title: INSERT INTO WITH (TABLOCK) ocasionally not minimally logged
body: <p>I have an strange issue when loading a sql server 2016 (SP2 CU10) columnstore table. I'm using the query hint TABLOCK, so it should be minimally logged. On occasions (let's say 1 every 20 executions) the query will consume the full disk due to log growth of the transaction (100GB+). Only then to execute the exact same query with the exact same data a few minutes later, with log of basically nothing (10MB).</p>
  
  <p>The query is as follows and on average loads around 100 million rows</p>
  
  <pre><code>INSERT INTO dbo.tbl1 WITH (TABLOCK)
  SELECT cols FROM tbl2
  </code></pre>
  
  <p>Checking query store, the plan is exactly the same between the "normal" execution and the "log growth" execution.
  The only assumption I have is due to server conditions at that moment. If there is server pressure the query decides to log the full insert...but I cant find anything in relation to this.</p>
  
  <p>Any ideas?</p>