Both tables use the default bloom_filter_fp_chance of 0.01 ...
CREATE TABLE ... (
a int,
b int,
bucket timestamp,
ts timeuuid,
c int,
...
PRIMARY KEY ((a, b, bucket), ts, c)
) WITH CLUSTERING ORDER BY (ts DESC, monitor ASC)
AND bloom_filter_fp_chance = 0.01
AND compaction = {'class':
'org.apache.cassandra.db.compaction.TimeWindowCompactionStrategy',
'compaction_window_size': '1', 'compaction_window_unit': 'DAYS',
'tombstone_threshold': '0.9', 'unchecked_tombstone_compaction':
'false'}
AND dclocal_read_repair_chance = 0.0
AND default_time_to_live = 63072000
AND gc_grace_seconds = 10800
...
AND read_repair_chance = 0.0
AND speculative_retry = 'NONE';
CREATE TABLE ... (
c int,
b int,
bucket timestamp,
ts timeuuid,
...
PRIMARY KEY ((c, b, bucket), ts)
) WITH CLUSTERING ORDER BY (ts DESC)
AND bloom_filter_fp_chance = 0.01
AND compaction = {'class':
'org.apache.cassandra.db.compaction.TimeWindowCompactionStrategy',
'compaction_window_size': '1', 'compaction_window_unit': 'DAYS',
'tombstone_threshold': '0.9', 'unchecked_tombstone_compaction':
'false'}
AND dclocal_read_repair_chance = 0.0
AND default_time_to_live = 63072000
AND gc_grace_seconds = 10800
...
AND read_repair_chance = 0.0
AND speculative_retry = 'NONE';
On Wed, Apr 17, 2019 at 12:25 PM Stefan Miklosovic <
[email protected]> wrote:
> What is your bloom_filter_fp_chance for either table? I guess it is
> bigger for the first one, bigger that number is between 0 and 1, less
> memory it will use (17 MiB against 54.9 Mib) which means more false
> positives you will get.
>
> On Wed, 17 Apr 2019 at 19:59, Martin Mačura <[email protected]> wrote:
> >
> > Hi,
> > I have a table with poor bloom filter false ratio:
> > SSTable count: 1223
> > Space used (live): 726.58 GiB
> > Number of partitions (estimate): 8592749
> > Bloom filter false positives: 35796352
> > Bloom filter false ratio: 0.68472
> > Bloom filter space used: 17.82 MiB
> > Compacted partition maximum bytes: 386857368
> >
> > It's a time series, TWCS compaction, window size 1 day, data partitioned
> in daily buckets, TTL 2 years.
> >
> > I have another table with a similar schema, but it is not affected for
> some reason:
> > SSTable count: 1114
> > Space used (live): 329.87 GiB
> > Number of partitions (estimate): 25460768
> > Bloom filter false positives: 156942
> > Bloom filter false ratio: 0.00010
> > Bloom filter space used: 54.9 MiB
> > Compacted partition maximum bytes: 20924300
> >
> > Thanks for any advice,
> >
> > Martin
>
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