Fair enough. Let's make this more fun! First of all, we need to understand the IDKEY index. InterSystems is somewhat unique in the market with this one. Most SQL vendors support indexes and most support "clustering" data with indexes to further improve the performance of certain queries. Think of our IDKEY index as the "Master Data Index" (sometimes referred to as the "Master Map" or "Data Map"). The "Master Data Index" (MDI) is simply the index that has every column "clustered" with it - all data values are present in the IDKEY index structure. Every table (persistent class) has an IDKEY index and every column (property in Object terms) is stored with it.

Any other index - not the MDI - is simply there to improve query performance. Each non-MDI index has an index key and perhaps some data clustered with it. InterSystems is not different from most other SQL implementations. You can create a new table and add indexes to it using standard DDL statements. We, like most vendors, have some non-standard syntax to support features unique to our product but it is mostly familiar syntax. You can also define a class directly using one of our IDE's or your favorite editor. And all of this will just work - no special effort required and your experience will be similar to that of using any other SQL. 

Your example is different. We support low-level storage mapping to legacy data structures. There are two additional storage classes that support this, one of which is used by your example - %CacheSQLStorage. This storage class was introduced specifically to provide a bridge from legacy applications to Caché/InterSystems IRIS. Mapping legacy data structures can be a complicated task and it can be confusing. And this is where you are - you have an application that is using our support for bridging existing data structures to our DBMS.

And none of that helps you with your problem! So let's try this. Let's define your class without using the legacy data mapping. I'll choose some simply data types just to illustrate.

Class User.Patient Extends %Persistent
{

Index AcctIndex On accountNo;

Property accountNo As %String;

Property citySt As %String;

Property dob As %Date;

Property name As %String;

Property patientNo As %Integer;

Property rel2Guar As %String;

Property sex As %String;

Property ssn As %String;

Property street1 As %String;

Property street2 As %String;

Property telephone As %String;

Property zip As %String;

}

That's it - no special work involved, just a quick and easy class definition with an index on accountNo defined. This is what it looks like in the SQL Manager:

This is an example without the legacy global mapping. %BuildIndices is automatically generated and there is nothing else you would need to do to define, populate and maintain this index - other than to build it initially if it was added to a previously populated extent.

In my next comment (this one is getting long), I'll convert the default storage structure into a mapped storage structure using %CacheSQLStorage.

Hi Keith,

%BuildIndices/%PurgeIndices are generated for any class that primarily extends %Library.Persistent. When such a class defines one or more indexes and that class uses SQL Storage then the class must also define an index map in the storage definition. Without that the index simply won't be maintained - it doesn't exist as far as SQL is concerned. Your display in the original posting is a view of the SQL table definition. The SQL table definition is a projection of the class definition to SQL.

Your first example shows an index that is defined as the IDKEY index - that is the index definition that corresponds to the SQL Master Map (data map). I'm not surprised that it doesn't show up in the indexes display of the SQL Manager.

If WRC isn't an option then a good place to start is to work through just one of your classes. If you can choose one simple example perhaps we can suggest corrections for you.

-Dan

There is a more general way to describe this situation. First consider what is actually happening. When you open an Object (%Open/%OpenId) you are copying data from persistent storage into memory. Then some other actor is modifying the data in persistent storage so the in-memory data is no longer the same as the data in persistent storage. If you were to then copy the in-memory data back to persistent storage (%Save), assuming the same identifier is used, then the modifications from the other actor would be overwritten.

There are two ways that Objects/SQL Persistence will allow this to happen (I call the action performed by the other actor an underwrite). First is the case you present with your example (same process performs underwrite and overwrite). Second is when there are no or insufficient concurrency controls in place. The second case is easily resolved simply by employing proper concurrency control mechanisms to prevent under/over writes. The first case is more sinister because normal pessimistic concurrency mechanisms won't guard against this case. This case occurs when a process holds data in memory and then updates the data in persistent storage either using direct global set/kill or by using SQL. Optimistic concurrency controls will guard against only the SQL update case, direct global set/kill will go undetected unless those set/kill actions also update the version number of the data.

%Reload() was not intended to solve this problem. %Reload() is automatically invoked when the concurrency setting of an object in memory is updated from no-retained lock (value less than 3) to a retained lock (value 3 or 4). In this case, data is automatically sync'ed with data on disk to ensure that the now-lock protected data is the same in-memory and in persistent storage. However, %Reload() can be invoked directly to perform this same action should user code somehow detect it is necessary. 

If the reason you want to %Reload() the data is because the persistent storage was modified by SQL then I have the same question as Fab asked above. Why would you use SQL to update the data? I can think of a few reasons why you might want to do that but there are other ways to accomplish the same task without having to worry about the state of data in memory vs. the state of data in persistent storage.

If you were to use optimistic concurrency controls (VERSIONPROPERTY) then %Save()/UPDATE will fail if the version numbers don't match and then the user code can go into a state where conflicts can be resolved.

