Translate DROP FOREIGN TABLE and refuse it with CASCADE

src/impls/translator_impls/statement.rs

@@ -413,6 +413,7 @@ fn drop_label(object_type: ObjectType) -> &'static str {
         ObjectType::Stage => "DROP STAGE",
         ObjectType::Stream => "DROP STREAM",
         ObjectType::Warehouse => "DROP WAREHOUSE",
+        ObjectType::ForeignTable => "DROP FOREIGN TABLE",
         ObjectType::Table
         | ObjectType::View
         | ObjectType::Index
@@ -1890,11 +1891,8 @@ impl crate::traits::translator::TranslatorWithContext for Statement {
                         }
                         statements
                     }
-                    // A schema, role, or type never reached the output, so
-                    // dropping the statement removes nothing that exists. The
-                    // exceptions are the two that would destroy tables: a
-                    // cascading DROP SCHEMA removes every table in the schema,
-                    // and DROP DATABASE removes the lot.
+                    // These never reached the output, so a drop removes nothing
+                    // unless it cascades into tables or views that did.
                     ObjectType::Schema if *cascade => {
                         return Err(reject_unsupported_statement(
                             self,
@@ -1903,6 +1901,14 @@ impl crate::traits::translator::TranslatorWithContext for Statement {
                  determined. Drop the tables by name instead.",
                         ));
                     }
+                    ObjectType::ForeignTable if *cascade => {
+                        return Err(reject_unsupported_statement(
+                            self,
+                            "A cascading DROP FOREIGN TABLE also deletes the views that read the \
+                 table, and those views reach the output although the table does not. Drop \
+                 the views by name instead.",
+                        ));
+                    }
                     ObjectType::Database | ObjectType::MaterializedView => {
                         return Err(reject_unsupported_statement(
                             self,
@@ -1918,7 +1924,8 @@ impl crate::traits::translator::TranslatorWithContext for Statement {
                     | ObjectType::Collation
                     | ObjectType::Stage
                     | ObjectType::Stream
-                    | ObjectType::Warehouse => {
+                    | ObjectType::Warehouse
+                    | ObjectType::ForeignTable => {
                         drop_with_warning(
                             drop_label(*object_type),
                             REASON_DROP_OF_ABSENT_OBJECT,

tests/test_drop_statements.rs

@@ -531,6 +531,18 @@ fn drop_database_is_rejected() {
     );
 }
 
+/// A cascading `DROP FOREIGN TABLE` also deletes the views over the table,
+/// which reach the output.
+#[test]
+fn drop_foreign_table_cascade_is_rejected() {
+    let error = translate_statement("DROP FOREIGN TABLE remote_users CASCADE;")
+        .expect_err("a cascading DROP FOREIGN TABLE must be reported");
+    assert!(
+        error.to_string().contains("DROP FOREIGN TABLE remote_users CASCADE"),
+        "expected the error to name the statement, got {error}"
+    );
+}
+
 #[test]
 fn test_drop_sequence_ignored() -> Result<(), Box<dyn std::error::Error>> {
     let translated = translate_statement("DROP SEQUENCE my_sequence;")?;

tests/test_no_statement_is_silently_dropped.rs

@@ -212,6 +212,8 @@ const CASES: &[Case] = &[
     // Warned and dropped: foreign data and credentials.
     warned("CREATE SERVER srv FOREIGN DATA WRAPPER postgres_fdw"),
     warned("CREATE FOREIGN TABLE ft (id INT) SERVER srv"),
+    warned("DROP FOREIGN TABLE ft"),
+    warned("COMMENT ON FOREIGN TABLE ft IS 'note'"),
     warned("CREATE CONNECTOR c TYPE 'mysql'"),
     warned("ALTER CONNECTOR c SET URL 'u'"),
     warned("DROP CONNECTOR c"),