LAST_IDENTITY() returns the ID of the last record inserted, updated, or deleted. This is very useful from ODBC/JDBC. From within an ObjectScript method, you can access this directly instead of running an additional SELECT statement:
^rMAC("your routine")
@Nicholai Mitchko's example above is Python calling an ObjectScript method that has pass-by-ref arguments, and that works as he described. I wondered if Python methods could be written to return values in their arguments, despite the fact that Python doesn't have pass-by-ref arguments. The answer is "yes," but only if the caller passes in a data structure (like a list or a dict) that the Python method modifies. Otherwise, arguments to a Python method called from either ObjectScript or Python can't return values.
If you make a loooonnnnng $piece-delimited string, and a lonnnnnnnnng $list, and you loop 1000000 times, accessing random pieces and random $list items, and sum up the time, and divide by 1000000, you'll find that for access, $lists are faster than delimited strings. At least that's what I saw when $list first appeared. But my mentor from that time said "Yes Joel, they are faster, but $list was added to ObjectScript so that we wouldn't have to worry anymore about delimiters, and sub-delimiters, and sub-sub-delimiters, etc."
True. I personally am not a fan of using #dim in any way other than:
#dim variable as objectclassname
because it makes it clear that #dim provides code completion for object variables, which is the functionality I care about. Yes, I know it also provides variable documentation for developers who are used to declaring datatypes in other languages
The other documented options:
#dim variable as objectclassname = initialvalue (ok, but I prefer #dim followed by set)#dim variable = initialvalue (there's no reason to use #dim to do what set does)#dim variable as non-objectclassname (this is documentation only; no code completion is provided)#dim variable as list/array of objectclassname (again, documentation only; no code completion)It's not a big difference between Studio and VS Code - ObjectScript here. Studio automatically does the #dim for you when you do a %New() or %OpenId(), and VS Code - ObjectScript doesn't. But #dim is still necessary in both IDEs for referenced or returned objects:
set person = ##class(Simple.Person).%New() // Studio WILL provide code completion for person, VS Code WON'T #dim address as Simple.Address // without #dim, neither Studio nor VS Code will provide code completion for address set address = person.Address #dim rs as %SQL.StatementResult set rs = statement.%Execute(args) // you'll get code completion for rs thanks to #dim
Since Trigger code is called after validation and constraint checking, a trigger should not be used to change column values. David's solution is better.
I think you get everything from secondary superclass(es) except indexes, storage, and relationships.
Thanks Michael.
You could code it the oop way, and use $sortbegin on all the index globals for your multiple tables, which means you'd have to know or look up what the index global names are (since they're not always ^D and ^I anymore), and test 1000000 inserts (main table and referenced tables) with the index build deferred to the end, and time it to see how long it takes.
And then code it the sql way, inserting the same data into the multiple tables using %NOINDEX, and calling %BuildIndices() on all the classes at the end, and time it to see how long that takes. The sql way is supposed to be faster...
@Alex Woodhead Why are you using $sortbegin on the ^D global? Just to show it's possible in this demo? Or are you recommending that general approach? It seems to me that the solution to the original question would be allowing the data to save normally (not using $sortbegin on the ^D global), and using $sortbegin on the ^I global and discarding those updates.
@Michael Fortunato Please tell us the reason for wanting to do this. It can't be that you want the index to be permanently out of sync with the data. Perhaps it's for performance for many inserts? If so, switching to a SQL approach with %NOINDEX (as @David.Satorres6134 suggested) is a good idea.
Would <foreach> help here? https://docs.intersystems.com/irislatest/csp/docbook/DocBook.UI.Page.cl…
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So this thread has clarified that the transaction that you read about in the docs is the transaction inside %Save(), and %OnSaveFinally() is a callback for %Save(). Your original question seems to be asking if the TCOMMIT command itself triggers a callback, but it doesn't. You could of course add your own code right after the TCOMMIT, but I guess that's not what you're looking for with this question.
