Apache Canssandra 2.2.5版
我们有一个cassandra集群，有10个备注。总数据大小为10TB。有一个非常大的桌面收件箱。这个表上的几个查询非常慢。 95％的查询可以在10ms内返回。但很少有查询读取超时（＆gt; 5s）。
收件箱表的架构是：
CREATE TABLE feeds.inbox (
owner_id bigint,
activity_id bigint,
insert_time timestamp,
PRIMARY KEY (owner_id, activity_id)
) WITH CLUSTERING ORDER BY (activity_id ASC)
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.LeveledCompactionStrategy'}
AND compression = {'sstable_compression': 'org.apache.cassandra.io.compress.LZ4Compressor'}
AND dclocal_read_repair_chance = 0.1
AND default_time_to_live = 0
AND gc_grace_seconds = 864000
AND max_index_interval = 2048
AND memtable_flush_period_in_ms = 0
AND min_index_interval = 128
AND read_repair_chance = 0.0
AND speculative_retry = '99.0PERCENTILE';
其中一个慢查询就是：
select activity_id, insert_time FROM inbox WHERE owner_id=87500212012802048 ORDER BY activity_id desc;
此分区只有44行（owner_id = 87500212012802048）。
查询跟踪：
activity | timestamp | source | source_elapsed
--------------------------------------------------------------------------------------------------------------------------------------+----------------------------+--------------+----------------
Execute CQL3 query | 2016-05-04 20:58:53.970000 | 172.31.8.188 | 0
Parsing select activity_id, insert_time FROM inbox WHERE owner_id=87500212012802048 ORDER BY activity_id desc; [SharedPool-Worker-2] | 2016-05-04 20:58:53.971000 | 172.31.8.188 | 147
Preparing statement [SharedPool-Worker-2] | 2016-05-04 20:58:53.971000 | 172.31.8.188 | 213
reading data from /172.31.8.187 [SharedPool-Worker-2] | 2016-05-04 20:58:53.971000 | 172.31.8.188 | 369
Sending READ message to /172.31.8.187 [MessagingService-Outgoing-/172.31.8.187] | 2016-05-04 20:58:53.971000 | 172.31.8.188 | 739
READ message received from /172.31.8.188 [MessagingService-Incoming-/172.31.8.188] | 2016-05-04 20:58:53.972000 | 172.31.8.187 | 19
Executing single-partition query on inbox [SharedPool-Worker-4] | 2016-05-04 20:58:53.972000 | 172.31.8.187 | 350
Acquiring sstable references [SharedPool-Worker-4] | 2016-05-04 20:58:53.972000 | 172.31.8.187 | 372
Merging memtable tombstones [SharedPool-Worker-4] | 2016-05-04 20:58:53.972000 | 172.31.8.187 | 414
Bloom filter allows skipping sstable 353339 [SharedPool-Worker-4] | 2016-05-04 20:58:53.972000 | 172.31.8.187 | 446
Key cache hit for sstable 353313 [SharedPool-Worker-4] | 2016-05-04 20:58:53.972000 | 172.31.8.187 | 467
Seeking to partition indexed section in data file [SharedPool-Worker-4] | 2016-05-04 20:58:53.972001 | 172.31.8.187 | 475
Bloom filter allows skipping sstable 352862 [SharedPool-Worker-4] | 2016-05-04 20:58:53.973000 | 172.31.8.187 | 590
Key cache hit for sstable 352122 [SharedPool-Worker-4] | 2016-05-04 20:58:53.973000 | 172.31.8.187 | 612
Seeking to partition indexed section in data file [SharedPool-Worker-4] | 2016-05-04 20:58:53.973000 | 172.31.8.187 | 621
Key cache hit for sstable 345513 [SharedPool-Worker-4] | 2016-05-04 20:58:53.973000 | 172.31.8.187 | 779
Seeking to partition indexed section in data file [SharedPool-Worker-4] | 2016-05-04 20:58:53.973000 | 172.31.8.187 | 820
Skipped 0/5 non-slice-intersecting sstables, included 0 due to tombstones [SharedPool-Worker-4] | 2016-05-04 20:58:53.973000 | 172.31.8.187 | 837
Merging data from memtables and 3 sstables [SharedPool-Worker-4] | 2016-05-04 20:58:53.973001 | 172.31.8.187 | 848
Read 44 live and 0 tombstone cells [SharedPool-Worker-4] | 2016-05-04 20:58:57.546000 | 172.31.8.187 | 574196
