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SQLAlchemy中的日期时间筛选不起作用。

pythondatetimesqlalchemy
12

基本上，我需要构建一个函数，根据给定的日期过滤查询并返回新的查询结果。我对SQLAlchemy不熟悉，虽然我查找了类似的问题，但仍然遇到了相同的错误：

`Don't know how to literal-quote value datetime.datetime(2018, 1, 1, 8, 3, 1, 438278)`

这是我的代码：

def filter_dates(query_obj, datecols, start = None, end = None):
        if end is None:
            end = datetime.datetime.now()
        if start is None:
            start = end - datetime.timedelta(weeks=12)
        print("%s to %s" % (start, end))
        for datecol in datecols:
            print("Filtrando datas!")
            query_obj = query_obj.filter(datecol >= start)
            query_obj = query_obj.filter(datecol <= end)
            ReevTable.print_query(query_obj)
        return query_obj

datecols是一个orm.attributes对象。假设我有一个名为User的对象，其中有一个名为created_at的Datetime属性。这是预期的行为：

query = session.query(Company.name, Company.created_at, Company.number_of_employees, Company.email_bounce_rate)
query = filter_dates(query_obj=query, datecols = [Company.created_at, Company.email_events.created_at])
query.all()

期望输出是一张表格，其中包含在指定日期范围内创建的公司，并且跳出率应该仅在该指定日期范围内计算。这可能看起来很奇怪，但我不仅计算电子邮件，还计算其他类型的交互，因此我需要输入一个属性列表而不仅仅是单个属性。这就是为什么我需要使用一个方法来分隔这个筛选的原因。
我尝试过使用pandas datetime和timedelta、内置的python datetime模块以及简单的字符串与pd.to_datetime，但都没有成功。每次都会引发相同的错误。我的Company列是DateTime类型，所以我不知道还能做什么。
class Company(Base)
    created_at = Column(DateTime, nullable=False)

我完全不了解SQLAlchemy，我做错了什么吗？

完整的回溯：

`Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "reev-data-science/tables/reevtable.py", line 128, in import_data
    self.print_query(query_obj)
  File "reev-data-science/tables/reevtable.py", line 107, in print_query
    print(bcolors.OKBLUE + bcolors.BOLD + str(query_obj.statement.compile(compile_kwargs={"literal_binds":True})) + bcolors.ENDC)
  File "<string>", line 1, in <lambda>
  File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/sql/elements.py", line 442, in compile
    return self._compiler(dialect, bind=bind, **kw)
  File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/sql/elements.py", line 448, in _compiler
    return dialect.statement_compiler(dialect, self, **kw)
  File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/sql/compiler.py", line 453, in __init__
    Compiled.__init__(self, dialect, statement, **kwargs)
  File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/sql/compiler.py", line 219, in __init__
    self.string = self.process(self.statement, **compile_kwargs)
  File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/sql/compiler.py", line 245, in process
    return obj._compiler_dispatch(self, **kwargs)
  File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/sql/annotation.py", line 80, in _compiler_dispatch
    self, visitor, **kw)
  File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/sql/visitors.py", line 81, in _compiler_dispatch
    return meth(self, **kw)
  File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/sql/compiler.py", line 1815, in visit_select
    text, select, inner_columns, froms, byfrom, kwargs)
  File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/sql/compiler.py", line 1899, in _compose_select_body
    t = select._whereclause._compiler_dispatch(self, **kwargs)
  File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/sql/visitors.py", line 81, in _compiler_dispatch
    return meth(self, **kw)
  File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/sql/compiler.py", line 829, in visit_clauselist
    for c in clauselist.clauses)
  File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/sql/compiler.py", line 826, in <genexpr>
    s for s in
  File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/sql/compiler.py", line 829, in <genexpr>
    for c in clauselist.clauses)
  File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/sql/visitors.py", line 81, in _compiler_dispatch
    return meth(self, **kw)
  File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/sql/compiler.py", line 829, in visit_clauselist
    for c in clauselist.clauses)
  File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/sql/compiler.py", line 826, in <genexpr>
    s for s in
  File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/sql/compiler.py", line 829, in <genexpr>
    for c in clauselist.clauses)
  File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/sql/visitors.py", line 81, in _compiler_dispatch
    return meth(self, **kw)
  File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/sql/compiler.py", line 1080, in visit_binary
    return self._generate_generic_binary(binary, opstring, **kw)
  File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/sql/compiler.py", line 1113, in _generate_generic_binary
    self, eager_grouping=eager_grouping, **kw)
  File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/sql/visitors.py", line 81, in _compiler_dispatch
    return meth(self, **kw)
  File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/sql/compiler.py", line 1244, in visit_bindparam
    bindparam, within_columns_clause=True, **kwargs)
  File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/sql/compiler.py", line 1277, in render_literal_bindparam
    return self.render_literal_value(value, bindparam.type)
  File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/sql/compiler.py", line 1295, in render_literal_value
    "Don't know how to literal-quote value %r" % value)
NotImplementedError: Don't know how to literal-quote value datetime.datetime(2018, 1, 1, 9, 24, 46, 54634)`

