Schema Metadata

Ruby Driver allows inspecting schema metadata

Background

Given: a running cassandra cluster

Getting keyspace metadata

Given

the following schema:

CREATE KEYSPACE simplex WITH replication = {'class': 'SimpleStrategy', 'replication_factor': 3};

And

the following example:

require 'cassandra'

cluster = Cassandra.cluster

ks_meta = cluster.keyspace('simplex')
puts "Name: #{ks_meta.name}"
puts "Replication class: #{ks_meta.replication.klass}"
puts "Replication factor: #{ks_meta.replication.options['replication_factor'].to_i}"
puts "Durable writes?: #{ks_meta.durable_writes?}"
puts "# tables: #{ks_meta.tables.size}"

puts ""
puts ks_meta.to_cql

When

it is executed

Then

its output should contain:

Name: simplex
Replication class: SimpleStrategy
Replication factor: 3
Durable writes?: true
# tables: 0

CREATE KEYSPACE simplex WITH replication = {'class': 'SimpleStrategy', 'replication_factor': '3'} AND durable_writes = true;

Getting table metadata

Given

the following schema:

CREATE KEYSPACE simplex WITH replication = {'class': 'SimpleStrategy', 'replication_factor': 3};
CREATE TABLE simplex.users (user_id bigint, first text, last text, age int, PRIMARY KEY (user_id, last))

And

the following example:

require 'cassandra'

cluster = Cassandra.cluster

table_meta = cluster.keyspace('simplex').table('users')
puts "Name: #{table_meta.name}"
puts "Keyspace: #{table_meta.keyspace.name}"
puts "Partition key: #{table_meta.partition_key[0].name}"
puts "Clustering column: #{table_meta.clustering_columns[0].name}"
puts "Clustering order: #{table_meta.clustering_order.first}"
puts "Num columns: #{table_meta.columns.size}"

puts ""
puts table_meta.to_cql

When

it is executed

Then

its output should contain:

Name: users
Keyspace: simplex
Partition key: user_id
Clustering column: last
Clustering order: asc
Num columns: 4

CREATE TABLE simplex."users" (
  user_id bigint,
  last text,
  age int,
  first text,
  PRIMARY KEY (user_id, last)
)

Getting index metadata

Given

the following schema:

CREATE KEYSPACE simplex WITH replication = {'class': 'SimpleStrategy', 'replication_factor': 3};
CREATE TABLE simplex.test_table (a int primary key, b int);
CREATE INDEX ind1 ON simplex.test_table (b);

And

the following example:

require 'cassandra'

cluster = Cassandra.cluster

index = cluster.keyspace('simplex').table('test_table').index('ind1')
puts index.to_cql

puts ""
puts "Name: #{index.name}"
puts "Table name: #{index.table.name}"
puts "Kind: #{index.kind}"
puts "Target: #{index.target}"

When

it is executed

Then

its output should contain:

CREATE INDEX "ind1" ON simplex.test_table (b);

Name: ind1
Table name: test_table
Kind: composites
Target: b

since cassadra v3.0

Getting index metadata on full collections

Given

the following schema:

CREATE KEYSPACE simplex WITH replication = {'class': 'SimpleStrategy', 'replication_factor': 3};
CREATE TABLE simplex.test_table (a int PRIMARY KEY, b frozen<map<text, text>>);
CREATE INDEX ind1 ON simplex.test_table (full(b));

And

the following example:

require 'cassandra'

cluster = Cassandra.cluster

index = cluster.keyspace('simplex').table('test_table').index('ind1')
puts index.to_cql

puts ""
puts "Name: #{index.name}"
puts "Table name: #{index.table.name}"
puts "Kind: #{index.kind}"
puts "Target: #{index.target}"

When

it is executed

Then

its output should contain:

CREATE INDEX "ind1" ON simplex.test_table (full(b));

