import Index 
from sqlalchemy.sql.expression import func 

from app import db 


class Post(db.Model): 

    id = db.Column(db.Integer, primary_key=True) 
    added = db.Column(db.DateTime, nullable=False) 
    pub_date = db.Column(db.DateTime, nullable=True) 
    content = db.Column(db.Text) 

    @declared_attr 
    def __table_args__(cls): 
     return (Index('idx_content', func.to_tsvector("english", "content"), postgresql_using="gin"),) 

这引发以下错误......

Traceback (most recent call last): 
    File "./manage.py", line 5, in <module> 
    from app import app, db 
    File "/vagrant/app/__init__.py", line 36, in <module> 
    from pep.models import * 
    File "/vagrant/pep/models.py", line 8, in <module> 
    class Post(db.Model): 
    File "/home/vagrant/.virtualenvs/pep/local/lib/python2.7/site-packages/flask_sqlalchemy.py", line 477, in __init__ 
    DeclarativeMeta.__init__(self, name, bases, d) 
    File "/home/vagrant/.virtualenvs/pep/local/lib/python2.7/site-packages/sqlalchemy/ext/declarative/api.py", line 48, in __init__ 
    _as_declarative(cls, classname, cls.__dict__) 
    File "/home/vagrant/.virtualenvs/pep/local/lib/python2.7/site-packages/sqlalchemy/ext/declarative/base.py", line 222, in _as_declarative 
    **table_kw) 
    File "/home/vagrant/.virtualenvs/pep/local/lib/python2.7/site-packages/sqlalchemy/schema.py", line 326, in __new__ 
    table._init(name, metadata, *args, **kw) 
    File "/home/vagrant/.virtualenvs/pep/local/lib/python2.7/site-packages/sqlalchemy/schema.py", line 393, in _init 
    self._init_items(*args) 
    File "/home/vagrant/.virtualenvs/pep/local/lib/python2.7/site-packages/sqlalchemy/schema.py", line 63, in _init_items 
    item._set_parent_with_dispatch(self) 
    File "/home/vagrant/.virtualenvs/pep/local/lib/python2.7/site-packages/sqlalchemy/events.py", line 235, in _set_parent_with_dispatch 
    self._set_parent(parent) 
    File "/home/vagrant/.virtualenvs/pep/local/lib/python2.7/site-packages/sqlalchemy/schema.py", line 2321, in _set_parent 
    ColumnCollectionMixin._set_parent(self, table) 
    File "/home/vagrant/.virtualenvs/pep/local/lib/python2.7/site-packages/sqlalchemy/schema.py", line 1978, in _set_parent 
    self.columns.add(col) 
    File "/home/vagrant/.virtualenvs/pep/local/lib/python2.7/site-packages/sqlalchemy/sql/expression.py", line 2391, in add 
    self[column.key] = column 
    File "/home/vagrant/.virtualenvs/pep/local/lib/python2.7/site-packages/sqlalchemy/sql/expression.py", line 2211, in __getattr__ 
    key) 
AttributeError: Neither 'Function' object nor 'Comparator' object has an attribute 'key' 

我也试过

return (Index('idx_content', "content", postgresql_using="gin"),) 

但是，它并没有Postgres的工作（9.1至少，因为这是我运行的）期望to_tsvector被调用。这一行创建SQL;

CREATE INDEX content_index ON post USING gin (content) 

而不是我想要的;

CREATE INDEX content_index ON post USING gin(to_tsvector('english', content)) 

我打开了一张票，因为我认为这可能是一个错误/限制。 http://www.sqlalchemy.org/trac/ticket/2605

Answer 1

现在我已经添加了以下几行手动执行它，但是我更愿意'正确的'SQLAlchemy方法（如果有的话）。

create_index = DDL("CREATE INDEX idx_content ON pep USING gin(to_tsvector('english', content));") 
event.listen(Pep.__table__, 'after_create', create_index.execute_if(dialect='postgresql')) 

关于SQLAlchemy错误跟踪器有一些有趣的讨论。看起来这是对当前索引定义的限制。基本上，我的要求是允许索引是表达式而不是列名，但目前不支持。此故障单正在跟踪此功能请求：http://www.sqlalchemy.org/trac/ticket/695。但是，这正在等待开发人员继续并开展工作（并且已经有一段时间了）。

Answer 2

所以在SQLAlchemy的0.9及以上工作的：

class Content(Base,): 
    __tablename__ = 'content' 

    id = sa.Column(sa.Integer, primary_key=True) 

    description = sa.Column(sa.UnicodeText, nullable=False, server_default='') 
    @declared_attr 
    def __table_args__(cls): 
     return (sa.Index('idx_content', 
        sa.sql.func.to_tsvector("english", cls.description), 
        postgresql_using="gin"),) 

值得注意的是，从第一个例子不同的是直接引用列名，而不是在引号所提供的列名，为不工作。