如何使用正则表达式查询 pymongo 以获取仅包含数字的值

Question

I am working with a mongodb database where I have a particular value in some of the documents contain the field parentDocId, and others dont. Besides the ParentDocId is of many shapes, I would like to get 500 documents where that field not only exists but it is of 6 or more digits (no other character). This is the query I thought it work:

import pymongo
query = {"$and": [{'docReferences.parentDocId':{"$exists":True}},
{'docReferences.parentDocId':{"$regex": "^[0-9][0-9][0-9][0-9][0-9]*$"}}]}

But the query applied here does not work:

cur = DATA_collection.find(query).limit(500)
tic=datetime.now()
elements = []
for el in cur: 
    elements.append(el)
tac=datetime.now()
print(f'{tac-tic}')
print(len(elements))

this gives me a list of the THE SAME DOCUMENT 500 times and does not filter out documents with parentDocId like '1111'

Some idea what I am doing wrong?

NOTE: when using:

docReferences.parentDocId':{"$isNumber":True}

I get:

unknown operator: $isNumber,

Answer 1

The regex pattern for six or more digits (only) is ^[0-9]{6,}$ , so you may try:

import pymongo
query = {
    "$and": [
        { 'docReferences.parentDocId' : { "$exists" : True } },
        { 'docReferences.parentDocId' : { "$regex": "^[0-9]{6,}$" } }
    ]
}