By the way, InterSystems employees have already given examples of undocumented code here, which can be found independently in %SYS:

• https://community.intersystems.com/post/there-way-get-internal-private-p...
• https://community.intersystems.com/post/what-best-way-serialize-objectli...

If you look at a modern version of Caché or IRIS you'll find that ^%SYS.SECURITY is hidden.

What does the source code of ^%SYS.SECURITY have to do with it? The fact that it is hidden does not play any role here.

Take a look at the code %CSP.Portal.Home:%OnPreHTTP()

I keep my promise (yes, it wasn't an April Fool's joke ;)

• The first way is associated with a dummy field for the sake of being able to override the final BuildValueArray method and avoid the following error

  ERROR #5272: Can't change final 'Method' : 'BuildValueArray')

  Class rcc.IC.ItemList Extends (%Persistent, %Populate) [ Final ]
  {
  
  Index xitmp On (ItemsP(KEYS), ItemsP(ELEMENTS));
  
  Property Company As %String [ Required ];
  
  Property Region As list Of %String(COLLATION = "EXACT", POPSPEC = ":4", VALUELIST = ",US,CD,MX,EU,JP,AU,ZA") [ Required ];
  
  Property Items As list Of rcc.IC.serItem(POPSPEC = ":4") [ Required ];
  
  Property ItemsP As %String(COLLATION = "EXACT") [ Calculated, Private, ReadOnly, Required, SqlComputeCode = {s {*} = {Items}}, SqlComputed ];
  
  ClassMethod ItemsPBuildValueArray(
    value,
    ByRef array) As %Status
  {
    s ptr=0
    while $listnext(value,ptr,val){
      s v=$li(val,1),
        array($li(v,1))="Subject",
        array($li(v,2))="Change",
        array($li(v,3))="Color"
    }
    q $$$OK
  }
  
  }

  select count(ID) from rcc_IC.ItemList where FOR SOME %ELEMENT(ItemsP) (%key in ('blue','yellow') and %value='Color')

  or if need to find values in any fields

  select count(ID) from rcc_IC.ItemList where FOR SOME %ELEMENT(ItemsP) (%key in ('blue','yellow'))

  For the sake of speed, you can store in the index not all the fields of the serial class, i.e.:

  Index xitmp On ItemsP(KEYS);
  
  ClassMethod ItemsPBuildValueArray(
    value,
    ByRef array) As %Status
  {
    s ptr=0
    while $listnext(value,ptr,val){
      s v=$li(val,1),
        array($li(v,3))="" ; only Color
    }
    q $$$OK
  }

  select count(ID) from rcc_IC.ItemList where FOR SOME %ELEMENT(ItemsP) (%key in ('blue','yellow'))

  You can also add more dummy fields and accordingly indexes to cover all possible queries.

---

• The second way involves changing the storage and creating a virtual table

  Class rcc.IC.ItemList Extends (%Persistent, %Populate) [ Final ]
  {
  
  Index xitm On Items(ELEMENTS).Color;
  
  Index xitm1 On (Items(ELEMENTS).Color, Items(KEYS));
  
  Property Company As %String [ Required ];
  
  Property Region As list Of %String(COLLATION = "EXACT", POPSPEC = ":4", VALUELIST = ",US,CD,MX,EU,JP,AU,ZA") [ Required ];
  
  Property Items As list Of rcc.IC.serItem(POPSPEC = ":4", STORAGEDEFAULT = "array") [ Required ];
  
  }

  select count(distinct ID) from rcc_IC.ItemList where ItemList_Items->Items_Color in ('blue','yellow') -- index "xitm1" is used

  or even faster

  select count(ID) from rcc_IC.ItemList where FOR SOME %ELEMENT(Items) (%Value in ('blue','yellow')) -- index "xitm" is used

  Of course, the data can be accessed from both tables, just do not forget about SetCollectionProjection GetCollectionProjection (for more information, see my article SQL index for array property elements)

It is better to check this with your license, as it is likely that some of its options, such as Web Add-on, may affect this (see $SYSTEM.License.PublicWebAppUser).

Hi Robert.

I also got carried away with this question and found two more ways to use indexes for a list of serial objects, and you can explicitly specify specific fields in the query, rather than $list (%Value,3).

The speed may be not always the best, but I did the best I could. I tested on Caché (perhaps something has been improved in IRIS in this regard?)

If you're interested, I can share it.

See Working with Streams

Topicstarter indicated Caché 2018.1, which is no longer being developed so not may change in the future (not counting security patches)

Unfortunately, %INLIST does not use indexes (at least it was in Caché, I do not know how it is now in IRIS), which I made a note about in my article.

$LISTFIND certainly does its job well, but there is a better solution.

As the data grows, the search speed will drop, since this solution does not use indexes in any way.
Therefore, the best solution is to use the predicate FOR SOME %ELEMENT.

For more details with examples, see one of my articles: SQL Performance Resources (item k. Indexing of non-atomic attributes)

The interactive tutorials with exercises built into the documentation helped me a lot in my time:

• Caché Tutorial Topics Map
• Caché Tutorials

Also included was a database "SAMPLES" (code and data) with examples for every taste. I often used it for performance testing.

In addition, in the <cachesys>\dev\ folder there were numerous demos with source code for various programming languages and connection technologies (С++, C#, Java, PHP, Python, ODBC, JDBC, ADO.NET, ActiveX, XEP, etc.):

\dev\tutorials\
\dev\tutorials\csp
\dev\tutorials\java
\dev\tutorials\mv
\dev\tutorials\pojo
\dev\tutorials\security
\dev\tutorials\UnitTestEx
\dev\tutorials\webservices
\dev\tutorials\zen

\dev\Cache\
\dev\Cache\callin
\dev\Cache\callout
\dev\Cache\cctrlcpp
\dev\Cache\cctrlvb
\dev\Cache\ctrldemo
\dev\Cache\HAcluster

\dev\odbc\samples\
\dev\odbc\samples\php
\dev\odbc\samples\select
\dev\odbc\samples\sqlgateway

\dev\python\
\dev\python\samples
\dev\python\samples3

\dev\cdirect
\dev\cpp\samples
\dev\dblib\samples
\dev\dotnet\samples
\dev\java\samples
\dev\mv\samples
\dev\node.js\samples
\dev\perl\samples

And now it's right?

N<=9 (59 chr)

N>9 (62 chr)

Who is shorter? ;)

Sorry, I didn't notice. Updated

Examining an XML Subtree

  try{

    $$$ThrowOnError(##class(%XML.XPATH.Document).CreateFromString("<a><b><c>some content</c></b></a>", .doc))
    $$$ThrowOnError(doc.EvaluateExpression("/a", "b", .field))
    #dim obj As %XML.XPATH.DOMResult = field.GetAt(1)
    
    while obj.Read() {
      if obj.HasValue {
        write obj.Path,": ",obj.Value,!
      }
    }
    
  }catch(ex){
    write "Error ", ex.DisplayString(),!
  }

Result:
b\c: some content