Can I perform stats count on a substring using regex?

[chetan1974]

I have log events such as activity:http://xyz/rest/876
http://xyz/rest/223
http://xyz/rest/263
http://xyz/rest/4534
http://abc/rest/1
when I do stats count by activity I want to get results as:
http://xyz/rest 4
http://abc/rest 1

How can it be best done?

[DalJeanis · Accepted solution]

Try this:

|  rex "(?<activity>http:\/\/[^\/]*\/rest)" 
| stats count as mycount by activity