SAI indexing with collections

SAI supports collections of type map, list, and set. Collections allow you to group and store data together in a column.

In a relational database, a grouping such as a user’s multiple email addresses is achieved via many-to-one joined relationship between (for example) a user table and an email table. DSE avoids joins between two tables by storing the user’s email addresses in a collection column in the user table. Each collection specifies the data type of the data held.

A collection is appropriate if the data for collection storage is limited. If the data has unbounded growth potential, like messages sent or sensor events registered every second, do not use collections. Instead, use a table with a compound primary key where data is stored in the clustering columns.

In CQL queries of database tables with SAI indexes, the CONTAINS clauses are supported with, and specific to:

  • SAI collection maps with keys, values, and entries

  • SAI collections with list and set types

Using the set type

This example uses the following table and index:

CREATE TABLE IF NOT EXISTS cycling.cyclist_career_teams (
  id UUID PRIMARY KEY,
  lastname text,
  teams set<text>
);
CREATE CUSTOM INDEX teams_idx 
    ON cycling.cyclist_career_teams (teams) 
    USING 'StorageAttachedIndex';

An index is created on the set column teams in the cyclist_career_teams table.

Query with CONTAINS from the set teams column:

  • CQL

  • Result

SELECT * FROM cycling.cyclist_career_teams 
    WHERE teams CONTAINS 'Rabobank-Liv Giant';
 id                                   | lastname | teams
--------------------------------------+----------+------------------------------------------------------------------------------------------------------
 5b6962dd-3f90-4c93-8f61-eabfa4a803e2 |      VOS | {'Nederland bloeit', 'Rabobank Women Team', 'Rabobank-Liv Giant', 'Rabobank-Liv Woman Cycling Team'}

Using the list type

This example uses the following table and index:

CREATE TABLE IF NOT EXISTS cycling.upcoming_calendar (
  year int,
  month int,
  events list<text>,
  PRIMARY KEY (year, month)
);
CREATE CUSTOM INDEX events_idx 
    ON cycling.upcoming_calendar (events) 
    USING 'StorageAttachedIndex';

An index is created on the list column events in the upcoming_calendar table.

Query with CONTAINS from the list events column:

  • CQL

  • Result

SELECT * FROM cycling.upcoming_calendar 
    WHERE events CONTAINS 'Criterium du Dauphine';
 year | month | events
------+-------+-----------------------------------------------
 2015 |     6 | ['Criterium du Dauphine', 'Tour de Sui\nsse']

A slightly more complex query selects rows that either contain a particular event or have a particular month date:

  • CQL

  • Result

SELECT * FROM cycling.upcoming_calendar
    WHERE 
        events CONTAINS 'Criterium du Dauphine' 
        OR month = 7;
 year | month | events
------+-------+-----------------------------------------------
 2015 |     6 | ['Criterium du Dauphine', 'Tour de Sui\nsse']
 2015 |     7 |                            ['Tour de France']

Using the map type

This example uses the following table and indexes:

CREATE TABLE IF NOT EXISTS cycling.cyclist_teams (
  id uuid PRIMARY KEY,
  firstname text,
  lastname text,
  teams map<int, text>
);

// Create an index on a map key to find all cyclist/team combos for a year 
CREATE INDEX IF NOT EXISTS team_year_keys_idx
ON cycling.cyclist_teams ( KEYS (teams) );

// Create an index on a map key to find all cyclist/team combos for a year 
CREATE INDEX IF NOT EXISTS team_year_values_idx
ON cycling.cyclist_teams ( VALUES (teams) );

// Create an index on a map key to find all cyclist/team combos for a year 
CREATE INDEX IF NOT EXISTS team_year_entries_idx
ON cycling.cyclist_teams ( ENTRIES (teams) );

Indexes created on the map column teams in the cyclist_career_teams table target the keys, values, and full entries of the column data.

Query with KEYS from the map teams column:

  • CQL

  • Result

SELECT * FROM cyclist_teams WHERE teams CONTAINS KEY 2014;
 id                                   | firstname | lastname   | teams
--------------------------------------+-----------+------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------
 cb07baad-eac8-4f65-b28a-bddc06a0de23 | Elizabeth | ARMITSTEAD | {2011: 'Team Garmin - Cervelo', 2012: 'AA Drink - Leontien.nl', 2013: 'Boels:Dolmans Cycling Team', 2014: 'Boels:Dolmans Cycling Team', 2015: 'Boels:Dolmans Cycling Team'}
 5b6962dd-3f90-4c93-8f61-eabfa4a803e2 |  Marianne |        VOS |                                                                                          {2014: 'Rabobank-Liv Woman Cycling Team', 2015: 'Rabobank-Liv Woman Cycling Team'}

Query a value from the map teams column, noting that only the keyword CONTAINS is included:

  • CQL

  • Result

SELECT * FROM cyclist_teams WHERE teams CONTAINS 'Team Garmin - Cervelo';
 id                                   | firstname | lastname   | teams
--------------------------------------+-----------+------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------
 cb07baad-eac8-4f65-b28a-bddc06a0de23 | Elizabeth | ARMITSTEAD | {2011: 'Team Garmin - Cervelo', 2012: 'AA Drink - Leontien.nl', 2013: 'Boels:Dolmans Cycling Team', 2014: 'Boels:Dolmans Cycling Team', 2015: 'Boels:Dolmans Cycling Team'}

Query entries from the map teams column, noting the difference in the WHERE clause:

  • CQL

  • Result

SELECT * FROM cyclist_teams 
WHERE 
    teams[2014] = 'Boels:Dolmans Cycling Team' 
    AND teams[2015] = 'Boels:Dolmans Cycling Team';
 id                                   | firstname | lastname   | teams
--------------------------------------+-----------+------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------
 cb07baad-eac8-4f65-b28a-bddc06a0de23 | Elizabeth | ARMITSTEAD | {2011: 'Team Garmin - Cervelo', 2012: 'AA Drink - Leontien.nl', 2013: 'Boels:Dolmans Cycling Team', 2014: 'Boels:Dolmans Cycling Team', 2015: 'Boels:Dolmans Cycling Team'}

This example looks for a row where two entries are present in the map teams column.

For more information, see:

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