support retaining platform instance casing

metadata-ingestion/src/datahub/sql_parsing/schema_resolver.py

@@ -90,7 +90,9 @@ def schema_count(self) -> int:
             )[0][0]
         )
 
-    def get_urn_for_table(self, table: _TableName, lower: bool = False) -> str:
+    def get_urn_for_table(
+        self, table: _TableName, lower: bool = False, mixed: bool = False
+    ) -> str:
         # TODO: Validate that this is the correct 2/3 layer hierarchy for the platform.
 
         table_name = ".".join(
@@ -101,7 +103,10 @@ def get_urn_for_table(self, table: _TableName, lower: bool = False) -> str:
 
         if lower:
             table_name = table_name.lower()
-            platform_instance = platform_instance.lower() if platform_instance else None
+            if not mixed:
+                platform_instance = (
+                    platform_instance.lower() if platform_instance else None
+                )
 
         if self.platform == "bigquery":
             # Normalize shard numbers and other BigQuery weirdness.
@@ -131,6 +136,20 @@ def resolve_table(self, table: _TableName) -> Tuple[str, Optional[SchemaInfo]]:
             if schema_info:
                 return urn_lower, schema_info
 
+        # Our treatment of platform instances when lowercasing urns
+        # is inconsistent. In some places (e.g. Snowflake), we lowercase
+        # the table names but not the platform instance. In other places
+        # (e.g. Databricks), we lowercase everything because it happens
+        # via the automatic lowercasing helper.
+        # See https://github.com/datahub-project/datahub/pull/8928.
+        # While we have this sort of inconsistency, we should also
+        # check the mixed case urn, as a last resort.
+        urn_mixed = self.get_urn_for_table(table, lower=True, mixed=True)
+        if urn_mixed not in {urn, urn_lower}:
+            schema_info = self._resolve_schema_info(urn_mixed)
+            if schema_info:
+                return urn_mixed, schema_info
+
         if self._prefers_urn_lower():
             return urn_lower, None
         else:

metadata-ingestion/tests/unit/sql_parsing/test_schemaresolver.py

@@ -41,6 +41,11 @@ def test_get_urn_for_table_lowercase():
         == "urn:li:dataset:(urn:li:dataPlatform:mssql,uppercased-instance.database.dataset.table,PROD)"
     )
 
+    assert (
+        schema_resolver.get_urn_for_table(table=table, lower=True, mixed=True)
+        == "urn:li:dataset:(urn:li:dataPlatform:mssql,Uppercased-Instance.database.dataset.table,PROD)"
+    )
+
 
 def test_get_urn_for_table_not_lower_should_keep_capital_letters():
     schema_resolver = SchemaResolver(