Mysql – SSD vs HDD for databases

First, each time you UPDATE the status column, you are having to update the index as well (source). Evaluate your indexing to see if you really need the index on the status column. My guess is no, since it has an extremely low cardinality and MySQL probably won't use it anyway.

If you ignore me and think you do need it, follow the advice in the article to drop the index before your loop and re-add it after you're done.

Here are some other things you might do if that doesn't help:

• You are taking all the columns from the data but only using number. Don't do a SELECT *, but instead a SELECT number. That won't help your writes, but it is a good performance practice. Only select the columns you're using.

• Your number index isn't getting used at all. This means it is not unique enough to be useful for updating. (Slight tangent: how many rows does a single UPDATE affect?) I would drop it, or at least add it to process index.

• It looks like process is unique enough for MySQL to whittle the amount of rows down to 16k, instead of 1 million. In light of this, I would add AND process=x to your update statement (I'm assuming you know process from the original SELECT statement):

  -- FAILED--
  UPDATE data SET status = 2, error='$error' WHERE process=X AND number = $data['number']
  
  -- SUCCESS --
  UPDATE data SET status = 1 WHERE process=X AND number = $data['number']
  

A hint about unnecessary indexes in InnoDB. InnoDB is using a hidden 'primary key' (since you don't have one defined) and is using that when it writes the indexes. So for each Index you're using, you add the size of the index + the size of the hidden primary key to the data file. If you're not using the index (or MySQL can't use it), you are wasting space and adding overhead each time you insert a new number (same for status, as discussed earlier)

You should store your value for FIELD1 in a TABLE, instead of in a bunch of variables. Make a three level index, a COVERED index specifically.

your IN clause is preposterous. I mean.. Learn how to Normalize.

THIS:

WHERE Field1 IN ('aaaaaaa','bbbbbbb','ccccccc',...,'nnnnnnn' )   

is actually SLOWER than this:

SELECT Field1,Date  
FROM schema.table1  
WHERE Field1 = 'aaaaaaa'   
patientid = 'abcdefg'  
AND Date <= 'xxxx-xx-xx'  
UNION
SELECT Field1,Date  
FROM schema.table1  
WHERE Field1 = 'bbbbbbb'   
patientid = 'abcdefg'  
AND Date <= 'xxxx-xx-xx'  
UNION
SELECT Field1,Date  
FROM schema.table1  
WHERE Field1 = 'ccccccc'   
patientid = 'abcdefg'  
AND Date <= 'xxxx-xx-xx'  
UNION
SELECT Field1,Date  
FROM schema.table1  
WHERE Field1 = 'nnnnnnn'   
patientid = 'abcdefg'  
AND Date <= 'xxxx-xx-xx'  
order by Field1,Date