= Cassandra =

== CQL ==

* 列出所有的 Keyspace
{{{
cqlsh> DESCRIBE keyspaces;
}}}

* 備份 `A.A.A.A` 整個 Cassandra 的 Schema
{{{
root@cqlsh:~# cqlsh -e "DESC SCHEMA" A.A.A.A > /tmp/db_schema.cql 
}}}
* 還原整個 Cassandra 的 Schema 到另一台 `B.B.B.B` 新的機器
{{{
root@cqlsh:~# cqlsh B.B.B.B
cqlsh> source '/tmp/db_schema.cql'
}}}
* 查詢 Replication Factor
{{{
cqlsh> SELECT keyspace_name,strategy_options FROM system.schema_keyspaces;
 
 keyspace_name | strategy_options
---------------+----------------------------
 system_traces | {"replication_factor":"2"}
}}}

== nodetool ==

* 查詢叢集節點狀態
{{{
~$ nodetool status
}}}
* 強制移除故障節點
{{{
~$ nodetool removenode <HOST_ID>
}}}