Question

I’m using mysqldump in a cron job to backup a database with over 2 million rows.

It creates a text file which can be used to restore the datalog from the command line.

I thought it would be useful to edit the dump before a restore as a quick way of changing values and table or column names – at least until I learn more and become confident about doing it with ALTER and UPDATE.

Editing large text files does not bother me, but I was surprised to find that in a 250 megabyte dump of my database, there were only about 300 lines. Each line was something like 800k characters long.

Is there another way of generating dumps with more control over line length?

Or should I post-process the dump with tools like sed or Perl?

Answer 1

By default, mysqldump generates only one INSERT command per table, resulting in one (very long) line of inserted data for each table that got dumped. This is essentially because the “batch” inserts are much faster than if it generated a separate INSERT query for every record in every table.

So, it’s not that mysqldump has created arbitrarily long lines, and you can just impose some other cutoff length. The lines are long for a reason.

If it’s really important to get the INSERTs broken down onto multiple lines, you can indicate that with:

mysqldump --extended-insert=FALSE --complete-insert=TRUE ...

Note, however, that restoring tables will take longer in this format.