在我的应用程序中，我有一个Job类，如下所示/概述。此作业类的实例代表特定的作业运行。作业可以有多个检查点，每个检查点可以有多个命令。
Job
- JobName
- [JobCheckpoint]
- StartTime
- EndTime
- Status
- ...
JobCheckpoint
- JobCheckpointName
- [JobCommand]
- StartTime
- EndTime
- Status
- ...
JobCommand
- JobCommandName
- [Command]
- StartTime
- EndTime
- Status
- ...
在任何一天，大约有10万个不同的作业在运行。作业信息保留在文件系统中。我想在Python中设计一个用于查询这些作业对象的用户界面。例如，用户应该能够查询
为解决这个问题，我正在考虑在用户界面中提供以下方法。
get_jobs(Filter)
我不确定如何在Python中设计此Filter类
这里的铅非常感谢。
答案 0 :(得分：3)
这些是部分主观的问题。但是，我将尽我所能，并根据所提出的问题中的可用信息回答其中的一些问题。
Filter类的外观如何？
例如，这可能取决于存储机制。它是作为一堆Python对象存储在内存中，还是首先从SQL数据库或NoSQL数据库中取出。
如果它是从SQL数据库中获取的，则可以利用SQL的过滤机制。毕竟是一种（结构化的）查询语言。
在这种情况下，您的Filter类就像是将字段值转换为一堆SQL运算符/条件的转换器。
如果它是一堆没有某种数据库机制可用于查询数据的Python对象，那么您可能需要考虑自己的查询/过滤器方法。
Filter类可能正在使用Condition类和Operator类。也许您有一个Operator类作为抽象类，并且有“胶合”操作符将条件粘合在一起（AND / OR）。还有另一种用于将域对象的属性与值进行比较的运算符。
对于后者，即使您没有为其设计“过滤器语言”，也可以从此处为Flask-Restless指定的API查询格式中获得启发：https://flask-restless.readthedocs.io/en/stable/searchformat.html#query-format
当然，如果您要设计一个查询界面，例如Flask-Restless的REST API作为一种REST API，可以为您提供有关如何解决查询的灵感。
返回的域对象列表正确还是应该返回字典列表？
返回域对象列表的优点是能够使用继承。那至少是一种可能的优势。
某些课程的简要草图：
from abc import ABCMeta, abstractmethod
from typing import List
class DomainObjectOperatorGlue(metaclass=ABCMeta):
@abstractmethod
def operate(self, haystack: List['DomainObject'], criteria:
List['DomainObject']) -> List['DomainObject']:
pass
class DomainObjectFieldGlueOperator(metaclass=ABCMeta):
@abstractmethod
def operate(self, conditions: List[bool]) -> bool:
pass
class DomainObjectFieldGlueOperatorAnd(DomainObjectFieldGlueOperator):
def operate(self, conditions: List[bool]) -> bool:
# If all conditions are True then return True here,
# otherwise return False.
# (...)
pass
class DomainObjectFieldGlueOperatorOr(DomainObjectFieldGlueOperator):
def operate(self, conditions: List[bool]) -> bool:
# If only one (or more) of the conditions are True then return True
# otherwise, if none are True, return False.
# (...)
pass
class DomainObjectOperatorAnd(DomainObjectOperatorGlue):
def __init__(self):
pass
def operate(self, haystack: 'JobsCollection', criteria:
List['DomainObject']) -> List['DomainObject']:
"""
Returns list of haystackelements or empty list.
Includes haystackelement if all (search) 'criteria' elements
(DomainObjects) are met for haystackelement (DomainObject).
"""
result = []
for haystackelement in haystack.jobs:
# AND operator wants all criteria to be True for haystackelement (Job)
# to be included in returned search results.
criteria_all_true_for_haystackelement = True
for criterium in criteria:
if haystackelement.excludes(criterium):
criteria_all_true_for_haystackelement = False
break
if criteria_all_true_for_haystackelement:
result.append(haystackelement)
return result
class DomainObjectOperatorOr(DomainObjectOperatorGlue):
def __init__(self):
pass
def operate(self, haystack: List['DomainObject'], criteria: List['DomainObject']) -> List['DomainObject']:
"""
Returns list of haystackelements or empty list.
Includes haystackelement if all (search) 'criteria' elements (DomainObjects) are met for haystackelement (DomainObject).
