The allInstancesAtTime operator queries the database's history tables to reconstruct the state of all instances of a specific Class exactly as they existed at a given point in time. It is used for auditing, historical reporting, and comparing past states to current states.

Prerequisites: The Versioned Property

For this operator to work, the MDriven execution engine must be actively recording history for the target class.

• You must select the Class in the MDriven Designer and set its Versioned property to True.

Syntax & Parameter Type

A common misconception is that this operator takes a standard DateTime object. It actually requires an Integer

ClassName.allInstancesAtTime(timeStamp : Integer)

To bridge the gap between calendar dates and MDriven's integer timeline, you can use the .timeToTimeStamp converter on your DateTime value.

1. Fetching from a Specific Date and Time

Use DateTime.Parse (or DateTime.Create) and immediately convert it to a TimeStamp integer.

Complaint.allInstancesAtTime(DateTime.Parse('2025-01-01 00:00:00').timeToTimeStamp)

2. Fetching Relative to the Current Time

You can calculate a date relative to today (e.g., 30 days ago) and convert that to a TimeStamp.

Complaint.allInstancesAtTime(DateTime.Now.AddDays(-30).timeToTimeStamp)

Common Errors & Troubleshooting

Error: System.DateTime does not conform to System.Int32

• Cause: You passed a DateTime object directly into the operator.
• Solution: Append .timeToTimeStamp to your DateTime expression to convert it into the required Integer format.

Error: Specified method is not supported. ,InternalEvaluate()...

• Cause: You are calling allInstancesAtTime on a class that does not have history tracking enabled. The EcoSpace cannot execute the temporal query because the history tables do not exist.
• Solution: Go to your model, set the Class's Versioned property to True, and update your database schema.

See also: allInstances