如何在sqlalchemy中使用sqlite中的regexp函数？

Question

我想在"sqlalchemy"中使用regexp查询以及在"python sqlite"中完成,代码如下.

未完成的沙盒脚本是这样的:

import os
import re
import sqlite3

#
# python sqlite
#

DB_PATH = __name__ + '.db'

try:
    os.remove(DB_PATH)
except:
    pass


def re_fn(expr, item):
    reg = re.compile(expr, re.I)
    return reg.search(item) is not None

conn = sqlite3.connect(':memory:')
conn = sqlite3.connect(DB_PATH)
conn.create_function("REGEXP", 2, re_fn)
cursor = conn.cursor()

cursor.execute(
    'CREATE TABLE t1 (id INTEGER PRIMARY KEY, c1 TEXT)'
)
cursor.executemany(
    #'INSERT INTO t1 (c1) VALUES (?)', [('aaa"test"',),('blah',)]
    'INSERT INTO t1 (c1) VALUES (?)', [
        ('dupa / 1st Part',), ('cycki / 2nd Part',), ('fiut / 3rd Part',)
    ]
)
cursor.execute(
    #'SELECT c1 FROM t1 WHERE c1 REGEXP ?',['2|3\w+part']
    'SELECT c1 FROM t1 WHERE c1 REGEXP ?',['\d\w+ part']
)
conn.commit()
data=cursor.fetchall()
print(data)



#
# sqlalchemy
#

import sqlalchemy as sa
import sqlalchemy.orm as orm
from sqlalchemy.ext.declarative import declarative_base

DSN = 'sqlite:///' + DB_PATH
engine = sa.create_engine(DSN, convert_unicode=True)
db = orm.scoped_session(orm.sessionmaker(autocommit=False,
                                         autoflush=False,
                                         bind=engine))

Base = declarative_base(bind=engine)
meta = Base.metadata

class T1(Base):
    __table__ = sa.Table('t1', meta, autoload=True)

print(db.query(T1).all())

我发现应该在每个线程上注册regexp函数:

http://permalink.gmane.org/gmane.comp.web.pylons.general/12742

但是我无法对我的脚本采用链接的解决方案+它已被弃用.

更新

我想查询一下:

cursor.execute(
    #'SELECT c1 FROM t1 WHERE c1 REGEXP ?',['2|3\w+part']
    'SELECT c1 FROM t1 WHERE c1 REGEXP ?',['\d\w+ part']
)

但在sqlalchemy.

Answer 1

我有答案..缺少一行的完整工作脚本是这样的:

import os
import re
import sqlite3

DB_PATH = __name__ + '.db'

try:
    os.remove(DB_PATH)
except:
    pass


def re_fn(expr, item):
    reg = re.compile(expr, re.I)
    return reg.search(item) is not None

conn = sqlite3.connect(':memory:')
conn = sqlite3.connect(DB_PATH)
conn.create_function("REGEXP", 2, re_fn)
cursor = conn.cursor()

cursor.execute(
    'CREATE TABLE t1 (id INTEGER PRIMARY KEY, c1 TEXT)'
)
cursor.executemany(
    #'INSERT INTO t1 (c1) VALUES (?)', [('aaa"test"',),('blah',)]
    'INSERT INTO t1 (c1) VALUES (?)', [
        ('dupa / 1st Part',), ('cycki / 2nd Part',), ('fiut / 3rd Part',)
    ]
)
SEARCH_TERM = '3rd part'
cursor.execute(
    #'SELECT c1 FROM t1 WHERE c1 REGEXP ?',['2|3\w+part']
    'SELECT c1 FROM t1 WHERE c1 REGEXP ?',[SEARCH_TERM]
)
conn.commit()
data=cursor.fetchall()
print(data)



#
# sqlalchemy
#

import sqlalchemy as sa
import sqlalchemy.orm as orm
from sqlalchemy.ext.declarative import declarative_base

DSN = 'sqlite:///' + DB_PATH

engine = sa.create_engine(DSN, convert_unicode=True)

conn = engine.connect()
conn.connection.create_function('regexp', 2, re_fn)

db = orm.scoped_session(orm.sessionmaker(autocommit=False,
                                         autoflush=False,
                                         bind=engine))

Base = declarative_base(bind=engine)
meta = Base.metadata

class T1(Base):
    __table__ = sa.Table('t1', meta, autoload=True)

print(db.query(T1.c1).filter(T1.c1.op('regexp')(SEARCH_TERM)).all())

以上工作在sqlalchemy = 0.6.3

在sqlalchemy = 0.7.8我得到错误:

"sqlalchemy.exc.OperationalError :( OperationalError)没有这样的函数:regexp .."

也许是因为这种变化:

指定基于文件的数据库时,方言将使用NullPool作为连接源.此池关闭并丢弃立即返回池的连接.SQLite基于文件的连接具有极低的开销,因此不需要池化.该方案还可以防止连接在不同的线程中再次使用,并且最适合SQLite的粗粒度文件锁定.在0.7版中更改:默认选择NullPool for SQLite基于文件的数据库.以前的版本默认为所有SQLite数据库选择SingletonThreadPool.

来自:http://docs.sqlalchemy.org/en/rel_0_7/dialects/sqlite.html?highlight=isolation_level#threading-pooling-behavior

解决方法是:在'begin'事件中添加regexp fn,如下所示:

...

conn = engine.connect()
@sa.event.listens_for(engine, "begin")
def do_begin(conn):
    conn.connection.create_function('regexp', 2, re_fn)

db = orm.scoped_session(orm.sessionmaker(autocommit=False,
                                         autoflush=False,
                                         bind=engine))

...