如何恢复在 Cassandra 中使用 truncate 删除的数据
How to recover data deleted using truncate in Cassandra
我在 Cassandra 中不小心截断了一个 table。我想知道是否有任何工具可以恢复其中的数据。任何帮助，将不胜感激。谢谢。
auto_snapshot (Default: true)
Whether Cassandra takes a snapshot of
the data before truncating a keyspace or dropping a table. To prevent
data loss, DataStax strongly advises using the default setting. If you
set auto_snapshot to false, data loss occurs on truncation or drop.
（取自https://docs.datastax.com/en/cassandra/3.0/cassandra/configuration/configCassandra_yaml.html）
如果幸运的话，查看旧 sstables 的快照目录。为了恢复它们“只”需要被复制回它们的原始位置。
事情是这样的：
./data1/demokeyspace/demo-0d1a38b05fe211e8875d13cbb58d64f2
./data1/demokeyspace/demo-0d1a38b05fe211e8875d13cbb58d64f2/backups
./data1/demokeyspace/demo-0d1a38b05fe211e8875d13cbb58d64f2/mc-1-big-Data.db
./data1/demokeyspace/demo-0d1a38b05fe211e8875d13cbb58d64f2/mc-1-big-Index.db
./data1/demokeyspace/demo-0d1a38b05fe211e8875d13cbb58d64f2/mc-1-big-Filter.db
./data1/demokeyspace/demo-0d1a38b05fe211e8875d13cbb58d64f2/mc-1-big-Summary.db
./data1/demokeyspace/demo-0d1a38b05fe211e8875d13cbb58d64f2/mc-1-big-Digest.crc32
./data1/demokeyspace/demo-0d1a38b05fe211e8875d13cbb58d64f2/mc-1-big-CompressionInfo.db
./data1/demokeyspace/demo-0d1a38b05fe211e8875d13cbb58d64f2/mc-1-big-Statistics.db
./data1/demokeyspace/demo-0d1a38b05fe211e8875d13cbb58d64f2/mc-1-big-TOC.txt
然后我发布了TRUNCATE demokeyspace.demo - 之后是这样的：
./data1/demokeyspace/demo-0d1a38b05fe211e8875d13cbb58d64f2
./data1/demokeyspace/demo-0d1a38b05fe211e8875d13cbb58d64f2/backups
./data1/demokeyspace/demo-0d1a38b05fe211e8875d13cbb58d64f2/snapshots
./data1/demokeyspace/demo-0d1a38b05fe211e8875d13cbb58d64f2/snapshots/truncated-1527228644868-demo
./data1/demokeyspace/demo-0d1a38b05fe211e8875d13cbb58d64f2/snapshots/truncated-1527228644868-demo/mc-1-big-Summary.db
./data1/demokeyspace/demo-0d1a38b05fe211e8875d13cbb58d64f2/snapshots/truncated-1527228644868-demo/mc-1-big-TOC.txt
./data1/demokeyspace/demo-0d1a38b05fe211e8875d13cbb58d64f2/snapshots/truncated-1527228644868-demo/mc-1-big-Digest.crc32
./data1/demokeyspace/demo-0d1a38b05fe211e8875d13cbb58d64f2/snapshots/truncated-1527228644868-demo/mc-1-big-Filter.db
./data1/demokeyspace/demo-0d1a38b05fe211e8875d13cbb58d64f2/snapshots/truncated-1527228644868-demo/mc-1-big-CompressionInfo.db
./data1/demokeyspace/demo-0d1a38b05fe211e8875d13cbb58d64f2/snapshots/truncated-1527228644868-demo/mc-1-big-Index.db
./data1/demokeyspace/demo-0d1a38b05fe211e8875d13cbb58d64f2/snapshots/truncated-1527228644868-demo/mc-1-big-Data.db
./data1/demokeyspace/demo-0d1a38b05fe211e8875d13cbb58d64f2/snapshots/truncated-1527228644868-demo/mc-1-big-Statistics.db
只需将这些文件复制回来即可。但请记住，您需要在所有节点上执行此操作，然后 运行 nodetool refresh demokeyspace demo 重新读取表（当然使用您的键空间和列族）。
我在 Cassandra 中不小心截断了一个 table。我想知道是否有任何工具可以恢复其中的数据。任何帮助，将不胜感激。谢谢。
auto_snapshot (Default: true)
Whether Cassandra takes a snapshot of the data before truncating a keyspace or dropping a table. To prevent data loss, DataStax strongly advises using the default setting. If you set auto_snapshot to false, data loss occurs on truncation or drop.
