Hive and regular expression

问题:

I am trying to filter all the ip adresses in a username. But this doesnt really work properly in my query:

select distinct regexp_extract(username, '^([0-9]{1,3})\.([0-9]{1,3})\.([0-9]{1,3})\.([0-9]{1,3})$', 0) from ips. 

The problem is that he even recognizes numbers as 1000000 as ip adress. Any idea how to fix it?

回答1:

You need extra backslashes to escape special characters like . or \s. There's some more info on the wiki at https://cwiki.apache.org/confluence/display/Hive/LanguageManual+UDF

Try something like:

select
    distinct regexp_extract(ip, '^([0-9]{1,3})\\.([0-9]{1,3})\\.([0-9]{1,3})\\.([0-9]{1,3})$', 0) as match
from
    ips
having
    match <> "";