Enqueuing response to /172.31.8.188 [SharedPool-Worker-4] | 2016-05-04 20:58:57.549000 | 172.31.8.187 | 577130
Sending REQUEST_RESPONSE message to /172.31.8.188 [MessagingService-Outgoing-/172.31.8.188] | 2016-05-04 20:58:57.551000 | 172.31.8.187 | 579411
REQUEST_RESPONSE message received from /172.31.8.187 [MessagingService-Incoming-/172.31.8.187] | 2016-05-04 20:58:57.557000 | 172.31.8.188 | 586750
Processing response from /172.31.8.187 [SharedPool-Worker-4] | 2016-05-04 20:58:57.557000 | 172.31.8.188 | 586930
Request complete | 2016-05-04 20:58:57.560568 | 172.31.8.188 | 590568
我们可以看到步骤＆＃39; Read 44 live和0 tombstone cells [SharedPool-Worker-4]＆＃39;需要50多岁！为什么查询速度太慢，尽管此分区中只有44行。
当我将群集密钥查询顺序更改为asc时，查询会增加一点，对于在线功能来说仍然太慢。
activity | timestamp | source | source_elapsed
-------------------------------------------------------------------------------------------------------------------------------------+----------------------------+--------------+----------------
Execute CQL3 query | 2016-05-04 21:19:29.275000 | 172.31.8.188 | 0
Parsing select activity_id, insert_time FROM inbox WHERE owner_id=87500212012802048 ORDER BY activity_id asc; [SharedPool-Worker-2] | 2016-05-04 21:19:29.275000 | 172.31.8.188 | 96
Preparing statement [SharedPool-Worker-2] | 2016-05-04 21:19:29.275000 | 172.31.8.188 | 150
Executing single-partition query on inbox [SharedPool-Worker-3] | 2016-05-04 21:19:29.275000 | 172.31.8.188 | 393
Acquiring sstable references [SharedPool-Worker-3] | 2016-05-04 21:19:29.275000 | 172.31.8.188 | 419
Merging memtable tombstones [SharedPool-Worker-3] | 2016-05-04 21:19:29.275000 | 172.31.8.188 | 450
Partition index lookup allows skipping sstable 324509 [SharedPool-Worker-3] | 2016-05-04 21:19:29.275001 | 172.31.8.188 | 510
Key cache hit for sstable 324457 [SharedPool-Worker-3] | 2016-05-04 21:19:29.275001 | 172.31.8.188 | 534
Seeking to partition beginning in data file [SharedPool-Worker-3] | 2016-05-04 21:19:29.275001 | 172.31.8.188 | 546
Key cache hit for sstable 324018 [SharedPool-Worker-3] | 2016-05-04 21:19:29.275001 | 172.31.8.188 | 640
Seeking to partition beginning in data file [SharedPool-Worker-3] | 2016-05-04 21:19:29.275001 | 172.31.8.188 | 685
Key cache hit for sstable 321829 [SharedPool-Worker-3] | 2016-05-04 21:19:29.276000 | 172.31.8.188 | 899
Seeking to partition beginning in data file [SharedPool-Worker-3] | 2016-05-04 21:19:29.276000 | 172.31.8.188 | 926
Key cache hit for sstable 314770 [SharedPool-Worker-3] | 2016-05-04 21:19:29.276000 | 172.31.8.188 | 1171
Seeking to partition beginning in data file [SharedPool-Worker-3] | 2016-05-04 21:19:29.276000 | 172.31.8.188 | 1199
Skipped 0/5 non-slice-intersecting sstables, included 0 due to tombstones [SharedPool-Worker-3] | 2016-05-04 21:19:29.276000 | 172.31.8.188 | 1456
Merging data from memtables and 4 sstables [SharedPool-Worker-3] | 2016-05-04 21:19:29.276000 | 172.31.8.188 | 1488
Read 44 live and 0 tombstone cells [SharedPool-Worker-3] | 2016-05-04 21:19:29.440000 | 172.31.8.188 | 165319
Request complete | 2016-05-04 21:19:29.448062 | 172.31.8.188 | 173062
答案 0 :(得分：0)
从跟踪日志中，我们可以看到这44行存储在4个sstables中。
合并来自memtables和4个sstables的数据
您可以尝试压缩inbox列系列吗？这应该减少阅读时间。
但我担心这对情况没有帮助。
合并来自memtables和4个sstables的数据[SharedPool-Worker-3] | 1488
阅读44个实时和0个墓碑单元格[SharedPool-Worker-3] | 165319
您可以附加Cassnadra日志以供进一步检查。似乎其他一些过程在合并之后和阅读之前花了很多时间。