title: Mysql (MariaDB) How to figure out why PROCESSLIST MEMORY_USAGE continuously growing unexpectedly
body: <p>I have a database with a few tables in it.  One of the tables has ~3000 rows each with ~20 columns.  Every 30 seconds one of the rows in the table is UPDATE'ed with new information.  I'm having a problem where sometimes (infrequently) I will notice the memory being used by the process that is updating the rows will start increasing "indefinitely" (I stop the process before it stops growing, but I'm sure it stops at some upper limit).  The database is not growing during this time.  Only existing rows are being updated.</p>
  
  <p>I'm looking for ideas on what could cause the memory usage to start going up so that I can prevent it from happening.  Since most of the time the memory usage stays the same despite running the same update process I'm not sure what condition is triggering the failure state (growing memory usage) so that I can recreate the failure on demand.</p>
  
  <p>The table is using the Memory engine and I've seen the same failure using the InnoDB engine.</p>
  
  <p>The MEMORY_USAGE I'm looking at is in the table returned by the below query.  Are there other mysql variables I can look at to get a better idea of what specifically is using up the memory?  </p>
  
  <pre><code>SELECT * FROM INFORMATION_SCHEMA.PROCESSLIST
  </code></pre>