feat(spanner): Add support for Cloud Spanner Incremental Backups

protos/google/spanner/admin/database/v1/backup.proto

@@ -103,6 +103,24 @@ message Backup {
   // Output only. Size of the backup in bytes.
   int64 size_bytes = 5 [(google.api.field_behavior) = OUTPUT_ONLY];
 
+  // Output only. The number of bytes that will be freed by deleting this
+  // backup. This value will be zero if, for example, this backup is part of an
+  // incremental backup chain and younger backups in the chain require that we
+  // keep its data. For backups not in an incremental backup chain, this is
+  // always the size of the backup. This value may change if backups on the same
+  // chain get created, deleted or expired.
+  int64 freeable_size_bytes = 15 [(google.api.field_behavior) = OUTPUT_ONLY];
+
+  // Output only. For a backup in an incremental backup chain, this is the
+  // storage space needed to keep the data that has changed since the previous
+  // backup. For all other backups, this is always the size of the backup. This
+  // value may change if backups on the same chain get deleted or expired.
+  //
+  // This field can be used to calculate the total storage space used by a set
+  // of backups. For example, the total space used by all backups of a database
+  // can be computed by summing up this field.
+  int64 exclusive_size_bytes = 16 [(google.api.field_behavior) = OUTPUT_ONLY];
+
   // Output only. The current state of the backup.
   State state = 6 [(google.api.field_behavior) = OUTPUT_ONLY];
 
@@ -168,6 +186,23 @@ message Backup {
   // single backup schedule URI associated with creating this backup.
   repeated string backup_schedules = 14
       [(google.api.field_behavior) = OUTPUT_ONLY];
+
+  // Output only. Populated only for backups in an incremental backup chain.
+  // Backups share the same chain id if and only if they belong to the same
+  // incremental backup chain. Use this field to determine which backups are
+  // part of the same incremental backup chain. The ordering of backups in the
+  // chain can be determined by ordering the backup `version_time`.
+  string incremental_backup_chain_id = 17
+      [(google.api.field_behavior) = OUTPUT_ONLY];
+
+  // Output only. Data deleted at a time older than this is guaranteed not to be
+  // retained in order to support this backup. For a backup in an incremental
+  // backup chain, this is the version time of the oldest backup that exists or
+  // ever existed in the chain. For all other backups, this is the version time
+  // of the backup. This field can be used to understand what data is being
+  // retained by the backup system.
+  google.protobuf.Timestamp oldest_version_time = 18
+      [(google.api.field_behavior) = OUTPUT_ONLY];
 }
 
 // The request for
@@ -705,3 +740,11 @@ message CopyBackupEncryptionConfig {
 // A full backup stores the entire contents of the database at a given
 // version time.
 message FullBackupSpec {}
+
+// The specification for incremental backup chains.
+// An incremental backup stores the delta of changes between a previous
+// backup and the database contents at a given version time. An
+// incremental backup chain consists of a full backup and zero or more
+// successive incremental backups. The first backup created for an
+// incremental backup chain is always a full backup.
+message IncrementalBackupSpec {}

protos/google/spanner/admin/database/v1/backup_schedule.proto

@@ -83,6 +83,9 @@ message BackupSchedule {
   oneof backup_type_spec {
     // The schedule creates only full backups.
     FullBackupSpec full_backup_spec = 7;
+
+    // The schedule creates incremental backup chains.
+    IncrementalBackupSpec incremental_backup_spec = 8;
   }
 
   // Output only. The timestamp at which the schedule was last updated.