[improve](backup) Only compress the running backup/restore job (apach…

…e#43177)

For a completed job, there's no need to save it with compressed
serialization as it has no snapshot or backup meta info, making it small
in size.

This helps maintain compatibility more easily.

fe/fe-core/src/main/java/org/apache/doris/backup/AbstractJob.java

@@ -210,8 +210,11 @@ public void write(DataOutput out) throws IOException {
             count++;
         }
 
-        if ((type == JobType.BACKUP && Config.backup_job_compressed_serialization)
-                || (type == JobType.RESTORE && Config.restore_job_compressed_serialization)) {
+        // For a completed job, there's no need to save it with compressed serialization as it has
+        // no snapshot or backup meta info, making it small in size. This helps maintain compatibility
+        // more easily.
+        if (!isDone() && ((type == JobType.BACKUP && Config.backup_job_compressed_serialization)
+                || (type == JobType.RESTORE && Config.restore_job_compressed_serialization))) {
             Text.writeString(out, COMPRESSED_JOB_ID);
             GsonUtils.toJsonCompressed(out, this);
         } else {