#Object Data Model

Hello!

This article is a small overview of a tool that helps to understand classes and their structure inside the InterSystems products: from IRIS to Caché, Ensemble, HealthShare.

In short, it visualizes a class or an entire package, shows the relations between classes and provides all the possible information to developers and team leads without making them go to Studio and examine the code there.

If you are learning InterSystems products, reviewing projects a lot or just interested in something new in InterSystems Technology solutions — you are more than welcome to read the overview of ObjectScript Class Explorer!

Class Queries in InterSystems IRIS (and Cache, Ensemble, HealthShare) is a useful tool that separates SQL queries from Object Script code. Basically, it works like this: suppose that you want to use the same SQL query with different arguments in several different places.In this case you can avoid code duplication by declaring the query body as a class query and then calling this query by name. This approach is also convenient for custom queries, in which the task of obtaining the next row is defined by a developer. Sounds interesting? Then read on!

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.,

Before we start talking about databases and different data models that exist, first we'd better talk about what a database is and how to use it.

A database is an organized collection of data stored and accessed electronically. It is used to store and retrieve structured, semi-structured, or raw data which is often related to a theme or activity.

At the heart of every database lies at least one model used to describe its data. And depending on the model it is based on, a database may have slightly different characteristics and store different types of data.

To write, retrieve, modify, sort, transform or print the information from the database, a software called Database Management System (DBMS) is used.

The size, capacity, and performance of databases and their respective DBMS have increased by several orders of magnitude. It has been made possible by technological advances in various areas, such as processors, computer memory, computer storage, and computer networks. In general, the development of database technology can be divided into four generations based on the data models or structure: navigational, relational, object and post-relational.

You probably have a similar experience.
The more I use Atelier the more I miss INSPECTOR that I had in Studio!

First for PROPERTIES that can inherit a variable number of Parameters beyond imagination.
take %XML.Adapter as the most obvious.
next:
Where to find all inherited methods that I eventually want to overload? Take %Persistent as example.

Or where or how can %OnBeforeAddToSaveSet() (the correct camel case) be overloaded ?

Introduction

The common requirement in many applications is logging of data changes in a database - which data has changed, who changed them and when (audit logging). There are many articles about this question and there are different approaches on how to do that in Caché.

Setting the Scene

I was editing the properties of a persistent ObjectScript class the other day and noticed that the storage definition wasn't updating to reflect my latest changes.

In this case, I deleted a property that was no longer needed from the class definition, saved, recompiled, and still saw it in the storage definition.

This post is the direct result of working with an InterSystems customer who came to me with the following problem:

SELECT COUNT(*) FROM MyCustomTable

Takes 0.005 seconds, total 2300 rows. However:

This is a sample to use %JSON.Adaptor class available in IRIS to produce a snapshot of your object.

The sample consists of 2 classes that are variations of what was known in Caché/SAMPLES as Sample.Person.
Be aware that the possibilities are limited by %JSON.Adapter and how you make use of it.

Once in place, you create some test data by Populate().
You select an object and take a snapshot.
You apply changes to your object and take another snapshot.
And see the difference.

BINGO!

@Ming Zhou asked a great question in https://community.intersystems.com/post/how-get-all-properties-defined-c... and the answer sums up exactly why ObjectScript is my favorite.

A concurrent session in IRIS:
SQL, Objects, REST, and GraphQL

Kazimir Malevich, "Athletes" (1932)

"But of course you don't understand! How can a person who has always traveled in a horse-drawn carriage understand the feelings and impressions of the express traveler or the pilot in the air?"

Kazimir Malevich (1916)

Introduction

We’ve already addressed the topic of why object/type representation is superior to SQL for implementing subject area models. And those conclusions and facts are as true now as they have ever been. So why should we take a step back and discuss technologies that drag abstractions back to the global level, where they had been in the pre-object and pre-type era? Why should we encourage the use of spaghetti code, which results in bugs that are hard to track down, and which relies only on virtuoso developer skills?

There are several arguments in favor of transmitting data via SQL/REST/GraphQL-based APIs as opposed to representing them as types/objects:

What if you could serialize/deserialize objects in whatever format: JSON, XML, CSV,...; attending different criteria: export/import some properties and not others, transform values in this or that way before exporting/importing,...; and all of this without having to change the class definition? Wouldn't that be great??

Well, perhaps it's a goal too ambitious to reach 100% but, exploring this idea, I've developed a bunch of classes that I thought it was good to share. If you want to test, change, modify or improve the code, or just take a look at it, you can do it here. There you'll find a more detailed explanation (see Readme.md)

For each defined property, query or an index, several corresponding methods would be automatically generated on a class compilation. These methods can be very useful. In this article, I would describe some of them.

Hi!

It is often necessary to run some external command such as a python program or a shell script from inside Caché/Ensemble. There are three ways of doing this: