MySQL: bulk updating in table - mysql

Question

I'm using MySQL 5.6 and I have this issue.
I'm trying to improve my bulk update strategy for this case.
I have a table, called reserved_ids, provided by an external company, to assign unique IDs to its invoices. There is no other way to make this; I can't use auto_increment fields or simulated sequences.
I have this PL pseudocode to make this assignment:
START TRANSACTION;
OPEN invoice_cursor;
read_loop: LOOP
FETCH invoice_cursor INTO internalID;
IF done THEN
LEAVE read_loop;
END IF;
SELECT MIN(SECUENCIAL)
INTO v_secuencial
FROM RESERVED_IDS
WHERE COUNTRY_CODE = p_country_id AND INVOICE_TYPE = p_invoice_type;
DELETE FROM RESERVED_IDS WHERE SECUENCIAL = v_secuencial;
UPDATE MY_INVOICE SET RESERVED_ID = v_secuencial WHERE INVOICE_ID = internalID;
END LOOP read_loop;
CLOSE invoice_cursor;
COMMIT;
So, it's take one - remove - assign, then take next - remove - assign... and so on.
This works, but it's very very slow.
I don't know if there is any approach to make this assignment in a faster way.
I'm looking for something like INSERT INTO SELECT..., but with UPDATE statement, to assign 1000 or 2000 IDs directly, and no one by one.
Please, any suggestion is very helpful for me.
Thanks a lot.
EDIT 1: I have added WHERE clause details, because it was requested by user #vmachan . In the UPDATE...INVOICE clause, I don't filter by other criteria, because I have the direct and indexed invoice ID, which I want to update. Thanks

Answer 1

Finally, I have this solution. It's much faster than my initial approach.
The UPDATE query is
set #a=0;
set #b=0;
UPDATE MY_INVOICE
INNER JOIN
(
select
F.invoice_id,
I.secuencial as RESERVED_ID,
CONCAT_WS(/* format your final invoice ID */) AS FINAL_MY_INVOICE_NUMBER
FROM
(
select if(#a, #a:=#a+1, #a:=1) as current_row, internal_id
from MY_INVOICE
where reserved_id is null
order by internal_id asc
limit 2000
) F
INNER JOIN
(
SELECT if(#b, #b:=#b+1, #b:=1) as current_row, secuencial
from reserved_ids
order by secuencial asc
limit 2000
) I USING (CURRENT_ROW)
) TEMP MY_INVOICE.internal_id=TEMP.INTERNAL_ID
SET MY_INVOICE.RESERVED_ID = TEMP.RESERVED_ID, MY_INVOICE.FINAL_MY_INVOICE_NUMBER=TEMP.FINAL_MY_INVOICE_NUMBER
So, with autogenerated and correlated secuencial numbers #a and #b, we can join two different and no related tables like MY_INVOICE and RESERVED_IDs.
If you want to check this solution, please execute this tricky update following these steps:
Execute #a and then the first inner select in an isolated way: select if(#a, #a:=#a+1, ...
Execute #b and then the second inner select in an isolated way: select if(#b, #b:=#b+1, ...
Execute #a, #b and the big select that builds the TEMP auxiliar table: select F.invoice_id, ...
Execute the UPDATE
Finally, remove the assigned IDs from RESERVED_ID table.
Assignation time reduced drastically. My initial solution was one by one; with this, you assign 2000 (or more) in one single (ok, and a little tricky) update.
Hope this helps.