I have a set of databases that resides on the local SQL server 2014 instances of my clients. I recently made some modifications to the databases which seem innocent in nature (added a few columns, changed some data, nothing out of the ordinary). My process is pretty simple, for each database, I do the following:
- DBCC CheckDB
- Add columns, change some data, whatever simple stuff
- For each table in the database, ALTER INDEX ALL ON Table_Name REBUILD
But now, queries that use to take only milliseconds are taking seconds. That's a performance degradation by a factor of 1000! But here's where it gets weird: this radical performance degradation only happens at the clients' sites. If I detach the databases, bring them over to my workstation (which is an older system than my clients'), all queries run lightning fast!!!
What could be the issue? What should I investigate and how? I tried restarting the clients' systems, no effect. They all seem to have plenty of available memory and the SQL Server instance eats up its usual fair share.
I'm at my wits end so any help would be dearly appreciated!
Thanks for reading!