我有一个简单的集合。
> db.y.find({}, {'_id': 1})
{ "_id" : ObjectId("5908e63cd15fa104356eaf64") }
{ "_id" : ObjectId("5908e63cd15fa104356eaf65") }
{ "_id" : ObjectId("5908e63cd15fa104356eaf66") }
{ "_id" : ObjectId("5908e63cd15fa104356eaf67") }
{ "_id" : ObjectId("5908e63cd15fa104356eaf68") }
{ "_id" : ObjectId("5908e63cd15fa104356eaf69") }
{ "_id" : ObjectId("5908e63cd15fa104356eaf6a") }
{ "_id" : ObjectId("5908e63cd15fa104356eaf6b") }
我想操作一个简单的聚合管道(在很大程度上简化了解释(
我运行此mongo shell脚本:
print('find')
result = db.y.find({ '_id': ObjectId("5908e63cd15fa104356eaf64") }, {'_id':1})
while ( result.hasNext() ) { printjson( result.next() ); }
print('aggregate match direct')
result = db.y.aggregate( [ {'$match': {'_id': ObjectId("5908e63cd15fa104356eaf64") } }, {'$project': {'_id': 1}} ] )
while ( result.hasNext() ) { printjson( result.next() ); }
print('aggregate match with $eq')
result = db.y.aggregate( [ {'$match': {'_id': {'$eq': ObjectId("5908e63cd15fa104356eaf64") } } }, {'$project': {'_id': 1}} ] )
while ( result.hasNext() ) { printjson( result.next() ); }
print('aggregate match with $ne')
result = db.y.aggregate( [ {'$match': {'_id': {'$ne': ObjectId("5908e63cd15fa104356eaf64") } } }, {'$project': {'_id': 1}}, {'$limit': 5} ] )
while ( result.hasNext() ) { printjson( result.next() ); }
使用此结果(这是绝对正确的(
find
{ "_id" : ObjectId("5908e63cd15fa104356eaf64") }
aggregate match direct
{ "_id" : ObjectId("5908e63cd15fa104356eaf64") }
aggregate match with $eq
{ "_id" : ObjectId("5908e63cd15fa104356eaf64") }
aggregate match with $ne
{ "_id" : ObjectId("5908e63cd15fa104356eaf65") }
{ "_id" : ObjectId("5908e63cd15fa104356eaf66") }
{ "_id" : ObjectId("5908e63cd15fa104356eaf67") }
{ "_id" : ObjectId("5908e63cd15fa104356eaf68") }
然后,我想将其转换为Python,如下所示:
...
print('find')
result = y.find({ '_id': 'ObjectId("5908e63cd15fa104356eaf64")' }, {'_id':1})
for i, o in enumerate(result):
print(i, o)
print('aggregate match direct')
result = y.aggregate( [ {'$match': {'_id': 'ObjectId("5908e63cd15fa104356eaf64")' } }, {'$project': {'_id': 1} } ] )
for i, o in enumerate(result):
print(i, o)
print('aggregate match with $eq')
result = y.aggregate( [ {'$match': {'_id': {'$eq': 'ObjectId("5908e63cd15fa104356eaf64")' } } }, {'$project': {'_id': 1} } ] )
for i, o in enumerate(result):
print(i, o)
print('aggregate match with $ne')
result = y.aggregate( [ {'$match': {'_id': {'$ne': 'ObjectId("5908e63cd15fa104356eaf64")' } } }, {'$project': {'_id': 1} }, {'$limit': 5} ] )
for i, o in enumerate(result):
print(i, o)
与此结果:
find
aggregate match direct
aggregate match with $eq
aggregate match with $ne
0 {'_id': ObjectId('5908e63cd15fa104356eaf64')}
1 {'_id': ObjectId('5908e63cd15fa104356eaf65')}
2 {'_id': ObjectId('5908e63cd15fa104356eaf66')}
3 {'_id': ObjectId('5908e63cd15fa104356eaf67')}
4 {'_id': ObjectId('5908e63cd15fa104356eaf68')}
结论:
$匹配操作永远不会考虑objectid语法。
如何正确编写?
感谢任何提示
基督徒
您必须在标准库中使用objectid类
from bson.objectid import ObjectId
result = y.find({ '_id': ObjectId("5908e63cd15fa104356eaf64") }, {'_id':1})
可能相关
现在,比赛并找到字段正在询问_id是否是一个名为" ObjectID(" 5908E63CD15FA104356(的字符串"。但是,在Python中,您必须首先与ObjectID类别分配一个唯一的标识符
您的最后一场比赛实际上是在打印所有内容,因为您询问所有_ids是否不等于字符串" ObjectId(" 5908E63CD15FA10435644((",而不是objectid