I'm using a modified second approach.

1. Create a base abstract class with all properties:

Class model.PersonBase Extends (%XML.Adaptor, %JSON.Adaptor) [ Abstract ]
{

Property Name;

}

2. Create persistent class:

Class model.Person Extends (%Persistent, model.PersonBase, Utils.Copyable
{
/// Indices, fkeys and relationships go here
}

Utils.Copyable allows easy copy/compare.

3. Create snapshot class:

Class model.PersonSnapshot Extends (%Persistent,  model.PersonBase, Utils.Copyable)
{

Index parentIndex On parent;

/// Creation timestamp (UTC)
Property createdOn As %TimeStamp(POPORDER = -1, XMLPROJECTION = "NONE") [ InitialExpression = {$ZDATETIME($ZTIMESTAMP, 3, 1, 3)}, Required ];

Property parent As model.Person(XMLPROJECTION = "NONE");

Method %OnNew(parentId As %Integer) As %Status [ Private, ServerOnly = 1 ]
{
    #dim sc As %Status = $$$OK
    
    set ..parent = ##class(model.Person).%OpenId(parentId,, .sc)
    if $$$ISERR(sc) quit sc

    quit ..copyFrom(..parent, ##class(model.PersonBase).%ClassName(1))
}

}

And done.

This way you can add a snapshot of object at any point of time and by calling compareTo calculate a diff between any two versions.

There's also a hash function you can use to calculate hash from some or all object properties to speed up equivalence checks.

Check %Client.HttpResponse.StatusCode

Yes, I caught the same behavior. Looks like a bug.

Reported. Please file a wrc if you want to be notified about any changes.

Calling @Robert.Kuszewski.

Something like this?

SELECT
    ID,
    name,
    processedDate,
    processedTime
FROM MYprocesses m
WHERE NOT EXISTS (  SELECT 1
                    FROM MYprocesses m1
                    WHERE 1=1
                        AND m1.name=m.name
                        AND TO_POSIXTIME(m1.processedDate||' '||m1.processedTime, 'yyyy/mm/dd hh:mm:ss') > TO_POSIXTIME(m.processedDate||' '||m.processedTime, 'yyyy/mm/dd hh:mm:ss'))

Replace TO_POSIXTIME with TO_TIMESTAMP on older versions.

If record ids are aligned with time (meaning higher id has higher processed date/time) you can simplify and speed up the query:

SELECT
    ID,
    name,
    processedDate,
    processedTime
FROM MYprocesses m
WHERE NOT EXISTS (  SELECT 1
                    FROM MYprocesses m1
                    WHERE 1=1
                        AND m1.name=m.name
                        AND m1.id>m.id)

Interoperability callbacks can now be written in Python.

Class dc.DFOperation Extends Ens.BusinessOperation
{

Method OnMessage(ByRef request As Ens.StringContainer, Output response As Ens.Response) As %Status [ Language = python ]
{
    import pandas
    import iris

    query = request.value.StringValue
    response.value = iris.cls('Ens.Response')._New()
    
    stmt = iris.sql.prepare(query)
    rs = stmt.execute()
    df = rs.dataframe()
    
    iris.cls('Ens.Util.Log').LogInfo("dc.DFOperation", "OnMessage", "Dataframe load success")
    
    return iris.cls('%SYSTEM.Status').OK()
}

}

Please consider providing a code sample.

Is it just a SELECT * FROM table query or is it something else?

Run the query in a Management Portal and compare the timings.

SELECT Name
FROM %Dictionary.CompiledIndex
WHERE PrimaryKey = 0 AND parent = 'your.class'

From the docs:

• <STRINGSTACK> An expression is too long, there are too many expressions in an argument for a single command, or an expression contains many very long strings. Simplify the expression.
• <MAXSTRING> There has been an attempt to specify or create a data string longer than the implementation allows. The maximum string size is 3,641,144 characters. Attempting to concatenate strings that would result in a string exceeding this maximum string size results in a <MAXSTRING> error.

MAXSTRING is always related to maximum length of 3,641,144 characters for one string (assuming long strings are enabled). STRINGSTACK can be raised in several different circumstances, including a lot of small strings, recursion and so on.

Increasing bbsiz may help avoid STRINGSTACK error, but not MAXSTRING.

In your case use streams by replacing:

set file=object.%Get(i).file

with:

set file=object.%Get(i).%Get("file",,"stream")

Here's how to debug interoperability hosts anywhere: on Windows, Linux, and Mac, in Containers.