（取自https://docs.datastax.com/en/cassandra/3.0/cassandra/configuration/configCassandra_yaml.html）
如果幸运的话，查看旧 sstables 的快照目录。为了恢复它们“只”需要被复制回它们的原始位置。
事情是这样的：
./data1/demokeyspace/demo-0d1a38b05fe211e8875d13cbb58d64f2
./data1/demokeyspace/demo-0d1a38b05fe211e8875d13cbb58d64f2/backups
./data1/demokeyspace/demo-0d1a38b05fe211e8875d13cbb58d64f2/mc-1-big-Data.db
./data1/demokeyspace/demo-0d1a38b05fe211e8875d13cbb58d64f2/mc-1-big-Index.db
./data1/demokeyspace/demo-0d1a38b05fe211e8875d13cbb58d64f2/mc-1-big-Filter.db
./data1/demokeyspace/demo-0d1a38b05fe211e8875d13cbb58d64f2/mc-1-big-Summary.db
./data1/demokeyspace/demo-0d1a38b05fe211e8875d13cbb58d64f2/mc-1-big-Digest.crc32
./data1/demokeyspace/demo-0d1a38b05fe211e8875d13cbb58d64f2/mc-1-big-CompressionInfo.db
./data1/demokeyspace/demo-0d1a38b05fe211e8875d13cbb58d64f2/mc-1-big-Statistics.db
./data1/demokeyspace/demo-0d1a38b05fe211e8875d13cbb58d64f2/mc-1-big-TOC.txt
然后我发布了TRUNCATE demokeyspace.demo - 之后是这样的：
./data1/demokeyspace/demo-0d1a38b05fe211e8875d13cbb58d64f2
./data1/demokeyspace/demo-0d1a38b05fe211e8875d13cbb58d64f2/backups
./data1/demokeyspace/demo-0d1a38b05fe211e8875d13cbb58d64f2/snapshots
./data1/demokeyspace/demo-0d1a38b05fe211e8875d13cbb58d64f2/snapshots/truncated-1527228644868-demo
./data1/demokeyspace/demo-0d1a38b05fe211e8875d13cbb58d64f2/snapshots/truncated-1527228644868-demo/mc-1-big-Summary.db
./data1/demokeyspace/demo-0d1a38b05fe211e8875d13cbb58d64f2/snapshots/truncated-1527228644868-demo/mc-1-big-TOC.txt
./data1/demokeyspace/demo-0d1a38b05fe211e8875d13cbb58d64f2/snapshots/truncated-1527228644868-demo/mc-1-big-Digest.crc32
./data1/demokeyspace/demo-0d1a38b05fe211e8875d13cbb58d64f2/snapshots/truncated-1527228644868-demo/mc-1-big-Filter.db
./data1/demokeyspace/demo-0d1a38b05fe211e8875d13cbb58d64f2/snapshots/truncated-1527228644868-demo/mc-1-big-CompressionInfo.db
./data1/demokeyspace/demo-0d1a38b05fe211e8875d13cbb58d64f2/snapshots/truncated-1527228644868-demo/mc-1-big-Index.db
./data1/demokeyspace/demo-0d1a38b05fe211e8875d13cbb58d64f2/snapshots/truncated-1527228644868-demo/mc-1-big-Data.db
./data1/demokeyspace/demo-0d1a38b05fe211e8875d13cbb58d64f2/snapshots/truncated-1527228644868-demo/mc-1-big-Statistics.db
只需将这些文件复制回来即可。但请记住，您需要在所有节点上执行此操作，然后 运行 nodetool refresh demokeyspace demo 重新读取表（当然使用您的键空间和列族）。