Presto - hex string to int

问题

I'm trying to convert hex string (starts with '0x') to it's integer value using presto. For example 0x100 to 256. My hex string is called msg_id. I tried to use this-

from_hex(substr(msg_id,3))

But I run into a problem, because from_hex expect even number of hex digits (0100 instead of 100). I decided to try and solve this using an if statement, so I tried this:

if(length(msg_id)%2=0, from_hex(substr(msg_id,3))) 

(will take care of the odd number of digits case later)

But- the result of from_hex is a varbinary type, with a varied number of bytes. I want to convert it to an Integer, or any other numeric type, but I can't find a way to do it.

Any ideas? I would appreciate it...

回答1:

You can use from_base(string, radix) to parse number written with hex digits into a bigint. You just need to strip leading '0x' first:

select from_base(substr('0x100', 3), 16);
 _col0
-------
   256

or with regexp_replace():

presto:tiny> select from_base(regexp_replace('0x100', '^0x'), 16);
 _col0
-------
   256

来源：https://stackoverflow.com/questions/50490705/presto-hex-string-to-int