When I issue
$ nodetool compactionhistory
I get
. . . compacted_at bytes_in bytes_out rows_merged
. . . 1404936947592 8096 7211 {1:3, 3:1}
What does {1:3, 3:1} mean? The only documentation I can find is this which states
the number of partitions merged
which does not explain why multiple values and what the colon means.
So basically it means {tables:rows} for example {1:3, 3:1} means 3 rows were taken from one sstable (1:3) and 1 row taken from 3 (3:1) sstables, all to make the one sstable in that compaction operation.
I tried it out myself so here's an example, I hope this helps:
create keyspace and table:
cqlsh> create keyspace space1 WITH replication = {'class': 'SimpleStrategy', 'replication_factor': 1};
cqlsh> create TABLE space1.tb1 ( key text, val1 text, primary KEY (key));
cqlsh> INSERT INTO space1.tb1 (key, val1 ) VALUES ( 'key1','111');
cqlsh> INSERT INTO space1.tb1 (key, val1 ) VALUES ( 'key2','222');
cqlsh> INSERT INTO space1.tb1 (key, val1 ) VALUES ( 'key3','333');
cqlsh> INSERT INTO space1.tb1 (key, val1 ) VALUES ( 'key4','444');
cqlsh> INSERT INTO space1.tb1 (key, val1 ) VALUES ( 'key5','555');
cqlsh> exit
Now we flush to create the sstable
$ nodetool flush space1
We see that only one version of the table is created
$ sudo ls -lR /var/lib/cassandra/data/space1
/var/lib/cassandra/data/space1:
total 4
drwxr-xr-x. 2 cassandra cassandra 4096 Feb 3 12:51 tb1
/var/lib/cassandra/data/space1/tb1:
total 32
-rw-r--r--. 1 cassandra cassandra 43 Feb 3 12:51 space1-tb1-jb-1-CompressionInfo.db
-rw-r--r--. 1 cassandra cassandra 146 Feb 3 12:51 space1-tb1-jb-1-Data.db
-rw-r--r--. 1 cassandra cassandra 24 Feb 3 12:51 space1-tb1-jb-1-Filter.db
-rw-r--r--. 1 cassandra cassandra 90 Feb 3 12:51 space1-tb1-jb-1-Index.db
-rw-r--r--. 1 cassandra cassandra 4389 Feb 3 12:51 space1-tb1-jb-1-Statistics.db
-rw-r--r--. 1 cassandra cassandra 80 Feb 3 12:51 space1-tb1-jb-1-Summary.db
-rw-r--r--. 1 cassandra cassandra 79 Feb 3 12:51 space1-tb1-jb-1-TOC.txt
check the sstable2json we see our data
$ sudo -u cassandra /usr/bin/sstable2json /var/lib/cassandra/data/space1/tb1/space1-tb1-jb-1-Data.db
[
{"key": "6b657935","columns": [["","",1422967847005000], ["val1","555",1422967847005000]]},
{"key": "6b657931","columns": [["","",1422967817740000], ["val1","111",1422967817740000]]},
{"key": "6b657934","columns": [["","",1422967840622000], ["val1","444",1422967840622000]]},
{"key": "6b657933","columns": [["","",1422967832341000], ["val1","333",1422967832341000]]},
{"key": "6b657932","columns": [["","",1422967825116000], ["val1","222",1422967825116000]]}
]
At this point ‘notetool compactionhistory’ shows nothing for this table but lets run compact anyway to see what we get (scroll right)
$ nodetool compactionhistory | awk 'NR == 2 || /space1/'
id keyspace_name columnfamily_name compacted_at bytes_in bytes_out rows_merged
5725f890-aba4-11e4-9f73-351725b0ac5b space1 tb1 1422968305305 146 146 {1:5}
Now lets delete two rows, and flush
cqlsh> delete from space1.tb1 where key='key1';
cqlsh> delete from space1.tb1 where key='key2';
cqlsh> exit
$ nodetool flush space1
$ sudo ls -l /var/lib/cassandra/data/space1/tb1/
[sudo] password for datastax:
total 64
-rw-r--r--. 1 cassandra cassandra 43 Feb 3 12:58 space1-tb1-jb-2-CompressionInfo.db
-rw-r--r--. 1 cassandra cassandra 146 Feb 3 12:58 space1-tb1-jb-2-Data.db
-rw-r--r--. 1 cassandra cassandra 336 Feb 3 12:58 space1-tb1-jb-2-Filter.db
-rw-r--r--. 1 cassandra cassandra 90 Feb 3 12:58 space1-tb1-jb-2-Index.db