Name: ind1
Table name: test_table
Kind: composites
Target: full(b)

since cassadra v3.0

Getting multiple index metadata on same column

Given

the following schema:

CREATE KEYSPACE simplex WITH replication = {'class': 'SimpleStrategy', 'replication_factor': 3};
CREATE TABLE simplex.test_table (a int PRIMARY KEY, b map<text, text>);
CREATE INDEX ind1 ON simplex.test_table (keys(b));
CREATE INDEX ind2 ON simplex.test_table (values(b));

And

the following example:

require 'cassandra'

cluster = Cassandra.cluster

index = cluster.keyspace('simplex').table('test_table').index('ind1')
puts index.to_cql

puts ""
puts "Name: #{index.name}"
puts "Target: #{index.target}"

puts ""
index = cluster.keyspace('simplex').table('test_table').index('ind2')
puts index.to_cql

puts ""
puts "Name: #{index.name}"
puts "Target: #{index.target}"

When

it is executed

Then

its output should contain:

CREATE INDEX "ind1" ON simplex.test_table (keys(b));

Name: ind1
Target: keys(b)

CREATE INDEX "ind2" ON simplex.test_table (values(b));

Name: ind2
Target: values(b)

since cassadra v2.1

Getting user-defined type metadata

Given

the following schema:

CREATE KEYSPACE simplex WITH replication = {'class': 'SimpleStrategy', 'replication_factor': 3};
CREATE TYPE simplex.address (street text, zipcode int);
CREATE TYPE simplex.check_in (
  location frozen <address>,
  time timestamp,
  data frozen <tuple<int, text, float>>
);
CREATE TABLE simplex.users (id int PRIMARY KEY, location frozen<address>);

And

the following example:

require 'cassandra'

cluster = Cassandra.cluster

cluster.keyspace('simplex').each_type do |type|
  puts type.to_cql
end

When

it is executed

Then

its output should contain:

CREATE TYPE simplex.address (
  street text,
  zipcode int
);
CREATE TYPE simplex.check_in (
  location frozen <address>,
  time timestamp,
  data frozen <tuple<int, text, float>>
);

since cassadra v2.2

Getting user-defined functions and metadata

Given

the following schema:

CREATE KEYSPACE simplex WITH replication = {'class': 'SimpleStrategy', 'replication_factor': 3};
CREATE OR REPLACE FUNCTION simplex.fLog(input double)
  CALLED ON NULL INPUT
  RETURNS double
  LANGUAGE java
  AS 'return Double.valueOf(Math.log(input.doubleValue()));'

And

the following example:

require 'cassandra'
include Cassandra::Types

cluster = Cassandra.cluster

puts cluster.keyspace('simplex').function('fLog', double).to_cql

function = cluster.keyspace('simplex').function('fLog', double)
puts ""
puts "Name: #{function.name}"
puts "Language: #{function.language}"
puts "Return type: #{function.type}"
puts "Called on null?: #{function.called_on_null?}"
puts "Argument 'input'?: #{function.has_argument?("input")}"
function.each_argument { |arg| puts "Argument type: #{arg.type}" }

When

it is executed

Then

its output should contain:

CREATE FUNCTION simplex.flog(input double)
  CALLED ON NULL INPUT
  RETURNS double
  LANGUAGE java
  AS $$return Double.valueOf(Math.log(input.doubleValue()));$$;

Name: flog
Language: java
Return type: double
Called on null?: true
Argument 'input'?: true
Argument type: double

since cassadra v2.2

Getting user-defined aggregates and metadata

Given

the following schema:

