Hi,

I'm running tests on Postgres and it seems that dropping constraints do not include IF EXISTS before the constraint name anymore.

E.g. I see similar logs to the one below:

Thread-273] [o.h.t.s.i.SchemaDropperImpl$DelayedDropActionImpl:541] HHH000478: Unsuccessful: alter table if exists some_table drop constraint FKh7ccvqx4dfye245j4d0hll27f

Looking a bit into the code I noticed some problems:

• Apparently ForeignKey.sqlDropString() (or in fact any other sqlDropString() method) seems to be never called
• Dialect.supportsIfExistsBeforeConstraintName() doesn't seem to be consistently applied. Constraint actually doesn't check it, ForeignKey does - but yet again: I can't see the call site of any sqlDropString(). StandardForeignKeyExporter.getSqlDropStrings() which is called in the process of dropping the schema doesn't respect those settings as well.

Any help and clarification is appreciated.

Cheers,
Christoph