A little bit more detail. The queries in %SYSTEM.License are not defined as [SqlProc]s. Therefore, they can't be called from outside IRIS, including from Python. To get the information returned by these queries in Python, you should write your own method in ObjectScript, that runs the query with the (deprecated) %Library.ResultSet class. As you loop through the results:
...and it appears that Mr C is also trying to sneak in a new abbreviation for ObjectScript: ISOS. 
Ah, I misinterpreted "this alias" in your post! So you meant (I added italicized text): "I like to define :sql as a way to launch the shell and execute a statement - so that means this built-in :sql alias should be renamed by InterSystems to something else!! or be removed."
At least aliases defined in .iris_init override any built-in aliases.
I have one older IRIS instance (unreleased v2021.1 with some Python extras) that has the following aliases built in. The :sql alias doesn't run Execute() like it seems to do on yours.
:py Do $system.Python.Shell() :mdx Do $system.DeepSee.Shell() :sql Do $system.SQL.Shell() :tsql Do $system.SQL.TSQLShell()
Here's some info that was inadvertently removed from the docs, but will be returning soon:
On Unix systems, if a file named ~/.iris_init exists, it is read when a terminal session is initiated. Only lines starting with :<command> are processed. All other lines are ignored. This file accepts only :alias commands, which enables you to store favorite command abbreviations there.
Example of a ~/.iris_init file:
# Initial aliases
:alias % zn "%SYS"
:alias load Do $System.OBJ.Load("$1",$S("$2"="":"ck",1:"$2"))
:alias ut Do ##class(%UnitTest.Manager).RunTest("$1"):alias sql do $system.SQL.Shell()
:alias err do $system.Status.DisplayError($1)
VS Code - ObjectScript doesn't prevent <SUBSCRIPT> errors. For example, the statement
set b(x) = c
can't be checked by the IDE since it doesn't know if the value of x will be "" or not at runtime.
Nice article about an important question: when should you touch the storage definition? Some comments on the scenarios (with sound effects!). The only modifications I'd make to the bookshelf analogy is that there are gazillions of shelves (every person gets their own shelf) using the mapping of what type of book goes in each slot.
update schema.table set property = null(cue computer bleeps).Editing the name of any unused slot in the storage definition and adding "-unused" to make things clear could be OK but it's definitely not intended for that use. I'm not sure it's necessary to do anything in this case; If I see a slot in the storage definition named XYZ and there's no property XYZ, I know it's an unused slot. Maybe preceding the storage definition with a comment section would be cleaner:
/* unused slots XYZ (as of 1/1/2020) ABC (as of 6/1/2021) */
Please let me know if it's not clear, or if I missed a scenario.
I added Steve's suggestion, not because he asked twice, but because I owe him some money. 
Thanks to @Muhammad Waseem I'm posting an updated version of the "Cheat Sheet."
Very strange! I was never on the standards committee. I started using MUMPS in 1987, and I remember it differently ($next being replaced by $order). Let me check the archives...
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All I can say is Wow! I experienced many of the same things over my career, but I was living in safe, protected, training-room-land, not the real world of development like Nigel. Great article!
I'll just note that Nigel says "might" in the title. 
One thing that confused me, Nigel. You wrote "If one of the early MUMPS creators had called $order "$next", it would immediately be recognizable as Next()...". But I know that you know that the original $order was called $next.
Hi Robert,
Why did you say that the %TimeStamp datatype is the equivalent of the full $h? It's true that %Date/%Time do the conversion from internal date/time values to/from external. But %TimeStamp, %DateTime, and %StringTimeStamp do not do any internal/external conversion. It's just for the YYYY-MM-DD HH:MM:SS external timestamp. Is there something I'm missing?
%PosixTimeStamp does convert, but it's not $h internally.
Thanks! One more followup question: Does all of the above now supersede the following setting?
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I think Ben meant:
set a.test = 1Thanks Dmitry. I added this, which will launch the current class if it's a Zen page. Not perfect, but fun!
"links":{"Launch Zen page": "http://${host}:${port}/csp/${namespace}/${classname}.cls"
The popup help for "links" states "Several ${...} substitution symbols are supported in the value." Is there a list somewhere of what is supported? I tried ${file} but that didn't work.