Python SQLAlchemy:打印实际查询
我真的希望能够为我的应用程序打印出有效的SQL,包括值,而不是绑定参数,但在SQLAlchemy中如何做到这一点并不明显(通过设计,我相当确定)Python SQLAlchemy:打印实际查询,python,sqlalchemy,Python,Sqlalchemy,我真的希望能够为我的应用程序打印出有效的SQL,包括值,而不是绑定参数,但在SQLAlchemy中如何做到这一点并不明显(通过设计,我相当确定) 有人用一般方法解决了这个问题吗?这在Python2和Python3中工作,比以前更简洁,但需要SA>=1.0 from sqlalchemy.engine.default import DefaultDialect from sqlalchemy.sql.sqltypes import String, DateTime, NullType # pyt
有人用一般方法解决了这个问题吗?这在Python2和Python3中工作,比以前更简洁,但需要SA>=1.0
from sqlalchemy.engine.default import DefaultDialect
from sqlalchemy.sql.sqltypes import String, DateTime, NullType
# python2/3 compatible.
PY3 = str is not bytes
text = str if PY3 else unicode
int_type = int if PY3 else (int, long)
str_type = str if PY3 else (str, unicode)
class StringLiteral(String):
"""Teach SA how to literalize various things."""
def literal_processor(self, dialect):
super_processor = super(StringLiteral, self).literal_processor(dialect)
def process(value):
if isinstance(value, int_type):
return text(value)
if not isinstance(value, str_type):
value = text(value)
result = super_processor(value)
if isinstance(result, bytes):
result = result.decode(dialect.encoding)
return result
return process
class LiteralDialect(DefaultDialect):
colspecs = {
# prevent various encoding explosions
String: StringLiteral,
# teach SA about how to literalize a datetime
DateTime: StringLiteral,
# don't format py2 long integers to NULL
NullType: StringLiteral,
}
def literalquery(statement):
"""NOTE: This is entirely insecure. DO NOT execute the resulting strings."""
import sqlalchemy.orm
if isinstance(statement, sqlalchemy.orm.Query):
statement = statement.statement
return statement.compile(
dialect=LiteralDialect(),
compile_kwargs={'literal_binds': True},
).string
演示:
给出以下输出:(在Python2.7和3.4中测试)
这段代码基于@bukzor的brilliant。我刚刚为
datetime添加了自定义渲染。datetime
输入到Oracle的TO_DATE()
请随时更新代码以适合您的数据库:
import decimal
import datetime
def printquery(statement, bind=None):
"""
print a query, with values filled in
for debugging purposes *only*
for security, you should always separate queries from their values
please also note that this function is quite slow
"""
import sqlalchemy.orm
if isinstance(statement, sqlalchemy.orm.Query):
if bind is None:
bind = statement.session.get_bind(
statement._mapper_zero_or_none()
)
statement = statement.statement
elif bind is None:
bind = statement.bind
dialect = bind.dialect
compiler = statement._compiler(dialect)
class LiteralCompiler(compiler.__class__):
def visit_bindparam(
self, bindparam, within_columns_clause=False,
literal_binds=False, **kwargs
):
return super(LiteralCompiler, self).render_literal_bindparam(
bindparam, within_columns_clause=within_columns_clause,
literal_binds=literal_binds, **kwargs
)
def render_literal_value(self, value, type_):
"""Render the value of a bind parameter as a quoted literal.
This is used for statement sections that do not accept bind paramters
on the target driver/database.
This should be implemented by subclasses using the quoting services
of the DBAPI.
