test: match kernel table-type filters by exact case

Align Kernel E2E with case-sensitive filtering from databricks-sql-kernel#393. Check uppercase matches and lowercase/mixed-case empty results, and update stale filter comments.

Signed-off-by: Cathleen Yan <58714163+cathleeny@users.noreply.github.com>

Author: cathleeny

src/databricks/sql/backend/kernel/client.py

@@ -1045,11 +1045,9 @@ def get_tables(
         if self._kernel_session is None:
             raise InterfaceError("get_tables requires an open session.")
         try:
-            # ``table_types`` is filtered kernel-side (the kernel applies
-            # it to the reshaped result, case-insensitively as of the
-            # batch-3 kernel change), so we forward it and let the kernel
-            # do the work — no connector-side drain + refilter. Passing it
-            # through preserves streaming for large schemas.
+            # The kernel filters ``table_types`` with case-sensitive
+            # matching for Thrift parity. Forward the values unchanged
+            # to preserve those semantics and streaming for large schemas.
             stream = self._kernel_session.metadata().list_tables(
                 catalog=escape_metadata_catalog_name(
                     _catalog_or_none(catalog_name), self._escape_catalog_name

tests/e2e/test_kernel_backend.py

@@ -383,12 +383,12 @@ def test_columns_with_empty_string_filter_matches_nothing(conn, empty_filter):
         assert cur.fetchall() == []
 
 
-def test_tables_table_types_filter_is_case_insensitive(conn):
-    """Lowercase ``table_types=['view']`` / uppercase ``['TABLE']``
-    each match the right object regardless of case — locks the
-    kernel-side case-insensitive ``table_types`` match (batch-3 kernel
-    B2) end-to-end plus the connector drain removal (the filter now
-    runs kernel-side, not client-side).
+def test_tables_table_types_filter_is_case_sensitive(conn):
+    """Table types match exact case, consistent with Thrift.
+
+    Uppercase ``['VIEW']`` / ``['TABLE']`` match the corresponding
+    object; lowercase and mixed-case values match no objects. The
+    kernel applies the filter to values forwarded by the connector.
 
     Self-contained: creates a table + a view over it in the session's
     default (writable) schema, scopes the lookup to a unique name
@@ -411,12 +411,12 @@ def _names_and_types():
                 ni, ti = cols.index("TABLE_NAME"), cols.index("TABLE_TYPE")
                 return {(r[ni], r[ti]) for r in rows}
 
-            # Lowercase 'view' must match the VIEW (and only it).
+            # Uppercase 'VIEW' must match the VIEW (and only it).
             cur.tables(
                 catalog_name=cat,
                 schema_name=sch,
                 table_name=name_pat,
-                table_types=["view"],
+                table_types=["VIEW"],
             )
             assert _names_and_types() == {(vw, "VIEW")}
 
@@ -428,6 +428,16 @@ def _names_and_types():
                 table_types=["TABLE"],
             )
             assert _names_and_types() == {(tbl, "TABLE")}
+
+            # Lowercase and mixed-case requests must not match either type.
+            for table_type in ("view", "View", "table", "Table"):
+                cur.tables(
+                    catalog_name=cat,
+                    schema_name=sch,
+                    table_name=name_pat,
+                    table_types=[table_type],
+                )
+                assert _names_and_types() == set(), table_type
         finally:
             cur.execute(f"DROP VIEW IF EXISTS {vw}")
             cur.execute(f"DROP TABLE IF EXISTS {tbl}")

tests/unit/test_kernel_client.py

@@ -1626,7 +1626,7 @@ def _make_tables_stream() -> MagicMock:
 
 def test_get_tables_forwards_table_types_to_kernel():
     """``table_types`` is forwarded verbatim to the kernel's
-    ``list_tables`` (which filters case-insensitively) — the
+    ``list_tables`` (which filters case-sensitively) — the
     connector no longer drains + refilters client-side. The stream
     flows back through the normal ``KernelResultSet`` path unchanged."""
     c = _make_client()