Instant should persist the same way (BsonType.DATE_TIME) as LocalDateTime and Date

[codeconsole]

class Person {
    LocalDateTime created
    Date updated
    Instant modified
}

results in inconsistent mongo storage.

  {
    _id: '68e0824c605bbe8f074c52ba',
    created: ISODate('2025-10-04T02:11:24.201Z'),
    updated: ISODate('2025-10-04T02:11:24.201Z'),
    modified: Long('1759543884201'),
    version: Long('0')
  }

Spring Data persists Instant the same way as Date. So for mongodb it is stored as a BSON DateTime (displayed as ISODate(...)). That’s the correct and expected mapping. Grails, however, stores it as a Long.

Aggregation stages or queries that expect date types:
$year, $month, $week, $dayOfWeek
$dateTrunc, $dateAdd, $dateSubtract
$dateToString, $dateFromParts

so none of this works with the current Instant > Long implementation

Similar to Spring Data, the following should be interchangeable without requiring a database update:

    Date created
    LocalDateTime created
    Instant created

[matrei]

LGTM! Good catch!

However, how will this effect existing applications using grails-data-mongodb?
Should we document that the field type in the database must be updated when people upgrade?

[jdaugherty]

My only concern with this is the upgrade guide was not updated to mention this change.

[codeconsole]

However, how will this effect existing applications using grails-data-mongodb?

@matrei If anyone out there is actually using Instant, it will thrown an exception. The data must be fixed. Fortunately, there is an easy mongosh solution which I posted in UPGRADE7.md

Should we document that the field type in the database must be updated when people upgrade?

done and a mongosh update example was provided.