I don’t often go down code based rabbit holes, its just not what I do day to day but a while back, someone asked on twitter’s #sqlhelp hashtag if there was a character length limit to the STUFF function. The documentation didn’t have an answer. For that reason only, I decided to take a look. By some coincidence this month on behalf of T-SQL Tuesday, Reitse Eskens (b|t) asks:
“What are your most fun script, procedures or statements that you’ve written”
So, I thought I’d share my code. Spoiler alert I ran it up to 50 million characters on my laptop and it kept working but it started to take a long time (4H, 28 minutes). Going up to these limits is not your day to day typical use of the function, it’s quite unusual and not really a production scenario. I’m not sure this code serves any useful purpose but by sharing, it saves it sitting smugly in my “SillyStuff” folder doing nothing.
What is the point of the STUFF function
There’s no point in me paraphrasing, here is Microsoft’s own explanation: The STUFF function inserts a string into another string. It deletes a specified length of characters in the first string at the start position and then inserts the second string into the first string at the start position.
So in my example where I am trying to stuff text into 50 million character long strings, it’s a mostly pointless exercise in terms of reality. A good use case might include obfuscating something sensitive like PII data, formatting dates and times with non standard characters or simply inserting a string at a specific place within another string.
The Code
/* This came about after @PamelaMooney tweeted: #SQLHelp Is anyone aware of a character length on the STUFF function? I still don't have a definitive answer but I can get it working up to 50 million characters. If you are stuffing beyond that, good luck to you. */ DECLARE @var NVARCHAR(MAX) = N'' DECLARE @counter int = 0 WHILE @counter < 200001 BEGIN SET @var += '500 characters pqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuv500 characters pqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuv500 characters pqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuv500 characters pqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuv500 characters pqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuv' SET @counter +=1 END SELECT STUFF(@var, 5, 1, ' Still works! ') SELECT LEN(@var)
I’m going to leave it there for now, its a waste of CPU cycles if I keep trying to break it. If anyone wants to push this to the limit, please feel free to let me know the results in the comments. I hope it was a fun read, back when I hosted T-SQL Tuesday, I asked about snippets of useful code. Although this is not so useful, it’s the type of topic I like to see offered.
