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:

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This article will describe and include an example of how to embed an external PDF file into an HL7 segment, specifically ADT_A01:2.3.1 OBX(). This can be useful when attempting to insert pictures or other external data into an HL7 message. In this example, the name of the PDF file to be embedded is provided in the incoming HL7 message in OBX(1):ObservationValue field.

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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.

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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?

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Article
Tani Frankel · Feb 17, 2016 3m read
Listing files in folder

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):

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I'm aware of two ways to get list of files in a dir:

set dir = "C:\temp\"
set rs = ##class(%File).FileSetFunc(dir, , , 1)
do rs.%Display()

and:

set dir = "C:\temp\"
set file=$ZSEARCH(dir_"*")
while file'="" {
   write !,file
   set file=$ZSEARCH("")
}

Yet they bot return only files and directories in a current directory, but not files in subdirectories.

I suppose I call one of these recursively, but maybe there's a better solution?

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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.

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Hi!

Want to share with you code snippet of try catch block I usually use in methods which should return %Status.


{ 
 try {
  	$$$TOE(sc,StatusMethod())
 }
 catch e {
 	set sc=e.AsStatus()
 	do e.Log()
 }

Quit sc 
}

Here $$$TOE is a short form of $$$TROWONERROR macro.

Inside macro StatusMethod is any method you call which will return %Status value. This value will be placed into sc variable.

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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

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With the release of Cache 2016.1, JSON support was re-architected and made part of the core object model with the creation of %Object and %Array classes, which allow you to create dynamic JSON enabled objects and arrays.

On a recent demonstration I was working on, I had the need to create a REST web service that returned a JSON representation of a persistent object. After searching for methods that would allow me to accomplish this, ultimately I found none, until now.

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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.

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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:

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Cache tricks

Several years ago, long before Developer Community Portal was launched, I published a series of Caché tricks at one of Czech web sites. In this article, I’m posting translated version of one of them.

Capturing output of someone else’s methods or routines

Suppose you, or someone else created a useful method or routine, that was producing some computation that you’d like to benefit from, but the routine was writing output to process principal device.

You would like to use the data, but you need it not written to a device, but assigned to a variable. And, for any reason, you can’t modify the code. What can you do?

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Article
Pravin Barton · Mar 28, 2019 2m read
ObjectScript error handling snippets

ObjectScript has at least three ways of handling errors (status codes, exceptions, SQLCODE, etc.). Most of the system code uses statuses but exceptions are easier to handle for a number of reasons. Working with legacy code you spend some time translating between the different techniques. I use these snippets a lot for reference. Hopefully they're useful to others as well.

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Article
Lexi Hayden · Jul 18, 2017 2m read
Old/New Dynamic SQL Cheat Sheet

The newer dynamic SQL classes (%SQL.Statement and %StatementResult) perform better than %ResultSet, but I did not adopt them for some time because I had learned how to use %ResultSet. Finally, I made a cheat sheet, which I find useful when writing new code or rewriting old code. I thought other people might find it useful.

First, here is a somewhat more verbose adaptation of my cheat sheet:

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EnsLib.HL7.Message.cls provides many API methods for manipulating an HL7 message. RemoveSegmentAt(), for example, can be used to remove a segment by path or index, but only one segment at a time. There may be times that you'll need to remove all segments within a group or even many groups of segments from the HL7 message. Surely you can iterate through each segment in each group and remove them one by one, but there's a much easier way.

With just one command, like below, you can remove all OBX segments in an ORU_R01 message (msg):

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to dismount/mount a database, use Dismount() and Mount() methods in SYS.Database class available in %SYS namespace.
NB: the database ID is its Directory

You'll find some examples of how to dismount/mount and check if a database is mounted (Mounted=1) or not (Mounted=0), and quickly see all the attributes of a database (via zwrite)

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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.

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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)

Be aware, this is a proof of concept for myself done in spare times, sure it's not robust enough or it can be done much better... but, I was just playing...ok, I could just wait to the new JSON Adaptor (coming soon!) that sure is going to resolve much more scenarios in a cleaner way, but... meanwhile... :-) ...

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