PostgreSQL Varchar UID to Int UID while preserving uniqueness - sql

Question

Say I have a unique column of VarChar(32).
ex. 13bfa574e23848b68f1b7b5ff6d794e1.
I want to preserve the uniqueness of this while converting the column to int. I figure I can convert all of the letters to their ascii equivalent, while retaining the numbers and character position. To do this, I will use the translate function.
psuedo code: select translate(uid, '[^0-9]', ascii('[^0-9]'))
My issue is finding all of the letters in the VarChar column originally.
I've tried
select uid, substring(uid from '[^0-9]') from test_table;
But it only returns the first letter it encounters. Using the above example, I would be looking for bfaebfbbffde
Any help is appreciated!

Answer 1

First off, I agree with the two commenters who said you should use a UID datatype.
That aside...
Your UID looks like a traditional one, in that it's not alphanumeric, it's hex. If this is the case, you can convert the hex to the numeric value using this solution:
PostgreSQL: convert hex string of a very large number to a NUMERIC
Notice the accepted solution (mine, shame) is not as good as the other solution listed, as mine will not work for hex values this large.
That said, yikes, what a huge number. Holy smokes.
Depending on how many records are in your table and the frequency of insert/update, I would consider a radically different approach. In a nutshell, I would create another column to store your numeric ID whose value would be determined by a sequence.
If you really want to make it bulletproof, you can also create a cross-reference table to store the relationships that would
Reuse an ID if it ever repeated (I know UIDs don't, but this would cover cases where a record is deleted by mistake, re-appears, and you want to retain the original id)
If UIDs repeat (like this is a child table with multiple records per UID), it would cover that case as well
If neither of these apply, you could dumb it down quite a bit.
The solution would look something like this:
Add an ID column that will be your numeric equivalent to the UID:
alter table test_table
add column id bigint
Create a sequence:
CREATE SEQUENCE test_id
create a cross-reference table (again, not necessary for the dumbed down version):
create table test_id_xref (
uid varchar(32) not null,
id bigint not null,
constraint test_id_xref_pk primary key (uid)
)
Then do a one-time update to assign a surrogate ID to each UID for both the cross-reference and actual tables:
insert into test_id_xref
with uids as (
select distinct uid
from test_table
)
select uid, nextval ('test_id')
from uids;
update test_table tt
set id = x.id
from test_id_xref x
where tt.uid = x.uid;
And finally, for all future inserts, create a trigger to assign the next value:
CREATE OR REPLACE FUNCTION test_table_insert_trigger()
RETURNS trigger AS
$BODY$
BEGIN
select t.id
from test_id_xref t
into NEW.id
where t.uid = NEW.uid;
if NEW.id is null then
NEW.id := nextval('test_id');
insert into test_id_xref values (NEW.uid, NEW.id);
end if;
return NEW;
END;
$BODY$
LANGUAGE plpgsql VOLATILE
COST 100;
CREATE TRIGGER insert_test_table_trigger
BEFORE INSERT
ON test_table
FOR EACH ROW
EXECUTE PROCEDURE test_table_insert_trigger();

Answer 2

create one function which replace charter with blank which you not need in string,
CREATE FUNCTION replace_char(v_string VARCHAR(32) CHARSET utf8) RETURNS VARCHAR(32)
DETERMINISTIC
BEGIN
DECLARE v_return_string VARCHAR(32) DEFAULT '';
DECLARE v_remove_char VARCHAR(200) DEFAULT '1,2,3,4,5,6,7,8,9,0';
DECLARE v_length, j INT(3) DEFAULT 0;
SET v_length = LENGTH(v_string);
WHILE(j < v_length) DO
IF ( FIND_IN_SET( SUBSTR(v_string, (j+1), 1), v_remove_char ) = 0) THEN
SET v_return_string = CONCAT(v_return_string, SUBSTR(v_string, (j+1), 1) );
END IF;
SET j = j+1;
END WHILE;
RETURN v_return_string;
END$$
DELIMITER ;
Now you just nee to call this function in query
select uid, replace_char(uid) from test_table;
It will give you string what you need (bfaebfbbffde)
If you want to int number only i.e 13574238486817567941 then change value of variable, and also column datatype in decimal(50,0), decimal can stored large number and there is 0 decimal point so it will store int value as decimal.
v_remove_char = 'a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z';