Cassandra

how-cass-data-is-saved.json

Reference:
https://opensourceconnections.com/blog/2013/07/24/understanding-how-cql3-maps-to-cassandras-internal-data-structure-sets-lists-and-maps/


// Column-Family
-----------------------------------------------------------------------------------------------
ID         Last    First   Bonus
 1          Doe     John    8000
 2          Smith   Jane    4000
 3          Beck    Sam     1000

Cassandra is a partitioned row store. Rows are organized into tables with a required primary key.
Partitioning means that Cassandra can distribute your data across multiple machines in an application-transparent matter. 
Cassandra will automatically repartition as machines are added and removed from the cluster.
Row store means that like relational databases, Cassandra organizes data by rows and columns.

In a row-oriented database management system, the data would be stored like this: 
1,Doe,John,8000;2,Smith,Jane,4000;3,Beck,Sam,1000;

In a column-oriented database management system, the data would be stored like this:
1,2,3;Doe,Smith,Beck;John,Jane,Sam;8000,4000,1000;

Cassandra is basically a column-family store
Cassandra would store the above data as, 
 "Bounses" : {
       row1 : { "ID":1, "Last":"Doe", "First":"John", "Bonus":8000},
       row2 : { "ID":2, "Last":"Smith", "First":"Jane", "Bonus":4000}
       ...
 }


// [ BASIC PRIMARY KEY ] RowKey: PARTITION_KEY_VALUE  column = FIELD_NAME  value = FIELD_VALUE
-----------------------------------------------------------------------------------------------
RowKey: 1
=> (column=, value=, timestamp=1374546754299000)
=> (column=field2, value=00000002, timestamp=1374546754299000)
=> (column=field3, value=00000003, timestamp=1374546754299000)


// [ COMPOSITE PRIMARY KEY ] RowKey: PARTITION_KEY_VALUE  
// column = CLUSTERING_KEY_VALUE:FIELD_NAME  value = FIELD_VALUE
-----------------------------------------------------------------------------------------------
RowKey: softwaredoug
=> (column=2013-07-13 08:21:54-0400:, value=, timestamp=1374673155373000)
=> (column=2013-07-13 08:21:54-0400:lat, value=4218a5e3, timestamp=1374673155373000)
=> (column=2013-07-13 08:21:54-0400:long, value=c29d1917, timestamp=1374673155373000)
=> (column=2013-07-13 08:21:54-0400:tweet, value=486176696e67206368657374207061696e2e, timestamp=1374673155373000)
=> (column=2013-07-21 12:15:27-0400:, value=, timestamp=1374673155407000)
=> (column=2013-07-21 12:15:27-0400:lat, value=42185f3b, timestamp=1374673155407000)
=> (column=2013-07-21 12:15:27-0400:long, value=c29d2560, timestamp=1374673155407000)
=> (column=2013-07-21 12:15:27-0400:tweet, value=53706565646f2073656c662073686f742e, timestamp=1374673155407000)


// [ MORE COMPOSITE PRIMARY KEY ] RowKey: PARTITION_KEY[1]_VALUE:PARTITION_KEY[2]_VALUE  
// column = CLUSTERING_KEY[1]_VALUE:CLUSTERING_KEY[2]_VALUE:FIELD_NAME  value = FIELD_VALUE
-----------------------------------------------------------------------------------------------
RowKey: partitionVal1:partitionVal2
=> (column=clusterVal1:clusterVal2:, value=, timestamp=1374630892473000)
=> (column=clusterVal1:clusterVal2:normalfield1, value=6e6f726d616c56616c31, timestamp=1374630892473000)
=> (column=clusterVal1:clusterVal2:normalfield2, value=6e6f726d616c56616c32, timestamp=1374630892473000)


// [ MAP ] column = MAP_FIELD_NAME:KEY  value = VALUE_OF_KEY
-----------------------------------------------------------------------------------------------
RowKey: scott
=> (column=, value=, timestamp=1374684062860000)
=> (column=phonenumbers:bill, value='555-7382', timestamp=1374684062860000)
=> (column=phonenumbers:jane, value='555-8743', timestamp=1374684062860000)
=> (column=phonenumbers:patricia, value='555-4326', timestamp=1374684062860000)


// [ LIST ] column = LIST_FIELD_NAME:UUID  value = FIELD_VALUE
// UUIDs are maintained to keep the entries in order, inserts are fast, deletes are slow(scan). 
-----------------------------------------------------------------------------------------------
RowKey: john
=> (column=, value=, timestamp=1374687324950000)
=> (column=friends:26017c10f48711e2801fdf9895e5d0f8, value='doug', timestamp=1374687206993000)
=> (column=friends:26017c11f48711e2801fdf9895e5d0f8, value='patricia', timestamp=1374687206993000)
=> (column=friends:26017c12f48711e2801fdf9895e5d0f8, value='scott', timestamp=1374687206993000)
=> (column=friends:6c504b60f48711e2801fdf9895e5d0f8, value='matt', timestamp=1374687324950000)
=> (column=friends:6c504b61f48711e2801fdf9895e5d0f8, value='eric', timestamp=1374687324950000)


// [ SET ] column = SET_FIELD_NAME:VALUE  value = EMPTY
-----------------------------------------------------------------------------------------------
RowKey: john
=> (column=, value=, timestamp=1374688135443000)
=> (column=friends:'doug', value=, timestamp=1374688108307000)
=> (column=friends:'eric', value=, timestamp=1374688135443000)
=> (column=friends:'matt', value=, timestamp=1374688135443000)