Problems encountered during the initial use of Mongodb

1. String to String[]

Because a lot of data is migrated from mysql, there are fields like '123,456'

On the mysql side, you can use the find_in_set() function to query. I haven’t found a similar one on the mongodb side. I just thought that I could convert this into a string array, and then I could add an index to it.

db.dev_mc.update(
    {"_id": 82839}, #匹配条件
    [
        {$set:{mcUid:{$split: ["$mcUid", ","]}}}
],
{ multi: true })

#全表修改就是
db.dev_mc.update(
    {},
    [
        {$set:{mcUid:{$split: ["$mcUid", ","]}}}
],
{ multi: true })

2. split cutting display

db.getCollection("dev_mc").aggregate([{
    $project: {
        "mcUid": "$mcUid",
        "split": {$split: ["$mcUid", ","]}
    }
}])