Need help understanding cfhistograms output

Question

We are using Scylla version 4.4.1-0.20210406.00da6b5e9

I am not able to understand that

How nodetool cfhistogram is showing more no of sstables touched than the number of sstables that are actually present according to cfstats?
Why nodetool cfhistogram is showing such a high number sstables? I even ran nodetool compact prior to this.

Table structure:

CREATE TABLE gauntlet_keyspace.user_match_mapping (
user_id bigint,
match_id bigint,
team_id bigint,
created_at timestamp,
team_detail text,
updated_at timestamp,
user_login text,
user_team_name text,
PRIMARY KEY (user_id, match_id, team_id)
) WITH CLUSTERING ORDER BY (match_id ASC, team_id ASC)
AND bloom_filter_fp_chance = 0.01
AND caching = {'keys': 'ALL', 'rows_per_partition': 'ALL'}
AND comment = ''
AND compaction = {'class': 'SizeTieredCompactionStrategy'}
AND compression = {'sstable_compression': 
'org.apache.cassandra.io.compress.LZ4Compressor'}
AND crc_check_chance = 1.0
AND dclocal_read_repair_chance = 0.0
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';

cfstats

Keyspace : gauntlet_keyspace
Read Count: 9861938
Read Latency: 0.00119595834003418 ms
Write Count: 0
Write Latency: NaN ms
Pending Flushes: 0
    Table: user_match_mapping
    SSTable count: 14
    SSTables in each level: [14/4]
    Space used (live): 51979706055
    Space used (total): 51979706055
    Space used by snapshots (total): 0
    Off heap memory used (total): 92586912
    SSTable Compression Ratio: 0.203467
    Number of partitions (estimate): 4328815
    Memtable cell count: 0
    Memtable data size: 0
    Memtable off heap memory used: 0
    Memtable switch count: 0
    Local read count: 9799345
    Local read latency: 1.178 ms
    Local write count: 0
    Local write latency: NaN ms
    Pending flushes: 0
    Percent repaired: 0.0
    Bloom filter false positives: 0
    Bloom filter false ratio: 0.00000
    Bloom filter space used: 6195424
    Bloom filter off heap memory used: 6195368
    Index summary off heap memory used: 86391544
    Compression metadata off heap memory used: 0
    Compacted partition minimum bytes: 771
    Compacted partition maximum bytes: 785939
    Compacted partition mean bytes: 63765
    Average live cells per slice (last five minutes): 0.0
    Maximum live cells per slice (last five minutes): 0
    Average tombstones per slice (last five minutes): 0.0
    Maximum tombstones per slice (last five minutes): 0
    Dropped Mutations: 0

cfhistograms

Percentile  SSTables     Write Latency      Read Latency    Partition Size        Cell Count
                                (micros)          (micros)           (bytes)
    50%             0.00              0.00           1065.50             14237                72
    75%             0.00              0.00           1286.50            105778               642
    95%       1469901.75              0.00           1706.15            219342              1109
    98%       9799345.00              0.00           1934.88            315852              1916
    99%       9799345.00              0.00           2067.69            379022              1916
    Min             0.00              0.00            554.00               771                 5
    Max       9799345.00              0.00           2202.00            785939              3973

Only this read query was done select * from gauntlet_keyspace.user_match_mapping where user_id=? and match_id=? and team_id=?;

Need help understanding cfhistograms output

0 Answers