feat: add a method for table existence check about ibis HOT 5 OPEN

So, as a workaround, I had to figure out every exception and catch specific ones depending on backend.

Welcome to Ibis! 😀

from ibis.

the best way to check table existence is by running table_name in list_tables(like=table_name)

Depending on what you intend to do if it does exist, it might be more efficient to do con.table(table_name) and branch if that operation fails. In the case it exists though, creating the table will do some work to fetch the schema and construct a ibis.Table object.

try:
    t = con.table(table_name)
except Exception:
    # table doesn't exist
    ...
else:
    # table does exist
    ...

That said, a builtin method on con just checking for existence could definitely be made more efficient.

Can you comment a little more on your use case here? In what cases are you checking for the existence of tables?

from ibis.

Thank you for your reply @jcrist

The problem with this approach is that Exception is too broad; what if some sort of connection failure happens? Table existence is not checked in this case. And there is no any specific exception for missing table error: all implementations of backend.table(...) raise their own exception types. So, as a workaround, I had to figure out every exception and catch specific ones depending on backend.

About the use case: I develop a service that manages tables, I do not work with hardcoded table names, they are supplied by users. User provides a table name and the service needs to check whether the table exists.

from ibis.

I develop a service that manages tables, I do not work with hardcoded table names, they are supplied by users. User provides a table name and the service needs to check whether the table exists.

What actions do you do if the table exists already? What do you do if it doesn't exist?

Not asking to argue against adding table_exists (or some other equivalent method with a different name), just wondering if there are other methods where we might want to add overwrite, or exists_ok kwargs to to improve this usecase.

from ibis.

What actions do you do if the table exists already? What do you do if it doesn't exist?

Mostly 2 cases:

1. create_table. In this case, it would be nice to have a syntax that runs create table if not exists. In some cases it is helpful to get as a result whether the table was created or existed before (so to make some actions on it, like migration or data cleanup).
2. some business logic, i.e. there is no immediate calls to Ibis afterwards, or it requires some mode complex custom logic before any further Ibis method is called.

from ibis.