feat: add missing_value_interpretations to AppendRowsRequest

PiperOrigin-RevId: 488693558

google/cloud/bigquery/storage/v1/storage.proto

@@ -417,6 +417,23 @@ message AppendRowsRequest {
     ProtoRows rows = 2;
   }
 
+  // An enum to indicate how to interpret missing values. Missing values are
+  // fields present in user schema but missing in rows. A missing value can
+  // represent a NULL or a column default value defined in BigQuery table
+  // schema.
+  enum MissingValueInterpretation {
+    // Invalid missing value interpretation. Requests with this value will be
+    // rejected.
+    MISSING_VALUE_INTERPRETATION_UNSPECIFIED = 0;
+
+    // Missing value is interpreted as NULL.
+    NULL_VALUE = 1;
+
+    // Missing value is interpreted as column default value if declared in the
+    // table schema, NULL otherwise.
+    DEFAULT_VALUE = 2;
+  }
+
   // Required. The write_stream identifies the target of the append operation, and only
   // needs to be specified as part of the first request on the gRPC connection.
   // If provided for subsequent requests, it must match the value of the first
@@ -454,6 +471,26 @@ message AppendRowsRequest {
   // Id set by client to annotate its identity. Only initial request setting is
   // respected.
   string trace_id = 6;
+
+  // A map to indicate how to interpret missing value for some fields. Missing
+  // values are fields present in user schema but missing in rows. The key is
+  // the field name. The value is the interpretation of missing values for the
+  // field.
+  //
+  // For example, a map {'foo': NULL_VALUE, 'bar': DEFAULT_VALUE} means all
+  // missing values in field foo are interpreted as NULL, all missing values in
+  // field bar are interpreted as the default value of field bar in table
+  // schema.
+  //
+  // If a field is not in this map and has missing values, the missing values
+  // in this field are interpreted as NULL.
+  //
+  // This field only applies to the current request, it won't affect other
+  // requests on the connection.
+  //
+  // Currently, field name can only be top-level column name, can't be a struct
+  // field path like 'foo.bar'.
+  map<string, MissingValueInterpretation> missing_value_interpretations = 7;
 }
 
 // Response message for `AppendRows`.