"""
if isinstance(value, basestring):
value = value.replace("'", "''")
return "'%s'" % value
elif value is None:
return "NULL"
elif isinstance(value, (float, int, long)):
return repr(value)
elif isinstance(value, decimal.Decimal):
return str(value)
elif isinstance(value, datetime.datetime):
return "TO_DATE('%s','YYYY-MM-DD HH24:MI:SS')" % value.strftime("%Y-%m-%d %H:%M:%S")
else:
raise NotImplementedError(
"Don't know how to literal-quote value %r" % value)
compiler = LiteralCompiler(dialect, statement)
print compiler.process(statement)
在绝大多数情况下,SQLAlchemy语句或查询的“字符串化”非常简单:
print(str(statement))
这既适用于ORM查询
,也适用于任何select()
或其他语句
注意:以下详细答案保存在网站上
要将语句编译为特定方言或引擎,如果语句本身尚未绑定到某个方言或引擎,则可以将其传递到:
或没有发动机:
from sqlalchemy.dialects import postgresql
print(statement.compile(dialect=postgresql.dialect()))
当给定ORMQuery
对象时,为了获得compile()
方法,我们只需要首先访问访问器:
statement = query.statement
print(statement.compile(someengine))
关于绑定参数要“内联”到最终字符串的原始规定,这里的挑战是SQLAlchemy通常不负责此任务,因为这是由Python DBAPI适当处理的,更不用说绕过绑定参数可能是现代web应用程序中最广泛利用的安全漏洞。SQLAlchemy在某些情况下(例如发出DDL的情况)执行这种字符串化的能力有限。为了访问此功能,可以使用传递给compile\u kwargs
的“literal\u binds”标志:
from sqlalchemy.sql import table, column, select
t = table('t', column('x'))
s = select([t]).where(t.c.x == 5)
print(s.compile(compile_kwargs={"literal_binds": True}))
上述方法需要注意的是,它只支持基本的
类型,例如int和string,而且如果abindparam
如果不直接使用预设值,它将无法
也要把它严格化
要支持不支持的类型的内联文字呈现,请实现
目标类型的TypeDecorator
,其中包括
TypeDecorator.process\u literal\u param
方法:
from sqlalchemy import TypeDecorator, Integer
class MyFancyType(TypeDecorator):
impl = Integer
def process_literal_param(self, value, dialect):
return "my_fancy_formatting(%s)" % value
from sqlalchemy import Table, Column, MetaData
tab = Table('mytable', MetaData(), Column('x', MyFancyType()))
print(
tab.select().where(tab.c.x > 5).compile(
compile_kwargs={"literal_binds": True})
)
产生如下产出:
SELECT mytable.x
FROM mytable
WHERE mytable.x > my_fancy_formatting(5)
因此,在@zzzeek对@bukzor代码的评论的基础上,我提出了一个简单的“可打印”查询:
我个人很难阅读没有缩进的代码,所以我使用了
sqlparse
来重新修改SQL。它可以与pip install sqlparse一起安装。我想指出的是,上面给出的解决方案并不“只适用于”非平凡的查询。我遇到的一个问题是更复杂的类型,例如导致问题的pgsql数组。我确实找到了一个解决方案,对我来说,它甚至可以用于pgsql阵列:
借用自:
链接的代码似乎基于SQLAlchemy的旧版本。您将得到一个错误,指出属性_mapper_zero_或_none不存在。这里有一个更新的版本,可以与更新的版本一起使用,您只需将_mapper_zero_或_none替换为bind即可。此外,它还支持pgsql阵列:
# adapted from:
# https://gist.github.com/gsakkis/4572159
from datetime import date, timedelta
from datetime import datetime
from sqlalchemy.orm import Query
try:
basestring
except NameError:
basestring = str
def render_query(statement, dialect=None):
"""
Generate an SQL expression string with bound parameters rendered inline
for the given SQLAlchemy statement.
WARNING: This method of escaping is insecure, incomplete, and for debugging
purposes only. Executing SQL statements with inline-rendered user values is
extremely insecure.
