Summary

This PR fixes #4133.

There's problem that cached queries are remaining after DDL execution. It causes confusion that already modified or removed objects are remaining.
It can be fixed by clear cache after DDL query exection.

Changes

• Clear query caches after DDL execution.
  I think, There were 2 ways to implement this logic.

  1. Modify DefineCommand.java that is parent of DDL commands.
     I don't think it's a good idea because there are 2 problems. First, too many modification needed. And, complex structure neede to change modificationMetaId.
     

     h2database/h2/src/main/org/h2/engine/Database.java

     Line 167 in 2df8bdc

     private final AtomicLong modificationMetaId = new AtomicLong();

  2. Modify Database.java.
     It solves both of the above problems.

• Add integration tests.
  Database.java is hard to implement unit test. So, I add integration tests that can be asserted.