命令不在cassandra工作

I'm a newbie in cassandra and I have an issue with "sort".

我是cassandra的新手,我有一个“排序”的问题。

My table is very simple, It like that:

我的表很简单,就像那样:

CREATE TABLE test.user_daily_report (
    stringdate bigint,
    m_date date,
    users int,
    PRIMARY KEY (stringdate, m_date)
) WITH CLUSTERING ORDER BY (m_date DESC)
   AND read_repair_chance = 0.0
   AND dclocal_read_repair_chance = 0.1
   AND gc_grace_seconds = 864000
   AND bloom_filter_fp_chance = 0.01
   AND caching = { 'keys' : 'ALL', 'rows_per_partition' : 'NONE' }
   AND comment = ''
   AND compaction = { 'class' : 'org.apache.cassandra.db.compaction.SizeTieredCompactionStrategy', 'max_threshold' : 32, 'min_threshold' : 4 }
   AND compression = { 'chunk_length_in_kb' : 64, 'class' : 'org.apache.cassandra.io.compress.LZ4Compressor' }
   AND default_time_to_live = 0
   AND speculative_retry = '99PERCENTILE'
   AND min_index_interval = 128
   AND max_index_interval = 2048
   AND crc_check_chance = 1.0;

But the result not have any effect of sort:

但结果没有任何排序的影响:

When I try to order by m_date i meet this issue:

当我尝试通过m_date订购时,我遇到了这个问题:

Please help me, It makes me confuse a lot.

请帮帮我,这让我很困惑。

Thanks

1 个解决方案

#1

In contrast to traditional relational database, in Cassandra ORDER BY works only inside partition - when you specify the WHERE condition on partition key (stringdate in your example), i.e., select * from table where stringdate = 'something' order by m_date desc - in this case data related to particular stringdate will be sorted because they are in the same partition.

与传统的关系数据库相比,在Cassandra中,ORDER BY仅在分区内部工作 - 当您在分区键上指定WHERE条件时(在您的示例中为stringdate),即,从表中选择*,其中stringdate ='something'顺序由m_date desc - in在这种情况下,与特定stringdate相关的数据将被排序,因为它们位于同一分区中。

In your case, you're receiving all results from Cassandra because you added 'ALLOW FILTERING' - in this case, Cassandra performs scanning of the whole cluster using your condition, fetches data, and returns it to you - but it didn't perform any sorting.

在您的情况下,您收到了Cassandra的所有结果,因为您添加了“允许过滤” - 在这种情况下,Cassandra使用您的条件执行整个群集的扫描,获取数据并将其返回给您 - 但它没有执行任何排序。

I recommend to watch "DS220: Data Modeling" course from DataStax Academy - they provide a lot of useful information...

我建议从DataStax Academy观看“DS220:数据建模”课程 - 它们提供了许多有用的信息......

P.S. Can you describe what task do you want to solve? I believe that you need to change data model.

附:你能描述一下你想要解决的任务吗?我相信你需要改变数据模型。

#1