If you want to transfer data via REST check RESTForms project (part 2).

Mimedata is subscripted by name and index.

So in your case:

set name = "BulkFileUpload"
for i=1:1:%request.CountMimeData(name)
    set mimeData = %request.GetMimeData(name, , i)
}

On each iteration mimeData variable would hold the stream with one next mimedata.

%request is simply an object of %CSP.Request class, check the docs or code to know how it works.

Additionally you can use this snippet to see what's inside %request, %response and %session objects:

set %response.ContentType = "html"
do ##class(%CSP.Utils).DisplayAllObjects()
quit $$$OK

<FILEFULL>  - Caché attempted to allocate a disk block for more global data or routine storage, but the attempt failed because the Caché database is full and could not be expanded.

Affected db is /hs-connect-hom/db/BPINTEGRADEV-GLB.

The easiest way is to use JSON_OBJECT for everything. Fastest would be just writing to device from resultset. Combine these approaches to get the performance you need (add this code to Parent class and call Test method):

Query Display() As %SQLQuery
{
SELECT
    JSON_OBJECT(
        'ID':%ID,
        'Name': Name,
        'Description': Description,
        'Children':    Example.Parent_GetChildrenInfo(%ID)
    )
FROM Example.Parent
}

/// do ##class(Example.Parent).Test()
ClassMethod Test(count = 0)
{
    if count>0 {
        do ##class(Example.Child).%KillExtent()
        do ..%KillExtent()
        
        
        do ##class(Example.Child).Populate(count,,,,$$$NO)
        do ..Populate(count,,,,$$$NO)
    }
    
    do ..DisplayFunc().%Display()
}

ClassMethod GetChildrenInfo(id) As %String [ SqlProc ]
{
    #define CRLF                             $c(13,10)
    #define ZENJSISNUM(%val)                ($IsValidNum(%val)&&(%val=+(%val)))
    #define ZENJSNUM(%num)                    $fnumber(%num,"LON")
    #; JSON utility macros that use the JSON translation table instead of the JS translation table
    #define ZENJSTABLE(%format)                ("JS"_$S(%format["u":"ML",1:""))
    #define ZENJSONTABLE(%format)            ("JSON"_$S((%format["u"):"ML",1:""))
    #define ZENJSONESCAPE(%str,%format)        $S(%format["s":$ZCVT(%str,"O",$$$ZENJSONTABLE(%format)),1:$Replace($ZCVT(%str,"O",$$$ZENJSTABLE(%format)),"\'","'"))
    #define ZENJSONSTR(%str,%format)        (""""_$$$ZENJSONESCAPE(%str,%format)_"""")
    #define ZENJSONPROP(%prop,%format)        $$$ZENJSONSTR(%prop,%format)
    #define ZENJSONVALUE(%val,%format)        $S($$$ZENJSISNUM(%val):$$$ZENJSNUM(%val),$C(0)=(%val)||$ListValid(%val):"""""",1:$$$ZENJSONSTR(%val,%format))
    #define ZENJSONPAIR(%pr,%val,%format)    $$$ZENJSONPROP(%pr,%format)_":"_$$$ZENJSONVALUE(%val,%format)
    
    set out = "["   
    
    
    set ids = ..ChildrenGetStored(id)
    set ptr=0
    set separator=0
    while $listnext(ids,ptr,value) {
        set value = $lg(value)
        set:separator out = out _ ","

        set out = out _  "{"
        set out = out _  $$$ZENJSONPAIR("Name",##class(Example.Child).NameGetStored(value),"") _","
        set out = out _  $$$ZENJSONPAIR("Description",##class(Example.Child).DescriptionGetStored(value),"")
        set out = out _  "}"
        set separator = 1
    }
    
    set out = out _  "]"
    
    quit out
}

I think it would be better to do with REST, but SQLQuery tag can do what you want.

Add

Include Ensemble

to the start of the cube class.