cassandra阅读表现不好

时间：2017-04-07 07:25:30

标签： cassandra cql

我有一个表包含cassandra3.10中的8百万行数据。当我执行以下查询时：select max(glass_id) from poc.dream where time < '2017-04-01 00:00:00+0000' allow filtering; time属性是表的分区键，我选择的数据大小是7000万。但是我的阅读表现不好，花了2分钟才得到结果。

主键是PK（time，glass_id）;

跟踪日志的部分显示如下：

Preparing statement [Native-Transport-Requests-1] | 2017-04-07 14:58:55.598000 | 172.19.16.44 |            247 | 127.0.0.1 
Computing ranges to query [Native-Transport-Requests-1] | 2017-04-07 14:58:55.599000 | 172.19.16.44 |            771 | 127.0.0.1
RANGE_SLICE message received from /172.19.16.44 [MessagingService-Incoming-/172.19.16.44] | 2017-04-07 14:58:55.599000 | 172.19.20.89 |             40 | 127.0.0.1
Submitting range requests on 769 ranges with a concurrency of 1 (0.0 rows per range expected) [Native-Transport-Requests-1] | 2017-04-07 14:58:55.599000 | 172.19.16.44 |            862 | 127.0.0.1
Enqueuing request to /172.19.20.89 [Native-Transport-Requests-1] | 2017-04-07 14:58:55.599000 | 172.19.16.44 |            881 | 127.0.0.1
Submitted 1 concurrent range requests [Native-Transport-Requests-1] | 2017-04-07 14:58:55.599000 | 172.19.16.44 |            899 | 127.0.0.1
Sending RANGE_SLICE message to /172.19.20.89 [MessagingService-Outgoing-/172.19.20.89-Small] | 2017-04-07 14:58:55.599000 | 172.19.16.44 |            937 | 127.0.0.1
Executing seq scan across 0 sstables for (min(-9223372036854775808), max(-9222003595370030342)] [ReadStage-1] | 2017-04-07 14:58:55.600000 | 172.19.20.89 |            369 | 127.0.0.1
Read 0 live and 0 tombstone cells [ReadStage-1] | 2017-04-07 14:58:55.600000 | 172.19.20.89 |            517 | 127.0.0.1
Enqueuing response to /172.19.16.44 [ReadStage-1] | 2017-04-07 14:58:55.600000 | 172.19.20.89 |            575 | 127.0.0.1
Sending REQUEST_RESPONSE message to /172.19.16.44 [MessagingService-Outgoing-/172.19.16.44-Small] | 2017-04-07 14:58:55.600000 | 172.19.20.89 |            977 | 127.0.0.1
REQUEST_RESPONSE message received from /172.19.20.89 [MessagingService-Incoming-/172.19.20.89] | 2017-04-07 14:58:55.601000 | 172.19.16.44 |           3018 | 127.0.0.1
Processing response from /172.19.20.89 [RequestResponseStage-2] | 2017-04-07 14:58:55.601000 | 172.19.16.44 |           3090 | 127.0.0.1
Enqueuing request to /172.19.20.5 [Native-Transport-Requests-1] | 2017-04-07 14:58:55.601000 | 172.19.16.44 |           3168 | 127.0.0.1
Enqueuing request to /172.19.20.5 [Native-Transport-Requests-1] | 2017-04-07 14:58:55.601000 | 172.19.16.44 |           3198 | 127.0.0.1
Enqueuing request to /172.19.20.89 [Native-Transport-Requests-1] | 2017-04-07 14:58:55.601000 | 172.19.16.44 |           3210 | 127.0.0.1
Sending RANGE_SLICE message to /172.19.20.5 [MessagingService-Outgoing-/172.19.20.5-Small] | 2017-04-07 14:58:55.601000 | 172.19.16.44 |           3210 | 127.0.0.1
Enqueuing request to /172.19.20.5 [Native-Transport-Requests-1] | 2017-04-07 14:58:55.601001 | 172.19.16.44 |           3222 | 127.0.0.1
Enqueuing request to /172.19.20.89 [Native-Transport-Requests-1] | 2017-04-07 14:58:55.601001 | 172.19.16.44 |           3230 | 127.0.0.1
Sending RANGE_SLICE message to /172.19.20.89 [MessagingService-Outgoing-/172.19.20.89-Small] | 2017-04-07 14:58:55.601001 | 172.19.16.44 |           3232 | 127.0.0.1
