Context:
When introducing the optimize rest API tests and manually testing them against MySQL we found out that there's an issue. A support case SUPPORT-7162 opened by Nokia shows that they're already affected by it. 

A similar issue was already fixed with CAM-10513.

Steps to reproduce:

• given:
  • I have MySQL as a database connected to the engine
  • I have several decision instances evaluated
  • In total, I have more than 2100 decision variables created in the engine
• when:
  • I use the Optimize rest API or the engine history decision instance endpoint to fetch all the decision instances with their decision variables at once
• then:
  • I get the following error in the engine (see the full log attached full_error.txt)
• expected:
  • I can fetch all the data without any problems

AT:

• the bug is fixed