-rw-r--r--. 1 cassandra cassandra 4393 Feb 3 12:58 space1-tb1-jb-2-Statistics.db
-rw-r--r--. 1 cassandra cassandra 80 Feb 3 12:58 space1-tb1-jb-2-Summary.db
-rw-r--r--. 1 cassandra cassandra 79 Feb 3 12:58 space1-tb1-jb-2-TOC.txt
-rw-r--r--. 1 cassandra cassandra 43 Feb 3 13:02 space1-tb1-jb-3-CompressionInfo.db
-rw-r--r--. 1 cassandra cassandra 49 Feb 3 13:02 space1-tb1-jb-3-Data.db
-rw-r--r--. 1 cassandra cassandra 16 Feb 3 13:02 space1-tb1-jb-3-Filter.db
-rw-r--r--. 1 cassandra cassandra 36 Feb 3 13:02 space1-tb1-jb-3-Index.db
-rw-r--r--. 1 cassandra cassandra 4413 Feb 3 13:02 space1-tb1-jb-3-Statistics.db
-rw-r--r--. 1 cassandra cassandra 80 Feb 3 13:02 space1-tb1-jb-3-Summary.db
-rw-r--r--. 1 cassandra cassandra 79 Feb 3 13:02 space1-tb1-jb-3-TOC.txt
Lets check the tables contents
$ sudo -u cassandra /usr/bin/sstable2json /var/lib/cassandra/data/space1/tb1/space1-tb1-jb-2-Data.db
[
{"key": "6b657935","columns": [["","",1422967847005000], ["val1","555",1422967847005000]]},
{"key": "6b657931","columns": [["","",1422967817740000], ["val1","111",1422967817740000]]},
{"key": "6b657934","columns": [["","",1422967840622000], ["val1","444",1422967840622000]]},
{"key": "6b657933","columns": [["","",1422967832341000], ["val1","333",1422967832341000]]},
{"key": "6b657932","columns": [["","",1422967825116000], ["val1","222",1422967825116000]]}
]
$ sudo -u cassandra /usr/bin/sstable2json /var/lib/cassandra/data/space1/tb1/space1-tb1-jb-3-Data.db
[
{"key": "6b657931","metadata": {"deletionInfo": {"markedForDeleteAt":1422968551313000,"localDeletionTime":1422968551}},"columns": []},
{"key": "6b657932","metadata": {"deletionInfo": {"markedForDeleteAt":1422968553322000,"localDeletionTime":1422968553}},"columns": []}
]
Now lets compact
$ nodetool compact space1
Only one stable now as expected
$ sudo ls -l /var/lib/cassandra/data/space1/tb1/
total 32
-rw-r--r--. 1 cassandra cassandra 43 Feb 3 13:05 space1-tb1-jb-4-CompressionInfo.db
-rw-r--r--. 1 cassandra cassandra 133 Feb 3 13:05 space1-tb1-jb-4-Data.db
-rw-r--r--. 1 cassandra cassandra 656 Feb 3 13:05 space1-tb1-jb-4-Filter.db
-rw-r--r--. 1 cassandra cassandra 90 Feb 3 13:05 space1-tb1-jb-4-Index.db
-rw-r--r--. 1 cassandra cassandra 4429 Feb 3 13:05 space1-tb1-jb-4-Statistics.db
-rw-r--r--. 1 cassandra cassandra 80 Feb 3 13:05 space1-tb1-jb-4-Summary.db
-rw-r--r--. 1 cassandra cassandra 79 Feb 3 13:05 space1-tb1-jb-4-TOC.txt
Now lets check the contents of the new stable we can see the tombstones
$ sudo -u cassandra /usr/bin/sstable2json /var/lib/cassandra/data/space1/tb1/space1-tb1-jb-4-Data.db
[
{"key": "6b657935","columns": [["","",1422967847005000], ["val1","555",1422967847005000]]},
{"key": "6b657931","metadata": {"deletionInfo": {"markedForDeleteAt":1422968551313000,"localDeletionTime":1422968551}},"columns": []},
{"key": "6b657934","columns": [["","",1422967840622000], ["val1","444",1422967840622000]]},
{"key": "6b657933","columns": [["","",1422967832341000], ["val1","333",1422967832341000]]},
{"key": "6b657932","metadata": {"deletionInfo": {"markedForDeleteAt":1422968553322000,"localDeletionTime":1422968553}},"columns": []}
]
Finally lets check compaction history (scroll right)
$ nodetool compactionhistory | awk 'NR == 2 || /space1/'
id keyspace_name columnfamily_name compacted_at bytes_in bytes_out rows_merged
5725f890-aba4-11e4-9f73-351725b0ac5b space1 tb1 1422968305305 146 146 {1:5}
46112600-aba5-11e4-9f73-351725b0ac5b space1 tb1 1422968706144 195 133 {1:3, 2:2}