Enqueuing request to /172.19.20.89 [Native-Transport-Requests-1] | 2017-04-07 14:58:55.601001 | 172.19.16.44 |           3240 | 127.0.0.1
Sending RANGE_SLICE message to /172.19.20.5 [MessagingService-Outgoing-/172.19.20.5-Small] | 2017-04-07 14:58:55.601001 | 172.19.16.44 |           3247 | 127.0.0.1
Enqueuing request to /172.19.20.5 [Native-Transport-Requests-1] | 2017-04-07 14:58:55.601001 | 172.19.16.44 |           3249 | 127.0.0.1
Enqueuing request to /172.19.20.89 [Native-Transport-Requests-1] | 2017-04-07 14:58:55.601001 | 172.19.16.44 |           3257 | 127.0.0.1
Enqueuing request to /172.19.20.5 [Native-Transport-Requests-1] | 2017-04-07 14:58:55.601001 | 172.19.16.44 |           3264 | 127.0.0.1
Sending RANGE_SLICE message to /172.19.20.5 [MessagingService-Outgoing-/172.19.20.5-Small] | 2017-04-07 14:58:55.601002 | 172.19.16.44 |           3267 | 127.0.0.1
Executing seq scan across 0 sstables for (max(-9153807552532774465), max(-9087147317664915466)] [ReadStage-2] | 2017-04-07 14:58:55.601002 | 172.19.16.44 |           3273 | 127.0.0.1
Enqueuing request to /172.19.20.89 [Native-Transport-Requests-1] | 2017-04-07 14:58:55.601002 | 172.19.16.44 |           3273 | 127.0.0.1
Sending RANGE_SLICE message to /172.19.20.89 [MessagingService-Outgoing-/172.19.20.89-Small] | 2017-04-07 14:58:55.601002 | 172.19.16.44 |           3274 | 127.0.0.1
Enqueuing request to /172.19.20.89 [Native-Transport-Requests-1] | 2017-04-07 14:58:55.601002 | 172.19.16.44 |           3285 | 127.0.0.1
Executing seq scan across 0 sstables for (max(-9072913252686483927), max(-9071905664525634895)] [ReadStage-4] | 2017-04-07 14:58:55.601002 | 172.19.16.44 |           3284 | 127.0.0.1
Sending RANGE_SLICE message to /172.19.20.5 [MessagingService-Outgoing-/172.19.20.5-Small] | 2017-04-07 14:58:55.601002 | 172.19.16.44 |           3290 | 127.0.0.1
Enqueuing request to /172.19.20.89 [Native-Transport-Requests-1] | 2017-04-07 14:58:55.601002 | 172.19.16.44 |           3294 | 127.0.0.1
Sending RANGE_SLICE message to /172.19.20.89 [MessagingService-Outgoing-/172.19.20.89-Small] | 2017-04-07 14:58:55.601002 | 172.19.16.44 |           3296 | 127.0.0.1
Enqueuing request to /172.19.20.89 [Native-Transport-Requests-1] | 2017-04-07 14:58:55.601002 | 172.19.16.44 |           3304 | 127.0.0.1
Sending RANGE_SLICE message to /172.19.20.5 [MessagingService-Outgoing-/172.19.20.5-Small] | 2017-04-07 14:58:55.601002 | 172.19.16.44 |           3307 | 127.0.0.1
Enqueuing request to /172.19.20.89 [Native-Transport-Requests-1] | 2017-04-07 14:58:55.601002 | 172.19.16.44 |           3313 | 127.0.0.1
Sending RANGE_SLICE message to /172.19.20.89 [MessagingService-Outgoing-/172.19.20.89-Small] | 2017-04-07 14:58:55.601003 | 172.19.16.44 |           3319 | 127.0.0.1
Enqueuing request to /172.19.20.5 [Native-Transport-Requests-1] | 2017-04-07 14:58:55.601003 | 172.19.16.44 |           3321 | 127.0.0.1
Read 0 live and 0 tombstone cells [ReadStage-4] | 2017-04-07 14:58:55.601003 | 172.19.16.44 |           3323 | 127.0.0.1
Read 0 live and 0 tombstone cells [ReadStage-2] | 2017-04-07 14:58:55.601003 | 172.19.16.44 |           3323 | 127.0.0.1

1 个答案:

答案 0 :(得分：3)

您在一个查询中做错了两件事。

首先：您没有指定分区键，因此cassandra需要在每个节点上执行查询

第二：您正在使用聚合方法max()，它扫描所有行（对于您的情况为70百万行），只是为了给您最大数量。

更改您的数据模型，而不是使用此类查询，以便您可以指定分区键并通过desc指定glass_id作为群集键顺序。

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