使用SQL Server扩展属性的性能注意事项

Question

To All,

We are wanting to use Extended Properties as part of our database documentation. One of my co-workers mentioned that on a prior project they used Extended Properties and it impacted database performance.

I have been searching the internet for any corroborating information in regard to this. I've not found anything.

Has anyone encountered this? If so, is there an article or link where I can read up on this?

Thanks - Mr. Do

Note: this is a SQL Server 2005 database.

Answer 1

Your colegue is wrong. There is no performance impact on normal database operations if you use extended properties.

The only impact extendet properties have is on operations that read or write extended properties . This impact depends on the way properties are read and set, and the size and number of properties.

Answer 2

They are simply text properties: not considered in plans, compiling, statistics, anything.

Unless you do some painful/fancy "SELECT * FROM sys.extended_properties " stuff...

They are also very useful to document and add comments to the database objects: especially in conjunction with 3rd party tools like Red Gate SQL Doc (may be others)

Answer 3

The only thing I've seen is that when I am updating them, I am sometimes affected by locks already on the object when particular processes are running, but performance is not a reason to avoid using them.

FYI: I noticed that extended properties disappear on UDFs when a UDF is altered to remove schemabinding and then re-add schemabinding.