I have a queue-like table which is reading 75k Iive rows… and then only returning 500.
… I'm trying to figure out why this could be. Following this: http://www.datastax.com/dev/blog/cassandra-anti-patterns-queues-and-queue-like-datasets I BELIEVE that I'm doing everything right. Essentially my schema is: bucket: int sequence: long value: text… primary key( bucket, sequence ) … value is just a big chunk of html. sequence is a timestamp essentially. I have 100 buckets… and that's the partition key. So I can stick these buckets across 100 servers token ranges. The query is specified to only read values greater than a sequence value… I'm avoiding tombstone columns ("When you know where your live columns begin") by specifying the after parameter and setting gc_grace_seconds=0 … The query is essentially: SELECT * FROM content WHERE bucket=98 AND sequence>1403995838000000000 ORDER BY sequence ASC LIMIT 500; .. I got rid of the " ORDER BY sequence ASC " as a test and that didn't change anything. The main problem seems to be"Read 75568 live and 0 tombstones cells" … and I have NO idea why it's reading so many rows! I woud have hoped that cassandra would do a binary search of the row, find the column it needs, then read then next 500 sequentially. But that doesn't seem to be the case. Any thoughts? activity | timestamp | source | source_elapsed -----------------------------------------------------------------------------------------------------------------+--------------+-------------+---------------- execute_cql3_query | 12:17:49,886 | 10.24.23.94 | 0 Parsing SELECT * FROM content WHERE bucket=98 AND sequence>1403995838000000000 ORDER BY sequence ASC LIMIT 500; | 12:17:49,886 | 10.24.23.94 | 65 Preparing statement | 12:17:49,886 | 10.24.23.94 | 149 Row cache miss | 12:17:49,886 | 10.24.23.94 | 338 Executing single-partition query on content | 12:17:49,887 | 10.24.23.94 | 402 Acquiring sstable references | 12:17:49,887 | 10.24.23.94 | 464 Merging memtable tombstones | 12:17:49,887 | 10.24.23.94 | 514 Partition index with 35 entries found for sstable 156 | 12:17:49,888 | 10.24.23.94 | 2344 Seeking to partition beginning in data file | 12:17:49,888 | 10.24.23.94 | 2360 Key cache hit for sstable 155 | 12:17:49,889 | 10.24.23.94 | 3006 Seeking to partition beginning in data file | 12:17:49,889 | 10.24.23.94 | 3020 Skipped 0/2 non-slice-intersecting sstables, included 0 due to tombstones | 12:17:49,890 | 10.24.23.94 | 3577 Merging data from memtables and 2 sstables | 12:17:49,890 | 10.24.23.94 | 3602 Read 75568 live and 0 tombstoned cells | 12:17:50,777 | 10.24.23.94 | 890823 Read 501 live and 0 tombstoned cells | 12:17:51,055 | 10.24.23.94 | 1169184 Request complete | 12:17:51,069 | 10.24.23.94 | 1183383 -- Founder/CEO Spinn3r.com Location: *San Francisco, CA* blog: http://burtonator.wordpress.com … or check out my Google+ profile <https://plus.google.com/102718274791889610666/posts> <http://spinn3r.com>
