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#Object Data Model

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An object data model is that data or code is composed of modules that combine data and procedures that work on the data.

Learn more.

Here's one way to determine if a class is mapped (i.e. it is in a package whose definitions come from a database other than the default code database for the current namespace):

SAMPLES>w ##class(%Library.RoutineMgr).IsMapped("Cinema.Film.cls")
0
SAMPLES>w ##class(%Library.RoutineMgr).IsMapped("%iKnow.Objects.Source.cls")
1
SAMPLES>

If you pass a by-ref second argument to IsMapped you can also discover what database the class definition is stored in:

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Question
· Aug 10, 2017
LogicalToDisplay Method

Hi, I am trying to understand the transformational methods.

  • LogicalToDisplay()
  • LogicalToOdbc()
  • OdbcToLogical()
  • DisplayToDisplay()

I have created a small class with the only property of List as %List, see below.

Class LastName.Demo2 Extends %Persistent
{
Property List As %List;

}

Then I entered the following commands in the Terminal

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Question
· Aug 9, 2017
%Library.Char

The data type %Char or %Library.Char

The description says it is a fixed length character field.

How do I set the fixed length?

Or by just setting %Char to something, does that automatically define its length?

Are the parameters MINLEN, MAXLEN involved? Or are these the way I set the fixed length?

Any help with this?

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Article
· Aug 8, 2017 1m read
Outperforming PostgreSQL and MySQL

In a previous exercise, I was able to show the power of Caché.
A medium-designed set of interdependent tables with some GB of data.
URLs cross reference over some million pages resulting in ~3 billion records

Competition was between

  • Caché
  • PostgreSQL
  • MySQL

Criteria were Speed + Storage consumption
I composed a customized loader fed over a "raw" TCP connection
Mapping the "objects" into the final table by directly writing to Global Storage.,

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Have very little XML experience and have been able to manually create output. Have a need to take data that I store in a M global (example: ^TML("HDATA", ) and out put it in CCDA XML format.

Are there any examples of M code using the XMLWriter to accomplish this?

Or can anyone provide some guidance

Any help would be greatly appreciated.

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Hi everyone

Is there any way to change a class definition (especifically a query definition during the compilation time)?
The idea is:
I have an abstract class with a parameter where I will define the ROWSPEC of a query and some methods to populate e temporary table
The implementation class will override the parameter, specifying the ROWSPEC of this implementation, and the methods will populate the rows in the same format as the ROWSPEC.

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Question
· Jul 16, 2017
How to index a class

Hi

I have two persistent classes defined. Lets call it Parent and Child.

Child class is one of the property of Parent Class.

I would like to define a index on Child class.

So what is the default behaviour I defined a index on a non simple data type member?

Any possibility that I could customized the behaviour ? For example. Child class has three properties.

Could I configure the index to index any combinations of these three properties?

Thanks for your help.

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I am working with Caché Relationships.

I know how to iterate through the One side of the relationship and for each One iterate through all the various Manys.

What I have been trying to figure out, is the code (I can put into a Class) that will start at the top of the Manys, iterate down and for each of the Manys, pull the associated One.

I can do this with SQL or Globals, but I want to use only Class type code.

Is that clear? Any help?

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You might find it useful or not. It depends on what you can imagine it to be used with, like I had to.

Either way, I created a lib that can fetch environment variables from a file or from the OS where Caché is running.

Mostly know as dotenv. Many languages have it, so why not Caché?

The usage is pretty simple:

If you want to use OS env vars exclusively, just use the method:

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Article
· Jul 7, 2017 19m read
Indexing of non-atomic attributes

Quotes (1NF/2NF/3NF)ru:

Every row-and-column intersection contains exactly one value from the applicable domain (and nothing else).
The same value can be atomic or non-atomic depending on the purpose of this value. For example, “4286” can be
  • atomic, if its denotes “a credit card’s PIN code” (if it’s broken down or reshuffled, it is of no use any longer)
  • non-atomic, if it’s just a “sequence of numbers” (the value still makes sense if broken down into several parts or reshuffled)

This article explores the standard methods of increasing the performance of SQL queries involving the following types of fields: string, date, simple list (in the $LB format), "list of <...>" and "array of <...>".

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This is a translation of the following article. Thanks [@Evgeny Shvarov] for the help in translation.

This post is also available on Habrahabrru.

The post was inspired by this Habrahabr article: Interval-associative arrayru→en.

Since the original implementation relies on Python slices, the Caché public may find the following article useful: Everything you wanted to know about slicesru→en.

Note: Please note that the exact functional equivalent of Python slices has never been implemented in Caché, since this functionality has never been required.

And, of course, some theory: Interval treeru→en.

All right, let’s cut to the chase and take a look at some examples.

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It is possible to update Cache object property from Python using the following Python code, with import of intersys.pythonbind3:

my_object.set("my_property",["A","B","C"])

However, I am unable to save 2D %List with 2D Python array like the following:

my_object.set("my_property",[["A","B","C"],["1","2","3"]])

I am not sure whether this is Python-Cache bind flaw or design issue. Is there any alternative/ workaround to do the same for above?

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