Question
· Aug 31

How exactly does the OperationLimit Property on the Regex-Matcher work, and how do I get it to work?

Hi there,

I want to use regex in my code, and I saw that the %Regex.Matcher class contains a property "OperationLimit" that you can also set to a number of steps that the regex engine should take maximum in analysing a given string. So far so good.

I tried to set the property with the function OperationLimitSet() to a silly value like 3. In 3 steps only very few regex should be executed, right? But what I found is that my regex always comes up with a solution. Here is what I did:

 

First I initialised my %Regex.Matcher.

set m = ##class(%Regex.Matcher).%New("(.+)\@(.+)\.(.+)")
do m.OperationLimitSet(3)
do m.TextSet("thisismytest@email.com")

 

Then I ran the regex and found my 3 groups.

zw m.Locate()
1
zw m.Group(1)
"thisismytest"
zw m.Group(2)
"email"
zw m.Group(3)
"com"

 

Now maybe I have completely misunderstood the OperationLimit property, or my implementation of this simple regex matcher is faulty, but the documentation clearly states: "Setting OperationLimit to a positive integer will cause a match operation to signal a TimeOut error after the specified number of clusters of steps by the match engine".  As I am using the Locate() function and not the Match() function, I wondered if the documentation specifically talks about the Match() function. But both the Locate() and Match() function execute without any problem.

set m = ##class(%Regex.Matcher).%New("(.+)\@(.+)\.(.+)")
do m.OperationLimitSet(3)
do m.TextSet("thisismytest@email.com")

zw m.Match()
1

I would appreciate any input as to why my regex is still running perfectly and what I can do to prevent this, as I would obviously like to set a realistic OperationLimit of 4000 or something in that range in the future.

Thanks for your help!

Product version: IRIS 2021.1
$ZV: IRIS for Windows (x86-64) 2021.1.2 (Build 338_0_22215U) Fri Feb 17 2023 18:29:06 EST
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