如何在帶有 sqlalchemy 的 sqlite 中使用 regexp 函數？

Question

我想在“sqlalchemy”中使用正則表達式查詢以及在“python sqlite”中完成，代碼如下..

未完成的沙盒腳本是這樣的：

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())

我發現應該在每個線程上注冊 regexp 函數：

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

但我無法對我的腳本采用鏈接的解決方案 + 它已被棄用。

更新

我想查詢這個：

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 中。

Answer 1

我有答案..缺少一行的完整工作腳本是這樣的：

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我得到錯誤：

“sqlalchemy.exc.OperationalError :( OperationalError）沒有這樣的函數：regexp ..”

也許是因為這種變化：

指定基於文件的數據庫時，方言將使用NullPool作為連接源。 此池關閉並丟棄立即返回池的連接。 SQLite基於文件的連接具有極低的開銷，因此不需要池化 。 該方案還可以防止連接在不同的線程中再次使用，並且最適合SQLite的粗粒度文件鎖定。 在0.7版中更改：默認選擇NullPool for SQLite基於文件的數據庫。 以前的版本默認為所有SQLite數據庫選擇SingletonThreadPool。

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

解決方法是：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))

...

Answer 2

差不多10年后...

它在 SQLAlchemy 1.4 中更容易工作：

stmt = select(table.c.some_column).where(
    table.c.some_column.regexp_match('^(b|c)')
)

來源： https ://docs.sqlalchemy.org/en/14/core/sqlelement.html#sqlalchemy.sql.expression.ColumnElement.regexp_match