Overhead calling UDF in Sql server 2005

Posted on One min read

Today I found a performance issue in a project of mine, after some try, I found that the overhead of calling a udf function is really enormous…I have a query that move data from a table to another, it move about 25.000 rows, and one of the field of original table is transformed with a UDF. The query without udf runs in about 1500 ms, the query that calls udf runs in 180 minutes, even if in the UDF I simply return the parameter and do no calculation at all. Then I come across this post that deals about this issues….so the rule is, do not use udf if you know that the udf will be called for thousands rows.

Alk.