feat(bigquery): support mutable clustering configuration (#3950)

* feat(bigquery): support mutable clustering configuration

internal issue 185493320

Author: shollyman

Diff for: bigquery/table.go

@@ -356,7 +356,7 @@ func (rpr *RangePartitioningRange) toBQ() *bq.RangePartitioningRange {
 	}
 }
 
-// Clustering governs the organization of data within a partitioned table.
+// Clustering governs the organization of data within a managed table.
 // For more information, see https://cloud.google.com/bigquery/docs/clustered-tables
 type Clustering struct {
 	Fields []string
@@ -681,6 +681,10 @@ func (tm *TableMetadataToUpdate) toBQ() (*bq.Table, error) {
 		t.EncryptionConfiguration = tm.EncryptionConfig.toBQ()
 	}
 
+	if tm.Clustering != nil {
+		t.Clustering = tm.Clustering.toBQ()
+	}
+
 	if !validExpiration(tm.ExpirationTime) {
 		return nil, invalidTimeError(tm.ExpirationTime)
 	}
@@ -750,6 +754,11 @@ type TableMetadataToUpdate struct {
 	// When updating a schema, you can add columns but not remove them.
 	Schema Schema
 
+	// The table's clustering configuration.
+	// For more information on how modifying clustering affects the table, see:
+	// https://cloud.google.com/bigquery/docs/creating-clustered-tables#modifying-cluster-spec
+	Clustering *Clustering
+
 	// The table's encryption configuration.
 	EncryptionConfig *EncryptionConfig
 

Diff for: bigquery/table_test.go

@@ -399,6 +399,12 @@ func TestTableMetadataToUpdateToBQ(t *testing.T) {
 				ForceSendFields:        []string{"RequirePartitionFilter"},
 			},
 		},
+		{
+			tm: TableMetadataToUpdate{Clustering: &Clustering{Fields: []string{"foo", "bar"}}},
+			want: &bq.Table{
+				Clustering: &bq.Clustering{Fields: []string{"foo", "bar"}},
+			},
+		},
 	} {
 		got, _ := test.tm.toBQ()
 		if !testutil.Equal(got, test.want) {