CREATE KEYSPACE simplex WITH replication = {'class': 'SimpleStrategy', 'replication_factor': 3};
CREATE OR REPLACE FUNCTION simplex.avgState(state tuple<int, bigint>, val int)
  CALLED ON NULL INPUT
  RETURNS tuple<int, bigint>
  LANGUAGE java
  AS 'if (val !=null) { state.setInt(0, state.getInt(0)+1); state.setLong(1, state.getLong(1)+val.intValue()); } return state;';
CREATE OR REPLACE FUNCTION simplex.avgFinal(state tuple<int, bigint>)
  CALLED ON NULL INPUT
  RETURNS double
  LANGUAGE java
  AS 'double r = 0; if (state.getInt(0) == 0) return null; r = state.getLong(1); r/= state.getInt(0); return Double.valueOf(r);';
CREATE OR REPLACE AGGREGATE simplex.average(int)
  SFUNC avgState
  STYPE tuple<int, bigint>
  FINALFUNC avgFinal
  INITCOND (0, 0);

And

the following example:

require 'cassandra'
include Cassandra::Types

cluster = Cassandra.cluster

aggregate = cluster.keyspace('simplex').aggregate('average', int)
puts aggregate.to_cql
puts ""
puts "Name: #{aggregate.name}"
puts "Return type: #{aggregate.type}"
puts "Argument type: #{aggregate.argument_types[0].kind}"
puts "State type: #{aggregate.state_type}"
puts "Initial condition: #{aggregate.initial_state}"
puts "State function: #{aggregate.state_function.name}"
puts "Final function: #{aggregate.final_function.name}"

When

it is executed

Then

its output should contain:

CREATE AGGREGATE simplex.average(int)
  SFUNC avgstate
  STYPE tuple<int, bigint>
  FINALFUNC avgfinal
  INITCOND (0, 0);

Name: average
Return type: double
Argument type: int
State type: tuple<int, bigint>
Initial condition: (0, 0)
State function: avgstate
Final function: avgfinal

since cassadra v3.0

Getting materialized view metadata

Given

the following schema:

CREATE KEYSPACE simplex WITH replication = {'class': 'SimpleStrategy', 'replication_factor': 3};
CREATE TABLE simplex.test_table (f1 int PRIMARY KEY, f2 int, f3 int) ;
CREATE MATERIALIZED VIEW simplex.test_view AS
 SELECT f1, f2 FROM simplex.test_table WHERE f2 IS NOT NULL
 PRIMARY KEY (f1, f2);

And

the following example:

require 'cassandra'

cluster = Cassandra.cluster

mv_meta = cluster.keyspace('simplex').materialized_view('test_view')
puts "Name: #{mv_meta.name}"
puts "Base table: #{mv_meta.base_table.name}"
puts "Keyspace: #{mv_meta.keyspace.name}"
puts "Partition key: #{mv_meta.partition_key[0].name}"
puts "Clustering column: #{mv_meta.clustering_columns[0].name}"
puts "Num columns: #{mv_meta.columns.size}"

puts ""
puts mv_meta.to_cql

When

it is executed

Then

its output should contain:

Name: test_view
Base table: test_table
Keyspace: simplex
Partition key: f1
Clustering column: f2
Num columns: 2

CREATE MATERIALIZED VIEW simplex.test_view AS
SELECT "f1", "f2"
FROM simplex.test_table
WHERE f2 IS NOT NULL
PRIMARY KEY (("f1"), "f2")
WITH bloom_filter_fp_chance = 0.01
 AND caching = {'keys': 'ALL', 'rows_per_partition': 'NONE'}
 AND comment = ''
 AND compaction = {'class': 'SizeTieredCompactionStrategy', 'max_threshold': '32', 'min_threshold': '4'}
 AND compression = {'chunk_length_in_kb': '64', 'class': 'LZ4Compressor'}
 AND crc_check_chance = 1.0
 AND dclocal_read_repair_chance = 0.1
 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 = '99PERCENTILE';

Contents

Schema Metadata

Background

Getting keyspace metadata

Getting table metadata

Getting index metadata

Getting index metadata on full collections

Getting multiple index metadata on same column

Getting user-defined type metadata

Getting user-defined functions and metadata

Getting user-defined aggregates and metadata

Getting materialized view metadata