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From "Ganza, Ivan" <>
Subject Cassandra upgrade to 1.1.1 resulted in slow query issue
Date Wed, 13 Jun 2012 18:05:07 GMT

We have recently introduced Cassandra at the Globe and Mail here in Toronto, Canada.  We are
processing and storing the North American stock-market feed.  We have found it to work very
quickly and things have been looking very good.

Recently we upgraded to version 1.1.1 and then we have noticed some issues occurring.

I will try to describe it for you here.  Basically one operation that we very often perform
and is very critical is the ability to 'get the latest quote'.  This would return to you the
latest Quote adjusted against exchange delay rules.  With Cassandra version 1.0.3 we could
get a Quote in around 2ms.  After update we are looking at time of at least 2-3 seconds.

The way we query the quote is using a REVERSED SuperSliceQuery  with start=now, end=00:00:00.000
(beginning of day) LIMITED to 1.

Our investigation leads us to suspect that, since upgrade, Cassandra seems to be reading the
sstable from disk even when we request a small range of day only 5 seconds back.  If you look
at the output below you can see that the query does NOT get slower as the lookback increases
from 5  sec, 60 sec, 15 min, 60 min, and 24 hours.

We also noticed that the query was very fast for the first five minutes of trading, apparently
until the first sstable was flushed to disk.  After that we go into query times of 1-2 seconds
or so.

Query time[lookback=5]:[1711ms]
Query time[lookback=60]:[1592ms]
Query time[lookback=900]:[1520ms]
Query time[lookback=3600]:[1294ms]
Query time[lookback=86400]:[1391ms]

We would really appreciate input or help on this.

Cassandra version: 1.1.1
Hector version: 1.0-1

public void testCassandraIssue() {
            try {
                  int[] seconds = new int[]{ 5, 60, 60 * 15, 60 * 60, 60 * 60 * 24};
                  for(int sec : seconds) {
                        DateTime start = new DateTime();
                        SuperSliceQuery<String, String, String, String> superSliceQuery
= HFactory.createSuperSliceQuery(keyspaceOperator, StringSerializer.get(), StringSerializer.get(),
StringSerializer.get(), StringSerializer.get());
                        superSliceQuery.setKey("101390" + "." + testFormatter.print(start));

                        long theStart = System.currentTimeMillis();
                        QueryResult<SuperSlice<String, String, String>> result
= superSliceQuery.execute();
                        long end = System.currentTimeMillis();
                        System.out.println("Query time[lookback=" + sec + "]:[" + (end - theStart)
+ "ms]");
            } catch(Exception e) {

create column family Quotes
    with column_type = Super
    and  comparator = BytesType
    and subcomparator = BytesType
    and keys_cached = 7000
    and rows_cached = 0
    and row_cache_save_period = 0
    and key_cache_save_period = 3600
    and memtable_throughput = 255
    and memtable_operations = 0.29
    AND compression_options={sstable_compression:SnappyCompressor, chunk_length_kb:64};


Ivan Ganza | Senior Developer | Information Technology
c: 647.701.6084 | e:

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