Globals

In my earlier article on Adopting Bitmaps I described the technique already.
Now you can find a code example also on Open Exchange.

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 (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:

The Art of Mapping Globals 1

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.

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 

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:

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.

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:

• add elements to a pool (ignoring duplicates)
• check if an element exists in the pool

Here's the class: