The fix for bug 31148 is not correct. It does not
have a relation to the problem described in this bug.
And removing the fix will not make the bug to re-appear.
Fixed the bug #31974 by removing the fix for bug 31148
and adding a test case.


mysql-test/r/key.result:
  Bug #31974: test case
mysql-test/t/key.test:
  Bug #31974: test case
sql/sql_select.cc:
  Bug #31974: revert the fix for bug 31148