fix(backends): make current_database implementation and API consist…

…ent across all backends

ibis/backends/base/__init__.py

@@ -734,7 +734,8 @@ def current_database(self) -> str | None:
         Returns
         -------
         str | None
-            Name of the current database.
+            Name of the current database or `None` if the backend supports the
+            concept of a database but doesn't support multiple databases.
         """
 
     @staticmethod

ibis/backends/base/sql/alchemy/__init__.py

@@ -452,7 +452,7 @@ def schema(self, name: str) -> sch.Schema:
         return self.database().schema(name)
 
     @property
-    def current_database(self) -> str:
+    def current_database(self) -> str | None:
         """The name of the current database this client is connected to."""
         return self.database_name
 

ibis/backends/bigquery/__init__.py

@@ -326,7 +326,7 @@ def raw_sql(self, query: str, results=False, params=None):
         return self._execute(query, results=results, query_parameters=query_parameters)
 
     @property
-    def current_database(self) -> str:
+    def current_database(self) -> str | None:
         return self.dataset
 
     def database(self, name=None):

ibis/backends/clickhouse/__init__.py

@@ -192,8 +192,10 @@ def version(self) -> str:
         return self.con.server_version
 
     @property
-    def current_database(self) -> str:
-        return self.con.database
+    def current_database(self) -> str | None:
+        with closing(self.raw_sql("SELECT currentDatabase()")) as result:
+            [(db,)] = result.result_rows
+        return db
 
     def list_databases(self, like: str | None = None) -> list[str]:
         with closing(self.raw_sql("SELECT name FROM system.databases")) as result:

ibis/backends/datafusion/__init__.py

@@ -73,7 +73,7 @@ def do_connect(
             self.register(path, table_name=name)
 
     @property
-    def current_database(self) -> str:
+    def current_database(self) -> str | None:
         raise NotImplementedError()
 
     def list_databases(self, like: str | None = None) -> list[str]:

ibis/backends/duckdb/__init__.py

@@ -78,7 +78,7 @@ class Backend(BaseAlchemyBackend, CanCreateSchema):
     supports_create_or_replace = True
 
     @property
-    def current_database(self) -> str:
+    def current_database(self) -> str | None:
         query = sa.select(sa.func.current_database())
         with self.begin() as con:
             return con.execute(query).scalar()

ibis/backends/impala/__init__.py

@@ -414,7 +414,7 @@ def _get_list(self, cur):
         return list(map(operator.itemgetter(0), tuples))
 
     @property
-    def current_database(self):
+    def current_database(self) -> str | None:
         # XXX The parent `Client` has a generic method that calls this same
         # method in the backend. But for whatever reason calling this code from
         # that method doesn't seem to work. Maybe `con` is a copy?

ibis/backends/pandas/__init__.py

@@ -82,7 +82,7 @@ def version(self) -> str:
         return pd.__version__
 
     @property
-    def current_database(self):
+    def current_database(self) -> str | None:
         raise NotImplementedError('pandas backend does not support databases')
 
     def list_tables(self, like=None, database=None):

ibis/backends/polars/__init__.py

@@ -50,7 +50,8 @@ def do_connect(
     def version(self) -> str:
         return pl.__version__
 
-    def current_database(self):
+    @property
+    def current_database(self) -> str | None:
         raise NotImplementedError('polars backend does not support databases')
 
     def list_tables(self, like=None, database=None):

ibis/backends/pyspark/__init__.py

@@ -169,7 +169,7 @@ def version(self):
         return pyspark.__version__
 
     @property
-    def current_database(self):
+    def current_database(self) -> str | None:
         return self._catalog.currentDatabase()
 
     def list_databases(self, like=None):

ibis/backends/trino/__init__.py

@@ -35,14 +35,17 @@ class Backend(BaseAlchemyBackend, AlchemyCanCreateSchema):
     supports_create_or_replace = False
     supports_temporary_tables = False
 
-    def current_database(self) -> str:
-        raise NotImplementedError(type(self))
-
     @cached_property
     def version(self) -> str:
         with self.begin() as con:
             return con.execute(sa.select(sa.func.version())).scalar()
 
+    @property
+    def current_database(self) -> str | None:
+        query = sa.select(sa.literal_column("current_catalog"))
+        with self.begin() as con:
+            return con.execute(query).scalar()
+
     def do_connect(
         self,
         user: str = "user",