Views: snapshot to skip ephermeral tables (#3720)

# Description of Changes.
fixes #3715 

The patch makes snapshots to skip ephemeral tables.

# API and ABI breaking changes
NA

# Expected complexity level and risk
1

# Testing

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reviewers to do,
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---------

Co-authored-by: joshua-spacetime <josh@clockworklabs.io>

Author: Shubham8287

crates/core/src/db/relational_db.rs

@@ -2591,7 +2591,40 @@ mod tests {
     }
 
     #[test]
-    fn test_view_tables_are_ephemeral() -> ResultTest<()> {
+    fn test_view_tables_are_ephemeral_in_commitlog() -> ResultTest<()> {
+        let stdb = TestDB::durable_without_snapshot_repo()?;
+
+        let (view_id, table_id, _, _) = setup_view(&stdb)?;
+
+        // Write some rows (reusing the same helper)
+        insert_view_row(&stdb, view_id, table_id, Identity::ONE, 10)?;
+        insert_view_row(&stdb, view_id, table_id, Identity::ZERO, 20)?;
+
+        assert!(
+            !project_views(&stdb, table_id, Identity::ZERO).is_empty(),
+            "View table should NOT be empty after insert"
+        );
+
+        // Reopen the database — view tables must not persist
+        let stdb = stdb.reopen()?;
+
+        // Validate that the view's backing table has been removed
+        assert!(
+            project_views(&stdb, table_id, Identity::ZERO).is_empty(),
+            "View table should be empty after reopening the database"
+        );
+
+        let tx = begin_mut_tx(&stdb);
+        let subs_rows = tx.lookup_st_view_subs(view_id)?;
+        assert!(
+            subs_rows.is_empty(),
+            "st_view_subs should be empty after reopening the database"
+        );
+        Ok(())
+    }
+
+    #[test]
+    fn test_view_tables_are_ephemeral_with_snapshot() -> ResultTest<()> {
         let stdb = TestDB::durable()?;
 
         let (view_id, table_id, _, _) = setup_view(&stdb)?;
@@ -2605,6 +2638,10 @@ mod tests {
             "View table should NOT be empty after insert"
         );
 
+        let root = stdb.path().snapshots();
+        let (_, repo) = make_snapshot(root.clone(), Identity::ZERO, 0, CompressType::None, false);
+        stdb.take_snapshot(&repo)?.expect("snapshot should succeed");
+
         // Reopen the database — view tables must not persist
         let stdb = stdb.reopen()?;
 

crates/datastore/src/locking_tx_datastore/committed_state.rs

@@ -1017,6 +1017,17 @@ impl CommittedState {
         (table, blob_store, pool)
     }
 
+    /// Returns an iterator over all persistent tables (i.e., non-ephemeral tables)
+    pub(super) fn persistent_tables_and_blob_store(&mut self) -> (impl Iterator<Item = &mut Table>, &HashMapBlobStore) {
+        (
+            self.tables
+                .iter_mut()
+                .filter(|(table_id, _)| !self.ephemeral_tables.contains(*table_id))
+                .map(|(_, table)| table),
+            &self.blob_store,
+        )
+    }
+
     pub fn report_data_size(&self, database_identity: Identity) {
         use crate::db_metrics::data_size::DATA_SIZE_METRICS;
 

crates/datastore/src/locking_tx_datastore/datastore.rs

@@ -282,12 +282,8 @@ impl Locking {
             tx_offset,
         );
 
-        let CommittedState {
-            ref mut tables,
-            ref blob_store,
-            ..
-        } = *committed_state;
-        let snapshot_dir = repo.create_snapshot(tables.values_mut(), blob_store, tx_offset)?;
+        let (tables, blob_store) = committed_state.persistent_tables_and_blob_store();
+        let snapshot_dir = repo.create_snapshot(tables, blob_store, tx_offset)?;
 
         Ok(Some((tx_offset, snapshot_dir)))
     }