打印查询(print_query()) 方法：
`def print_query(query_obj):
    print(bcolors.OKBLUE + bcolors.BOLD + str(query_obj.statement.compile(compile_kwargs={"literal_binds":True})) + bcolors.ENDC)`
1
请包含完整的回溯信息。我怀疑你的 ReevTable.print_query(query_obj) 是罪魁祸首，尽管你没有包含它的定义。 - Ilja Everilä
对不起，我没有意识到它可能与那个有关。我已经更新了帖子。 - Felipe Muniz
1
如果你检查 traceback，你会注意到打印查询语句是由于使用字面绑定而导致异常。这个与此非常相关并且值得一读。同时也请查看官方文档上的相关内容："上述方法有一个缺陷，即只支持基本类型（如 int 和 string）"。 - Ilja Everilä
你说得对！非常感谢。你能建议一种打印查询对象语句的方法，而不会丢失我输入的参数信息吗？因为如果我删除literal_binds，代码可以工作，但我看不到正在过滤的实际日期。 - Felipe Muniz
1
链接的问答和文档（实际上它们是相同的文本）都建议使用自定义的TypeDecorator来处理不支持渲染字面量的类型，并实现TypeDecorator.process_literal_param()。 - Ilja Everilä
2个回答
1

我遇到了与 DateTime 类型相同的问题。如果您想要使用仅带有 literal_binds: True 参数编译语句，并且查询中有复杂的字段（不是 int 或 string），则会出现此错误。

stmt.compile(dialect=postgresql.dialect(), compile_kwargs={"literal_binds": True})

使用TypeDecorator解决了这个问题。

解决方案：

from sqlalchemy import insert, create_engine, MetaData, Table, Column, DateTime, TypeDecorator
from sqlalchemy.dialects import postgresql
import psycopg2
from datetime import datetime

engine = create_engine('postgresql+psycopg2://postgres:password@127.0.0.1/postgres')
conn = engine.connect()

class MyDateTimeType(TypeDecorator):
    impl = DateTime

    def process_literal_param(self, value, dialect):
        return value.strftime("'%Y-%m-%d %H:%M:%S'")

meta = MetaData()
dates = Table('dates', meta, Column('created_at', MyDateTimeType(), nullable=False))

stmt = (
    insert(dates).
    values(created_at=datetime.now())
)

raw_sql = stmt.compile(dialect=postgresql.dialect(), compile_kwargs={"literal_binds": True})

conn.execute(raw_sql)
1

在你的筛选条件中将 datatime 对象转换为 str

def filter_dates(query_obj, datecols, start = None, end = None):
        if end is None:
            end = datetime.datetime.now()
        if start is None:
            start = end - datetime.timedelta(weeks=12)
        print("%s to %s" % (start, end))
        for datecol in datecols:
            print("Filtrando datas!")
            query_obj = query_obj.filter(datecol >= str(start))
            query_obj = query_obj.filter(datecol <= str(end))
            ReevTable.print_query(query_obj)
        return query_obj
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