Error: unexpected end of JSON input when restore

[D3Hunter]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

1. use nightly BR to full backup nightly tidb
   • or use 6.1.0 BR to backup 6.1.0 tidb, restore will fail with same error
2. use 6.0.0 BR to full restore 6.0.0 tidb

log
backup.log
restore.log

2. What did you expect to see? (Required)

success

3. What did you see instead (Required)

[2022/07/20 19:20:59.556 +08:00] [INFO] [collector.go:67] ["Full Restore failed summary"] [total-ranges=0] [ranges-succeed=0] [ranges-failed=0]
Error: unexpected end of JSON input

4. What is your TiDB version? (Required)

[fubinzh]

Per Dev, below scenarios are impacted:
Use br nightly to backup nightly cluster, then use br 6.0 to restore to 6.0 cluster.
Use br 6.1 to backup nightly cluster, then use br 6.0 to restore to 6.0 cluster.
Use br nightly to backup nightly cluster, then use br 5.4 to restore to 5.4 cluster.

Below scenarios are not impacted:
Use br nightly to backup nightly cluster, then use br nightly to restore to nightly cluster.

[D3Hunter]

it's caused by empty database in backup data. can workaround by using explicit filter