MongoDB index with specific field value

Question

Good day!

I have a collection with documents like

{
  account_id: "accountOne"
  state: stateOne
}

I want to make sure that there is only one document that has pair accountID<->state, where state equals to stateOne, but I want to be able to have many documents where state equals to any value different from stateOne

For example I want to be able to have this data in my collection:

{
  account_id: "accountOne"
  state: stateOne
}

{
  account_id: "accountOne"
  state: stateTwo
}

{
  account_id: "accountOne"
  state: stateTwo
}

If I make uniq index like {account_id: 1, state: 1} I will get an error. Is there any way to do it via db ? Or I have to do it via my sevice logic?

Maybe provide us the command how you created the index. And the most important question: What do you mean by "I will get an error"? Please provide the error you get! — Wernfried Domscheit
– Wernfried Domscheit, Commented Mar 18, 2022 at 10:05
If I make uniq index on {account_id: 1, state: 1} fields I could not create several documents with "state: stateTwo" - I will get duplicate key index error on insert — RedCollarPanda
– RedCollarPanda, Commented Mar 18, 2022 at 10:11
What is the criteria that distinguishes stateOne from other states (other than that there can be only one stateOne that is associated with an account_id). — prasad_
– prasad_, Commented Mar 18, 2022 at 11:49

Wernfried Domscheit · Accepted Answer · 2022-03-18 10:45:37Z

1

Try this one:

db.collection.createIndex(
   { account_id: 1, state: 1 },
   { unique: true, partialFilterExpression: { state: stateOne } }
)

answered Mar 18, 2022 at 10:45

Wernfried Domscheit

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