DerGut commented on code in PR #3000:
URL: https://github.com/apache/iceberg-rust/pull/3000#discussion_r3812961069


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crates/integrations/datafusion/src/catalog_access.rs:
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@@ -0,0 +1,192 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+use std::collections::HashMap;
+use std::sync::Arc;
+
+use async_trait::async_trait;
+use datafusion::catalog::Session;
+use datafusion::error::Result as DFResult;
+use iceberg::table::Table;
+use iceberg::{
+    Catalog, Namespace, NamespaceIdent, Result, SessionCatalog, 
SessionContext, TableCommit,
+    TableCreation, TableIdent,
+};
+
+use crate::SessionContextResolver;
+
+/// Describes how the DataFusion integration accesses an Iceberg catalog.
+///
+/// A catalog can either be accessed directly through [`Catalog`] or through a
+/// [`SessionCatalog`] bound to an Iceberg [`SessionContext`]. Operations that
+/// receive a DataFusion session resolve and bind its context once. Operations
+/// for which DataFusion provides no session reuse one anonymous fallback
+/// context so session-scoped catalog state remains stable across those calls.
+#[derive(Clone, Debug)]
+pub(crate) enum CatalogAccess {
+    /// A catalog accessed directly through the [`Catalog`] API.
+    Direct(Arc<dyn Catalog>),
+
+    /// A session-aware catalog, its resolver, and the stable context used by
+    /// DataFusion APIs that do not expose a session.
+    SessionAware {
+        catalog: Arc<dyn SessionCatalog>,
+        resolver: Arc<dyn SessionContextResolver>,
+        fallback_context: SessionContext,
+    },
+}
+
+impl CatalogAccess {
+    pub(crate) fn with_session(&self, session: &dyn Session) -> 
DFResult<Arc<dyn Catalog>> {

Review Comment:
   > in DataFusion, there should always be a Session present, so I'm not sure 
in which situation it makes sense to not pass it.
   
   Most Iceberg users do not generally deal with sessions and therefore use a 
simplified `Catalog` trait that is unaware of sessions.
   I think in the DataFusion integration we can discuss whether or not we want 
to keep the old constructor that's based on that trait. This implementation 
preserves that constructor.



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