Support OR & AND within condition expression.

[fogfish]

There is a common pitfall with optimistic locking when application puts item. The item might not exists or the item might be update in other thread.

The existing code might look like

item, err := db.Get(...)
if recoverNotFound(err) {
  item = // New Item
  new = true
}

if new {
  db.Put(..., item, Field.NotExists())
} else {
  db.Put(..., item, Field.Eq(item.Some))
}

It would be helpful to have ability to compose condition checks into the single expression

db.Put(..., item,
  ddb.Or(Field.NotExists(), Field.Eq(item.Some)),
)

[Cleanfastllc]

Yes****