Okay, then you need to use your original storage definition, but when selecting invalid, select it in a NVL function:

SELECT
ID, Code, Description, NVL(Invalid, 0)
FROM Wendy.LTCodes

It should return 0 instead of empty string.

Runtime Variables are for that purpose.

And if you want to apply filter to any MDX query against a cube, you can specify a %OnGetFilterSpec callback.

These changes fixed it:

• Removed highlited part of storage definition
• Made invalid property Transient
• Added 0 default to $Get

Class Wendy.LTCodes Extends %Persistent [ StorageStrategy = LTCStorage ]
{

Property Code As %String;

Property Description As %String;

Property Invalid As %Library.Boolean [ SqlComputeCode = { set {*} = ##class(Wendy.LTCodes).GetInvalid({Code})}, SqlComputed, Transient ];

Index CodeIndex On Code [ IdKey, PrimaryKey, Unique ];

ClassMethod GetInvalid(WSCode) As %Boolean
{
    Quit $G(^LTCODES(WSCode,"INVALID"),0)
}

Method InvalidGet() As %Boolean
{
    Quit ..GetInvalid(i%Code)
}

Method InvalidSet(value As %Boolean) As %Status
{
    Set ^LTCODES(i%Code,"INVALID")=value
    quit $$$OK
}

/// Do ##class(Wendy.LTCodes).SetData()
ClassMethod SetData()
{
    kill ^LTCODES
    S ^LTCODES("N001")="ANYOLD DESC"
    S ^LTCODES("N001","INVALID")=1
    S ^LTCODES("N002")="C5 REPEAT 1"
    S ^LTCODES("N111")="SPECIMEN COMMENT"
    S ^LTCODES("N200")="MSUD SCREEN|MSUD"
    S ^LTCODES("N500")="Sickle Cell Screen"
}

Storage LTCStorage
{
<SQLMap name="LTCMap">
<Data name="Description">
<Delimiter>"|"</Delimiter>
<Piece>1</Piece>
</Data>
<Global>^LTCODES</Global>
<Subscript name="1">
<Expression>{Code}</Expression>
</Subscript>
<Type>data</Type>
</SQLMap>
<StreamLocation>^Wendy.LTCodesS</StreamLocation>
<Type>%CacheSQLStorage</Type>
}

}

You can define a property of  %Stream.Object class and store %Stream.FileBinary/%Stream.FileCharacter there.

I removed InvalidGet method and object access to the property stopped working.

Class Utils.GlobalProp Extends %Persistent
{

Parameter InvalidGLVN = "^Utils.GlobalPropP";

Property Invalid As %String [ SqlComputeCode = {set {*} = ##class(Utils.GlobalProp).InvalidStatic()}, SqlComputed, Transient ];

ClassMethod InvalidStatic() As %String
{
    Return $Get(@..#InvalidGLVN)
}

Method InvalidSet(val As %String) As %Status
{
    Set @..#InvalidGLVN = val
    Return $$$OK
}

/// Do ##class(Utils.GlobalProp).Test()
ClassMethod Test()
{
    Do ..%KillExtent()
    Set obj = ..%New()
    Write "Invalid old: " _ obj.Invalid,!
    Set obj.Invalid = $Random(100)
    Write "Invalid new: " _ obj.Invalid,!
    Do obj.%Save()
    Kill obj
    &sql(SELECT Invalid INTO :invalid FROM Utils.GlobalProp WHERE Id = 1)
    Write "SQLCODE: " _ SQLCODE,!
    Write "Invalid sql: " _ invalid,!
}

Outputs:

Invalid old:
Invalid new:
SQLCODE: 0
Invalid sql: 65

Related Int code:

zInvalidCompute(%id)
    New %tException,%val set %val = ""
    try {
    set %val = ##class(Utils.GlobalProp).InvalidStatic()
    } catch %tException { throw %tException }
    Quit %val
zInvalidGet() public {
    If i%Invalid = "" { Set ..Invalid=..InvalidCompute($listget(i%"%%OID")) } Quit i%Invalid }
zInvalidSQLCompute()
    // Compute code for field Invalid
 set %d(2) = ##class(Utils.GlobalProp).InvalidStatic()
 QUIT

    Do $System.Status.DisplayError(tStatus)
        Write !
    }
    Quit
}
}

I meant you write them. Here's the reference though.

This is not, generally a good idea to insert potentially long and slow code inside of object constructor.

Why? %OnNew should contain code which is absolutely required on object initiation regardless of the execution speed. There is no use case for this class to construct an object and not call %Connect, so %Connect should be moved into %OnNew. That way client code needs to make one mandatory call instead of two.

Here's working example:

Class Sample.XSLTransform [ Abstract ]
{

ClassMethod test(tData = "<HHSOS><DIAGNOSES><DIAGNOSIS_DATA><DIAGNOSIS_DATA_GUID>3762875</DIAGNOSIS_DATA_GUID><DIAGNOSIS_DATA_GUID>37628752</DIAGNOSIS_DATA_GUID></DIAGNOSIS_DATA><DIAGNOSIS_DATA></DIAGNOSIS_DATA><DIAGNOSIS_DATA></DIAGNOSIS_DATA><DIAGNOSIS_DATA_GUID>37628753</DIAGNOSIS_DATA_GUID></DIAGNOSES></HHSOS>", tSelect = "//DIAGNOSIS_DATA_GUID[1]", tXSL = "ExampleXSL")
{
    set tXML= ##class(%GlobalCharacterStream).%New()
    do tXML.Write(tData)
    set tXSL=##class(%Dictionary.CompiledXData).%OpenId($classname() _ "||" _ tXSL ).Data

    kill tParams
    set tParams("selectParam") = tSelect
    set tSC=##class(%XML.XSLT.Transformer).TransformStream(tXML,tXSL,.tOutput,,.tParams)
    zwrite tSC
    set tSC=tOutput.OutputToDevice()
}

XData ExampleXSL
{
<?xml version="1.0"?>

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
<xsl:param name="selectParam"/>
<xsl:template match="/">
    <xsl:copy-of select="$selectParam"/>
</xsl:template>
</xsl:stylesheet>
}

}

Example:

Do ##class(Sample.XSLTransform).test()
tSC=1
<?xml version="1.0" encoding="UTF-8"?><DIAGNOSIS_DATA_GUID>3762875</DIAGNOSIS_DATA_GUID><DIAGNOSIS_DATA_GUID>37628753</DIAGNOSIS_DATA_GUID>

tParams should be an array:

set tParms("tExperssion") = tExperssion
set tParms("tIndex") = tIndex

and this line:

<xsl:copy-of select="$tExperssion"/>

should maybe be:

<xsl:value-of select="$tExperssion"/>

You can change wildcard programmatically, see this topic. Though I think the better solution would be subclassing and calculating wildcard there.