How can I prevent accidentally overwriting an already existing database? - basex

Question

I'm adding BaseX to an existing web application and currently writing code to import data into it. The documentation is crystal-clear that
An existing database will be overwritten.
Finding this behavior mindboggingly dangerous, I tried it with the hope that the documentation was wrong but unfortunately my test confirmed it. For instance, using basexclient I can do this:
> create db test
Database 'test' created in 12.03 ms.
> create db test
Database 'test' created in 32.43 ms.
>
I can also replicate this behavior with the Python client, which is I what I'm actually using for my application. Reducing my code to the essentials:
session = BaseXClient.Session("127.0.0.1", 1984, "admin", "admin")
session.create("test", "")
It does not matter whether test exists or not, the whole thing is overwritten if it exists.
How can I work around this dangerous default behavior? I'd would like to prevent the possibility of missteps in production.

Answer 1

You can issue a list command before you create your database. For instance with the command line client if the database does not exist:
> list foo
Database 'foo' was not found.
Whereas if the database exists:
> list test
Input Path Type Content-Type Size
------------------------------------
This is a database that is empty so it does not show any contents but at least you do not get the error message. When you use a client you have to check whether it errors out or not. With the Python client you could do:
def exists(session, db):
try:
session.execute("list " + db)
except IOError as ex:
if ex.message == "Database '{0}' was not found.".format(db):
return False
raise
return True
The client raises IOError if the server raises an error, which is a very generic way to report a problem. So you have to test the error message to figure out what is going on. We reraise if it happens that the error message is not the one which pertains to our test. This way we don't swallow exceptions caused by unrelated issues.
With that function you could do:
session = BaseXClient.Session("127.0.0.1", 1984, "admin", "admin")
if exists(session, "test"):
raise SomeRelevantException("Oi! You are about to overwrite your database!")
session.create("test", "")