MongoDB 聚合管道，$gte，$lte？

Question

I have a document for software that contain these fields _id, category, brand etc. There is a price field which is of type string. Some documents have invalid prices or are null. I want to use an aggregation pipeline so that the price is >=4 and <=8 and convert the price to double. There is also a date field that I want to be >=10. I also want to use $out to create a new collection of this document. I have done this so far, I was wondering if someone could let me know how I can retrieve the documents but I don't want to lose or change the other fields only the Price and date.

db.sw.aggregate([{$match: {}}, 
{$project: {priceLen: {"$strLenCP": "$price"}}}, 
{"$match": {priceLen: {"$gte": 4, "$lte": 8}}}, 
{$project: {price: {$trim: {input: "$price", chars: "$"}}}}, 
{$project: {price: {$toDouble: "$price"}}}]) 

my thought process for the $match was to retrieve all the fields. Any help will be really appreciated.

Answer 1

No idea what your requirements are in terms of being "correct".

$project removed all fields (apart from _id ) and populates the given fields. If you like to keep existing fields use $set or the alias $addFields which names the actual operation.