Hi Developers!
Often we need to use relatively small arrays with constants, static arrays in algorithms, etc where we need to do something with each element of an array. There are several ways to deal with it in ObjectSctipt.
Previously I used to use globals, locals, PPG for this but not so long time ago figured out that %List is a way too handy.
Indeed, suppose we have an array of months and need to set up and use it in our code.
When I start talking about InterSystems IRIS with more technically-minded people I always talk about how at the root of things it is a multimodel DBMS.
In my opinion that is the main advantage (on the DBMS side).
You want some sort of summary for your data? Use SQL!
Do you want to work extensively with one record? Use objects!
Want to access or set one value and you know the key? Think again. Use globals!
And the data is stored only once. You just choose the way you want to access it.
On the first overview it's a nice story - short and concise and it gets the message across, but when people really start working with InterSystems IRIS the questions start.
How are classes and tables and globals related? What are they to each other? How's data really stored?
In this article I would try to answer these questions and explain what's really going on.
In the previous parts (1, 2) we talked about globals as trees. In this article, we will look at them as sparse arrays.
A sparse array - is a type of array where most values assume an identical value.
In practice, you will often see sparse arrays so huge that there is no point in occupying memory with identical elements. Therefore, it makes sense to organize sparse arrays in such a way that memory is not wasted on storing duplicate values.
In some programming languages, sparse arrays are part of the language - for example, in J, MATLAB. In other languages, there are special libraries that let you use them. For C++, those would be Eigen and the like.
Globals are good candidates for implementing sparse arrays for the following reasons:
In my earlier article on Adopting Bitmaps I described the technique already.
Now you can find a code example also on Open Exchange.
The Art of Mapping Globals to Classes 1 of 3
Looking to breathe new life into an old MUMPS application? Follow these steps to map your existing globals to classes and expose all that beautiful data to Objects and SQL.
It's well-known that namespace global mapping helps us to write code independent on database storage details (Caché instance name, directory path). But sometimes we can face problems accessing an unsubscripted global which has subscript level mapping (SLM) defined. Most of such cases are evident and associated with administrative tasks that should be done on database level, but some of them can confuse even an experienced developer. Just to start:
The Art of Mapping Globals to Classes (4 of 3)
The forth in the trilogy, anyone a Hitchhikers Guide to the Galaxy fan?
If you are looking to breathe new life into an old MUMPS application follow these steps to map your globals to classes and expose all that beautiful data to Objects and SQL.
If the above does not sound familiar to you please start at the beginning with the following:
The Art of Mapping Globals to Classes (3 of 3)
If you are looking to breathe new life into an old MUMPS application follow these steps to map your globals to classes and expose all that beautiful data to Objects and SQL.
If the above does not sound familiar to you please start at the beginning with the following:
Globals, these magic swords for storing data, have been around for a while, but not many people can use them efficiently or know about this super-weapon altogether.
If you use globals for tasks where they truly shine, the results may be amazing, either in terms of increased performance or dramatic simplification of the overall solution (1, 2).
Globals offer a special way of storing and processing data, which is completely different from SQL tables. They were first introduced in 1966 in the M(UMPS) programming language, which was initially used in medical databases. It is still used in the same way, but has also been adopted by some other industries where reliability and high performance are top priorities: finance, trading, etc.
Later M(UMPS) evolved into Caché ObjectScript (COS). COS was developed by InterSystems as a superset of M. The original language is still accepted by developers' community and alive in a few implementations. There are several signs of activity around the web: MUMPS Google group, Mumps User's group), effective ISO Standard, etc.
Modern global based DBMS supports transactions, journaling, replication, partitioning. It means that they can be used for building modern, reliable and fast distributed systems.
Globals do not restrict you to the boundaries of the relational model. They give you the freedom of creating data structures optimized for particular tasks. For many applications reasonable use of globals can be a real silver bullet offering speeds that developers of conventional relational applications can only dream of.
Globals as a method of storing data can be used in many modern programming languages, both high- and low-level. Therefore, this article will focus specifically on globals and not the language they once came from.
Beginning - see Part 1.
A structure, such as an ordered tree, has various special cases. Let's take a look at those that have practical value for working with globals.
The Art of Mapping Globals to Classes (2 of 3)
If you are looking to breathe new life into an old MUMPS application follow these steps to map your globals to classes and expose all that beautiful data to Objects and SQL.
This example is going to cram in 4 or 5 different things beyond what was covered in Part 1
Hi Everyone,
Link to webinar recording: https://learning.intersystems.com/course/view.php?id=623
Thank you for your interest in this webinar!
Please submit questions about the content of the webinar as comments below this article.
In the prior part of this series we have provided introduction to Google MapReduce approach, but still not covered their possible ObjectScript implementation. Which we will start to explain today.
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:
Now, let’s say you can’t access the terminal or simply you just rather execute it from a web interface. In this article, I will show you how to execute terminal commands from a simple web page.
For example, in the image below you see how we execute $zv on a webpage:
NewBie's Corner Session 27 Traversing A Global with $Order Part 1
Welcome to NewBie's Corner, a weekly or biweekly post covering basic Caché Material.
Traversing A Global
Perhaps the most difficult concept in Caché/MUMPS is its Global Structure. This session and several that follow it deals with the Global Structure. However, just presenting the material will not guarantee your understanding of it. You must experiment with the data and concepts that are presented.
We're developing Ensemble PoC and one day our frontend developer (who doesn't have Ensemble production running) said that Populate just doesn't cut it and he needs to see the real data. He needed only one object, but the problem was - it's a big object. Still, I checked ids of everything related and wrote this command (parts omitted, but you get the idea):
Process-private Globals can be used as a data global in storage definition. That way, each process can have its own objects for the class with ppg storage. For example lets define a pool, which can:
Here's the class:
Order is a necessity for everyone, but not everyone understands it in the same way
(Fausto Cercignani)
Disclaimer: This article uses Russian language and Cyrillic alphabet as examples, but is relevant for anyone who uses Caché in a non-English locale.
Please note that this article refers mostly to NLS collations, which are different than SQL collations. SQL collations (such as SQLUPPER, SQLSTRING, EXACT which means no collation, TRUNCATE, etc.) are actual functions that are explicitly applied to some values, and whose results are sometimes explicitly stored in the global subscripts. When stored in subscripts, these values would naturally follow the NLS collation in effect (“SQL and NLS Collations”).
If you are waiting for the Kindle Edition of Caché and MUMPS – Part II, I must apologize. I believed what others told me that once I have a book manuscript, the Kindle manuscript will be easy. Being a programmer I should have remembered: "never assume anything." The conversion to Kindle is proving a much bigger task than I thought. But don't lose heart, I am working full time on it. I have as my goal before May 1st. But, then again, you know what they say about goals. ;) - - Paul Mike Kadow
