Random Digit Data Masking on Id_number in Vertica - sql

Question

I need to mask 4 digit of id_number rondomly between 6th and 12th digits.
Example:
555444888777 --> 55544x8x8xx7
I wrote following code but it is rondom for every 2 digit. Is there any solution for rondomly masking with given intervals and how many digits for needed to mask in Vertica ?
SELECT OVERLAYB(OVERLAYB(OVERLAYB(OVERLAYB('555444888777', 'x', 5+RANDOMINT(2)),'x', 7+RANDOMINT(2)),'x', 9+RANDOMINT(2)),'x',11+RANDOMINT(2));

Answer 1

If you really want to randomly replace a digit with an 'x' at , randomly, the first or second digit after positions 5,7,9 and 11, as you coded it, then create a function as I did, so you don't need to re-code the nested OVERLAYB() calls every time.
You can replace 5,7,9 and 11 with a RANDOMINT() call, too, if you want more variance.
If, however, you want to vary the number of replacements (from 4 times to another number of times), you will have to re-write the function for a different number of replacements. Or go through the trouble of writing a UDx (User Defined Extension), in C++, Java, R or Python.
Check the Vertica docu for that; start here:
https://www.vertica.com/docs/10.0.x/HTML/Content/Authoring/SQLReferenceManual/Statements/CREATEFUNCTIONUDF.htm?zoom_highlight=create%20function
Having said that, here goes the function with your same functionality, and its test:
CREATE OR REPLACE FUNCTION maskrand(
s VARCHAR(256)
)
RETURN VARCHAR(256)
AS
BEGIN
RETURN (
OVERLAYB(
OVERLAYB(
OVERLAYB(
OVERLAYB(
s
, 'x'
, 5+RANDOMINT(2)
)
,'x'
, 7+RANDOMINT(2)
)
,'x'
, 9+RANDOMINT(2)
)
,'x'
, 11+RANDOMINT(2)
)
);
END;
-- test ...
WITH indata(s) AS (
SELECT '555444888777'
UNION ALL SELECT '666333444888'
)
SELECT
s, maskrand(s) AS masked
FROM indata;
-- out s | masked
-- out --------------+--------------
-- out 555444888777 | 5554x48x8xx7
-- out 666333444888 | 6663x3x4x88x

Answer 2

This is a bit crazy, but seems to work:
with my_range as (
select 6 as n
union all select 7 as n
union all select 8 as n
union all select 9 as n
union all select 10 as n
union all select 11 as n
union all select 12 as n),
random_positions as (
select n
from my_range
order by random()
limit 4),
quartiles as (
select n,
ntile(4) over(order by n) as quartile
from random_positions),
sorted_positions as (
select max(case when quartile = 1 then n end) as random1,
max(case when quartile = 2 then n end) as random2,
max(case when quartile = 3 then n end) as random3,
max(case when quartile = 4 then n end) as random4
from quartiles)
select '555444888777' as string_original,
overlay(
overlay(
overlay(
overlay('555444888777' placing 'x' from random1)
placing 'x' from random2)
placing 'x' from random3)
placing 'x' from random4)
as string_masked
from sorted_positions;
Sample executions:
$ vsql -f tmp.sql
string_original | string_masked
-----------------+---------------
555444888777 | 55544xx8xx77
(1 row)
$ vsql -f tmp.sql
string_original | string_masked
-----------------+---------------
555444888777 | 55544xx8x7x7
(1 row)
$ vsql -f tmp.sql
string_original | string_masked
-----------------+---------------
555444888777 | 55544x8x8x7x
(1 row)
Explanation:
my_range builds a recordset with numbers from 6 to 12
random_positions sorts the recordset randomly, only returning 4 positions
quartiles assigns the quartile to each random position so sorted_positions can pivot the results into a single record
finally, the last select applies the OVERLAY function four times at the four random positions