Question

我是cassandra的新手，目前正在试用datastax的温度示例。在示例中，我创建了一个包含以下DDL的表：

CREATE TABLE mykeyspace.temperature (
    weatherstation_id text,
    event_time timestamp,
    temperature text,
    PRIMARY KEY (weatherstation_id, event_time)
) WITH 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;

包含以下数据：

cqlsh> use mykeyspace;
cqlsh:mykeyspace> select * from temperature where weatherstation_id='1234ABCD'
              ... ;

 weatherstation_id | event_time               | temperature
-------------------+--------------------------+-------------
          1234ABCD | 2013-04-03 06:01:00+0000 |         72F
          1234ABCD | 2013-04-03 06:02:00+0000 |         73F
          1234ABCD | 2013-04-03 06:03:00+0000 |         73F
          1234ABCD | 2013-04-03 06:04:00+0000 |         74F
          1234ABCD | 2013-04-03 06:05:00+0000 |         72F
          1234ABCD | 2013-04-03 07:01:00+0000 |         72F

但是，当我运行以下cql时，过滤不起作用并仍然返回完整集：

select * from temperature where weatherstation_id='1234ABCD' and event_time > '2013-04-03 06:05:00';

我是否理解错误的情况？

Answer 1

不，你正确了解情况。但是在使用时间戳时，Cassandra假设您正在使用当地的GMT偏移量。当我运行您的上一个查询时，我根本不会返回任何行。但是当我指定GMT偏移量+0000时，我得到一行。

aploetz@cqlsh:stackoverflow> SELECT * FROM temperature 
    WHERE weatherstation_id='1234ABCD' AND event_time > '2013-04-03 06:05:00+0000';

 weatherstation_id | event_time               | temperature
-------------------+--------------------------+-------------
          1234ABCD | 2013-04-03 07:01:00+0000 |         72F

(1 rows)

改变你的eventime >部分，将GMT偏移量包含在+0000中，你应该看到预期的结果。

如何让cassandra正确过滤？

1 个答案: