#Code Snippet

Date range queries going too slow for you? SQL Performance got you down? I have one weird trick that might just help you out! (SQL Developers hate this!)*

If you have a class that records timestamps when the data is added, then that data will be in sequence with your IDKEY values - that is, TimeStamp₁ < TimeStamp₂ if and only if ID₁ < ID₂ for all IDs and TimeStamp values in table - then you can use this knowledge to increase performance for queries against TimeStamp ranges. Consider the following table:

The topic of for/while loop performance in Caché ObjectScript came up in discussion recently, and I'd like to share some thoughts/best practices with the rest of the community. While this is a basic topic in itself, it's easy to overlook the performance implications of otherwise-reasonable approaches.

Hi!

I believe the simplest is (to work with csv delimited by ";"):

set file = ##class(%File).%New( "data.csv" )
    set sc = file.Open( "R" ) 
    if $$$ISERR(sc) quit    ; or do smth

    while 'file.AtEnd {
        set str=file.ReadLine() 
        for i=1:1:$length( str, ";" ) {
            set id=$piece( str, ";" ,i ) 
            write !, id  // or do smth
        }
    }
    do file.Close()

Possible options:

different variants of error handling with sc code.

Embrace while loop into try/catch block.

And what's yours?

Question:

How do I get a list of files residing in a certain folder/directory, according to some wildcard/filter.

For example all '*.txt' files in 'C:\Temp'.

Answer:

In CACHE –

You can use the %Library.File's FileSet class query.

Here's some sample code using it (also attached):

Two fairly common requests we receive from HL7 customers are (1) how to remove all trailing delimiters for fields and segments in HL7 messages and (2) how to "find and replace" for an entire HL7 message (as opposed to one segment/field at a time). The code sample below shows a custom function that solves for item 1 and by extension item 2 above. In other words the same approach can be used for finding/replacing any sequence of chars in an entire HL7 message, with some tweaks to the custom function.

Is there a better way to iterate through all properties of an object than the following? Perhaps without needing to open a definition of the class but directly against the object?

Checking if Directory or File Exists:

Outlined below is an example of how to check if a directory exists:

Set directoryName="c:\temp\nosuchdir"

/* Check for existence of a directory - Return Value:  0 - directory does not exist;  1 - directory does exist  */

Set directoryExists=##class(%File).DirectoryExists(directoryName)

If ('directoryExists)  // do the processing for when a directory does not exist

Outlined below is an example of how to check if a file exists:

Hi, Community!

Have a question for general discussion.

In ObjectScript we have cls for classes and mac code, which both compile into int code.

Is there any reason when you use mac instead of cls for non-persistent classes?

For me the benefits for cls are:

1. Inheritance and other OOP features

2. Auto-documented code

For mac one visible benefit is easier call in terminal:

do method^Utils(p1,p2)

vs

There have been a few use cases recently within InterSystems where we've needed to connect to Caché-based web services from PHP. The first of these was actually the Developer Community itself, which uses web services as part of Single Sign-On with other InterSystems sites/applications. The following example demonstrates how to connect to a Caché-based web service (particularly, the web service in the SAMPLES namespace) from PHP, using password authentication.

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:

DTL Transformations and GetValueAt/SetValueAt calls on HL7 messages will truncate any fields longer than 32K. To avoid this, the methods GetFieldStreamRaw and StoreFieldStreamRaw must be used when dealing with fields that might be larger than 32K. OBX:5 is a frequent example. These methods have some subtleties and must be used carefully.

This can't be done by simply dragging from left to right in a DTL. It must be done with a code action. Also, the StoreFieldStreamRaw call must be the last edit made to the segment because the segment becomes immutable after that.

I believe the I have followed the instructions to attach a document to the body of a post request but nothing is being sent out in the files{} port of the request. I can either get the stream in "data", not visible at all, or visible but no form data. Any help would be appreciated, below is what I have:

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)

Hi Community!

Coding guidelines discussion. Consider you have For with one command in the cycle. Here are the options:

One

For i=1:1:1000 set ^Test(i)=""

Two

For i=1:1:1000 {
 set ^Test(i)=""
}

Same for the "If":

if a set b=a

or

if a {
 set b=a
}

Your choice? Or maybe even other options?