"""
result = []
for haystackelement in haystack:
# OR operator wants at least ONE criterium to be True for haystackelement
# to be included in returned search results.
at_least_one_criterium_true_for_haystackelement = False
for criterium in criteria:
if haystackelement.matches(criterium):
at_least_one_criterium_true_for_haystackelement = True
break
if at_least_one_criterium_true_for_haystackelement:
result.append(haystackelement)
return result
class DomainObjectFilter(metaclass=ABCMeta):
def __init__(self, criteria: List['DomainObject'], criteria_glue:
DomainObjectOperatorGlue):
self.criteria = criteria
self.criteria_glue = criteria_glue
@abstractmethod
def apply(self, haystack: 'JobsCollection') -> List['DomainObject']:
"""
Applies filter to given 'haystack' (list of jobs with sub-objects in there);
returns filtered list of DomainObjects or empty list if none found
according to criteria (and criteria glue).
"""
return self.criteria_glue.operate(haystack, self.criteria)
class DomainObject(metaclass=ABCMeta):
def __init__(self):
pass
@abstractmethod
def matches(self, domain_object: 'DomainObject') -> bool:
""" Returns True if this DomainObject matches specified DomainObject,
False otherwise.
"""
pass
def excludes(self, domain_object: 'DomainObject') -> bool:
"""
Convenience method; the inverse of includes-method.
"""
return not self.matches(domain_object)
class Job(DomainObject):
def __init__(self, name, start, end, status, job_checkpoints:
List['JobCheckpoint']):
self.name = name
self.start = start
self.end = end
self.status = status
self.job_checkpoints = job_checkpoints
def matches(self, domain_object: 'DomainObject', field_glue:
DomainObjectFieldGlueOperator) -> bool:
"""
Returns True if this DomainObject includes specified DomainObject,
False otherwise.
"""
if domain_object is Job:
# See if specified fields in search criteria (domain_object/Job) matches this job.
# Determine here which fields user did not leave empty,
# and guess for sensible search criteria.
# Return True if it's a match, False otherwise.
condition_results = []
if domain_object.name != None:
condition_results.append(domain_object.name in self.name)
if domain_object.start != None or domain_object.end != None:
if domain_object.start == None:
# ...Use broadest start time for criteria here...
# time_range_condition = ...
condition_results.append(time_range_condition)
elif domain_object.end == None:
# ...Use broadest end time for criteria here...
# time_range_condition = ...
condition_results.append(time_range_condition)
else:
# Both start and end time specified; use specified time range.
# time_range_condition = ...
condition_results.append(time_range_condition)
# Then evaluate condition_results;
# e.g. return True if all condition_results are True here,
# false otherwise depending on implementation of field_glue class:
return field_glue.operate(condition_results)
elif domain_object is JobCheckpoint:
# Determine here which fields user did not leave empty,
# and guess for sensible search criteria.
# Return True if it's a match, False otherwise.
# First establish if parent of JobCheckpoint is 'self' (this job)
# if so, then check if search criteria for JobCheckpoint match,
# glue fields with something like:
return field_glue.operate(condition_results)
elif domain_object is JobCommand:
# (...)
if domain_object.parent_job == self:
# see if conditions pan out
return field_glue.operate(condition_results)
class JobCheckpoint(DomainObject):
def __init__(self, name, start, end, status, job_commands: List['JobCommand'], parent_job: Job):
self.name = name
self.start = start
self.end = end
self.status = status
self.job_commands = job_commands
# For easier reference;
# e.g. when search criteria matches this JobCheckpoint
# then Job associated to it can be found
# more easily.
self.parent_job = parent_job
class JobCommand(DomainObject):
def __init__(self, name, start, end, status, parent_checkpoint: JobCheckpoint, parent_job: Job):
self.name = name
self.start = start
self.end = end
self.status = status
# For easier reference;
# e.g. when search criteria matches this JobCommand
# then Job or JobCheckpoint associated to it can be found
# more easily.
self.parent_checkpoint = parent_checkpoint
self.parent_job = parent_job
class JobsCollection(DomainObject):
def __init__(self, jobs: List['Job']):
self.jobs = jobs
def get_jobs(self, filter: DomainObjectFilter) -> List[Job]:
return filter.apply(self)
def get_commands(self, job: Job) -> List[JobCommand]:
"""
Returns all commands for specified job (search criteria).
"""
result = []
for some_job in self.jobs:
if job.matches(some_job):
for job_checkpoint in job.job_checkpoints:
result.extend(job_checkpoint.job_commands)
return result
def get_checkpoints(self, job: Job) -> List[JobCheckpoint]:
"""
Returns all checkpoints for specified job (search criteria).
"""
result = []
for some_job in self.jobs:
if job.matches(some_job):
result.extend(job.job_checkpoints)
return result