Based on http://stackoverflow.com/questions/5631078/sqlalchemy-print-the-actual-query
"""
if isinstance(statement, Query):
if dialect is None:
dialect = statement.session.bind.dialect
statement = statement.statement
elif dialect is None:
dialect = statement.bind.dialect
class LiteralCompiler(dialect.statement_compiler):
def visit_bindparam(self, bindparam, within_columns_clause=False,
literal_binds=False, **kwargs):
return self.render_literal_value(bindparam.value, bindparam.type)
def render_array_value(self, val, item_type):
if isinstance(val, list):
return "{%s}" % ",".join([self.render_array_value(x, item_type) for x in val])
return self.render_literal_value(val, item_type)
def render_literal_value(self, value, type_):
if isinstance(value, long):
return str(value)
elif isinstance(value, (basestring, date, datetime, timedelta)):
return "'%s'" % str(value).replace("'", "''")
elif isinstance(value, list):
return "'{%s}'" % (",".join([self.render_array_value(x, type_.item_type) for x in value]))
return super(LiteralCompiler, self).render_literal_value(value, type_)
return LiteralCompiler(dialect, statement).process(statement)
测试了两个级别的嵌套数组。我们可以使用此方法。从:
结果:
SELECT * FROM users WHERE users.name BETWEEN 'm' AND 'z'
来自文档的警告:
切勿将此技术用于从不受信任的服务器接收的字符串内容
输入,例如来自web表单或其他用户输入应用程序的输入。
SQLAlchemy将Python值强制转换为直接SQL字符串的功能
值对于不受信任的输入不安全,并且不会验证
正在传递的数据类型。在以下情况下始终使用绑定参数:
对关系数据库以编程方式调用非DDL SQL语句
数据库
考虑到您想要的只有在调试时才有意义,您可以使用
echo=True
启动SQLAlchemy来记录所有SQL查询。例如:
engine = create_engine(
"mysql://scott:tiger@hostname/dbname",
encoding="latin1",
echo=True,
)
也可以针对单个请求进行修改:
echo=False
–如果True
,引擎将把所有语句及其参数列表的repr()
记录到引擎记录器,该记录器默认为sys.stdout
。Engine
的echo
属性可以随时修改以打开和关闭日志记录。如果设置为字符串“debug”
,结果行也将打印到标准输出。该标志最终控制Python记录器;有关如何直接配置日志记录的信息,请参阅
资料来源:
如果与烧瓶一起使用,您只需设置
app.config["SQLALCHEMY_ECHO"] = True
获得相同的行为。只是一个带有ORM查询和pygments的简单彩色示例
import sqlparse
from pygments import highlight
from pygments.formatters.terminal import TerminalFormatter
from pygments.lexers import SqlLexer
from sqlalchemy import create_engine
from sqlalchemy.orm import Query
engine = create_engine("sqlite+pysqlite:///db.sqlite", echo=True, future=True)
def format_sql(query: Query):
compiled = query.statement.compile(
engine, compile_kwargs={"literal_binds": True})
parsed = sqlparse.format(str(compiled), reindent=True, keyword_case='upper')
print(highlight(parsed, SqlLexer(), TerminalFormatter()))
或者没有sqlparse的版本(没有sqlparse,输出中的新行更少)
我没有,但是您可以通过使用SQLAlchemy的
SQLAlchemy.engine
log来构建一个不那么脆弱的解决方案。它记录查询和绑定参数,您只需用现成构造的SQL查询字符串上的值替换绑定占位符。@Simon:使用记录器有两个问题:1)它只在语句执行时打印2)我仍然需要进行字符串替换,除非在这种情况下,我不知道绑定模板字符串的确切位置,我必须以某种方式从查询文本中解析它,使解决方案更加脆弱。新的URL似乎是为@zzzeek的FAQ提供的。我不明白为什么SA人员认为如此简单的操作如此困难是合理的。谢谢!render_literal_值对我来说效果很好。我唯一的更改是:return“%s”%value
而不是float,int,long部分中的return repr(value)
,因为Python将long输出为22L
,而不是22
,如果任何bindparam字符串值不能用ascii表示,则此配方(以及原始配方)将引发UnicodeDecodeError。我贴了一张
from sqlalchemy.sql import text
from sqlalchemy.dialects import postgresql
stmt = text("SELECT * FROM users WHERE users.name BETWEEN :x AND :y")
stmt = stmt.bindparams(x="m", y="z")
print(stmt.compile(dialect=postgresql.dialect(),compile_kwargs={"literal_binds": True}))
SELECT * FROM users WHERE users.name BETWEEN 'm' AND 'z'
engine = create_engine(
"mysql://scott:tiger@hostname/dbname",
encoding="latin1",
echo=True,
)
app.config["SQLALCHEMY_ECHO"] = True
import sqlparse
from pygments import highlight
from pygments.formatters.terminal import TerminalFormatter
from pygments.lexers import SqlLexer
from sqlalchemy import create_engine
from sqlalchemy.orm import Query
engine = create_engine("sqlite+pysqlite:///db.sqlite", echo=True, future=True)
def format_sql(query: Query):
compiled = query.statement.compile(
engine, compile_kwargs={"literal_binds": True})
parsed = sqlparse.format(str(compiled), reindent=True, keyword_case='upper')
print(highlight(parsed, SqlLexer(), TerminalFormatter()))
def format_sql(query: Query):
compiled = query.statement.compile(
engine, compile_kwargs={"literal_binds": True})
print(highlight(str(compiled), SqlLexer(), TerminalFormatter()))