There is an interesting dynamic SQL feature that will guard against the case where some objects may be in memory and the user code needs to SQL to update data. I am happy to provide an example of this technique if someone is interested.

-Dan

Another option that abstracts the caller completely from the quoting requirements is to use a parameter. Parameters in Dynamic SQL are positional. Also, keep in mind that literals are replaced automatically in dynamic SQL statements so using a parameter for this will not add any overhead to the processing.

  set statement = ##class(%SQL.Statement).%New()

  do statement.prepare("insert into Stats(Country) VALUES (?)")

  set result = statement.execute(CountryId)

Keep in mind the lowercase form of prepare and execute work as their %Prepare/%Execute counterparts but they throw exceptions instead of using %Status interfaces.

If you have flexibility with the schema definition then there are certainly other models that would make a query such as this simpler.

With an array collection that is stored as a serialized list you will have to either write a procedure, define some computed properties, or you will have to use some of the InterSystems collection extensions that may not work very well with collections of objects.

Our projection of serial types (classes that extend %SerialObject) uses a "flattening model" and we don't use that for serial collections stored as "listnode" structures. We do use it in the specific case of an array of serial objects stored using a "subnode" structure - the default.

I know this all sounds a bit scary but it doesn't need to be. When you get back to this we can walk through the options.

If the default array projection for PET.ImageStudy.Injection is used then there will be an SQL table projected from the array of objects. By default, the name of this table will be PET.ImageStudy_Injection. This projected table will define a column referencing the PET.ImageStudy table. I believe this column will be named ImageStudy. There will also be a column named Injection_RadioTracer in this table and that column will be a reference to the RadioTracer table.

If the array, Injection, in the PET.ImageStudy class is not stored using defaults then this becomes a more complex problem - still solvable but more difficult. 

Let me know if array storage defaults are used and then I can help compose a query - or perhaps you can do it with the information I provided above. You can verify this information using the System Explorer->SQL to view the table definitions.

-Dan

I should update the CSV and CSV2CLASS utility procedures to take advantage of table-valued functions. Then you could select JSON_ARRAYAGG() from CSVTVF(<arguments go here>). Of course you would have to supply the constructor for the objects, probably using JSON_OBJECT.

Have you considered using $xecute?

Version:1.0 StartHTML:00000092 EndHTML:00001371 StartFragment:00000172 EndFragment:00001337 CachÙ Studio clip   Class User.Exec [ Abstract ]
{

ClassMethod test(STATUS = 1) As %String
{
set greeting = $xecute("(STATUS) { return $S(STATUS:""HELLO"", 1:""GOODBYE"") }",STATUS)
return greeting
}

}

and here is this code in action:

PANTHER:XEP:DEV>w ##class(Exec).test()

HELLO

PANTHER:XEP:DEV>w ##class(Exec).test(0)

GOODBYE

As you have already discovered, there is no opportunity for a user to change the collection type class. That class is determined by the compiler when processing LIST and ARRAY keywords. This assignment, indicated by the compile-only keyword of RUNTIMETYPE, occurs during inheritance resolution and it cannot be overridden by the user. Your solution of coercing the RUNTIMETYPE using a method generator is not completely correct even though the runtime behavior seems correct. The problem with using the method generator is that is runs late in the compile cycle and the modification you make will not be processed by compiler actions that have already completed by this time. Your changes - simple addition of new methods - will probably work as you expect as long as those methods don't require any additional compiler processing. 

A user has only two ways to add methods to a class member - property in this case. The first and easiest is through the use of the declared type class. Internally this is cPROPtype (you have already discovered this I'm sure ;) ). Methods inherited from the datatype class (actually these are "datatype generator" classes) are combined with the property to produce the datatype implementation. These methods are typically not instance methods of the containing class but one could say they are instance methods of the generated datatype.

The second way for a user to inject methods into a class member runtime is by overriding the member super class. In the old days this was referred to as the property class but that definition is expanded to include other member types such as query, index, and so on. Methods inherited by a member from the member supertype class are typically instance methods of the containing class. For a property these methods include Get and Set. There are two keywords that a user can define - MEMBERSUPER and PROPERTYCLASS.

Both mechanisms for adding methods to a member's runtime produce what we call "composite methods". That doesn't really mean anything other than the name of the method which is composed of the member name and the inherited method name. There is an internal difference but that has little impact on runtime behavior. Composite methods look very much like normal methods but sometimes confuse users because it seems there should be a dot in the middle! For example, direct invocation of the Name property's Set method is

    do oref.NameSet(value)

This could be confusing as it seems logical to use

    do oref.Name.Set(value)

It is possible for a user to define a property super class containing method generators that will produce composite member methods.  This is not a simple process but it can be done. If this interests you then I can provide more details.

What I would recommend is an instantiable helper class. You can construct an instance of the helper class, passing in the collection instance. Methods in the helper class then operate on that instance. This is the model we use for iterators operating on instances of %Library.DynamicAbstractObject.