Question

我担心“压缩分区最大字节数”的值，因为它只有89MB很高。

这是否表明模型损坏或其他问题？应用程序端没有发现问题。

使用 week_first_day，device_id 分区键，将存储在表中的数据打包到每个设备的每周存储区中。

表的数据模型：

CREATE TABLE device_data (
week_first_day timestamp,
device_id uuid,
nano_since_epoch bigint,
sensor_id uuid,
source text,
unit text,
username text,
value double,
PRIMARY KEY ((week_first_day, device_id), nano_since_epoch, sensor_id)
)

nodetool cfstats

Table: device_data
            SSTable count: 5
            Space used (live): 447558297
            Space used (total): 447558297
            Space used by snapshots (total): 0
            Off heap memory used (total): 211264
            SSTable Compression Ratio: 0.2610509614736755
            Number of partitions (estimate): 939
            Memtable cell count: 458
            Memtable data size: 63785
            Memtable off heap memory used: 0
            Memtable switch count: 0
            Local read count: 0
            Local read latency: NaN ms
            Local write count: 458
            Local write latency: 0.058 ms
            Pending flushes: 0
            Percent repaired: 99.83
            Bloom filter false positives: 0
            Bloom filter false ratio: 0.00000
            Bloom filter space used: 2216
            Bloom filter off heap memory used: 2176
            Index summary off heap memory used: 672
            Compression metadata off heap memory used: 208416
            Compacted partition minimum bytes: 43
            Compacted partition maximum bytes: 89970660
            Compacted partition mean bytes: 1100241
            Average live cells per slice (last five minutes): NaN
            Maximum live cells per slice (last five minutes): 0
            Average tombstones per slice (last five minutes): NaN
            Maximum tombstones per slice (last five minutes): 0
            Dropped Mutations: 0

Answer 1

这实际上取决于该分区中数据的访问模式-如果您经常读取整个分区，则可能会引起问题，但是如果您仅读取其中的一部分，则不应一个问题。例如，您可以通过将日期用作时段来分解分区。

请看2年前Cassandra Summit上的演讲Myths of Big Partitions-它详细介绍了如何在Cassandra 3.x中处理该问题。

nodetool cfstats压缩分区最大字节

1 个答案: