fix(redshift): normalize table names to lowercase for CSV uploads (#37019)

tests/unit_tests/db_engine_specs/test_redshift.py

@@ -20,6 +20,7 @@ from typing import Optional
 
 import pytest
 
+from superset.db_engine_specs.redshift import RedshiftEngineSpec
 from tests.unit_tests.db_engine_specs.utils import assert_convert_dttm
 from tests.unit_tests.fixtures.common import dttm  # noqa: F401
 
@@ -49,3 +50,32 @@ def test_convert_dttm(
     )
 
     assert_convert_dttm(spec, target_type, expected_result, dttm)
+
+
+@pytest.mark.parametrize(
+    "table_name,schema_name,expected_table,expected_schema",
+    [
+        ("BPO_mytest_2", "MySchema", "bpo_mytest_2", "myschema"),
+        ("MY_TABLE", None, "my_table", None),
+        ("already_lower", "lower_schema", "already_lower", "lower_schema"),
+    ],
+)
+def test_normalize_table_name_for_upload(
+    table_name: str,
+    schema_name: Optional[str],
+    expected_table: str,
+    expected_schema: Optional[str],
+) -> None:
+    """
+    Test that table and schema names are normalized to lowercase for Redshift.
+
+    Redshift folds unquoted identifiers to lowercase, so we need to normalize
+    table names to ensure consistent behavior when checking table existence
+    and performing replace operations.
+    """
+    normalized_table, normalized_schema = (
+        RedshiftEngineSpec.normalize_table_name_for_upload(table_name, schema_name)
+    )
+
+    assert normalized_table == expected_table
+    assert normalized_schema == expected_schema