feat: Update result_set.proto to return undeclared parameters in Exec…

…uteSql API (#841)

* feat: Update result_set.proto to return undeclared parameters in ExecuteSql API

PiperOrigin-RevId: 480025979

Source-Link: googleapis/googleapis@cb6fbe8

Source-Link: googleapis/googleapis-gen@bf166b8
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google/cloud/spanner_v1/types/result_set.py

@@ -238,6 +238,20 @@ class ResultSetMetadata(proto.Message):
             If the read or SQL query began a transaction
             as a side-effect, the information about the new
             transaction is yielded here.
+        undeclared_parameters (google.cloud.spanner_v1.types.StructType):
+            A SQL query can be parameterized. In PLAN mode, these
+            parameters can be undeclared. This indicates the field names
+            and types for those undeclared parameters in the SQL query.
+            For example, a SQL query like
+            ``"SELECT * FROM Users where UserId = @userId and UserName = @userName "``
+            could return a ``undeclared_parameters`` value like:
+
+            ::
+
+                "fields": [
+                  { "name": "UserId", "type": { "code": "INT64" } },
+                  { "name": "UserName", "type": { "code": "STRING" } },
+                ]
     """
 
     row_type = proto.Field(
@@ -250,6 +264,11 @@ class ResultSetMetadata(proto.Message):
         number=2,
         message=gs_transaction.Transaction,
     )
+    undeclared_parameters = proto.Field(
+        proto.MESSAGE,
+        number=3,
+        message=gs_type.StructType,
+    )
 
 
 class ResultSetStats(proto.Message):