User-defined Function (UDF) and Aggregate Metadata (UDA)

PHP Driver exposes the Cassandra Schema Metadata for UDFs and UDAs.

Background

Given

a running cassandra cluster

And

the following schema:

CREATE KEYSPACE simplex WITH replication = {
  'class': 'SimpleStrategy',
  'replication_factor': 1
} AND DURABLE_WRITES = false;
USE simplex;
CREATE OR REPLACE FUNCTION fLog (input double) CALLED ON NULL INPUT RETURNS double LANGUAGE java AS 'return Double.valueOf(Math.log(input.doubleValue()));';
CREATE OR REPLACE FUNCTION 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 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 AGGREGATE IF NOT EXISTS average ( int ) SFUNC avgState STYPE tuple<int,bigint> FINALFUNC avgFinal INITCOND (0,0);

Getting a function’s metadata

Given

the following example:

<?php
$cluster = Cassandra::cluster()
                  ->withContactPoints('127.0.0.1')
                  ->build();
$session = $cluster->connect("simplex");
$schema = $session->schema();

$function = $schema->keyspace("simplex")->function("flog", Cassandra\Type::double());

echo "Name: " . $function->simpleName() . "\n";
echo "Signature: " . $function->signature() . "\n";
echo "Language: " . $function->language() . "\n";
echo "Body: " . $function->body() . "\n";
echo "Arguments: " . var_export($function->arguments(), true) . "\n";
echo "ReturnType: " . var_export($function->returnType(), true) . "\n";
echo "IsCalledOnNullInput: " . ($function->isCalledOnNullInput() ? "true" : "false") . "\n";

When

it is executed

Then

its output should contain:

Name: flog
Signature: flog(double)
Language: java
Body: return Double.valueOf(Math.log(input.doubleValue()));
Arguments: array (
  'input' =>
  Cassandra\Type\Scalar::__set_state(array(
     'name' => 'double',
  )),
)
ReturnType: Cassandra\Type\Scalar::__set_state(array(
   'name' => 'double',
))
IsCalledOnNullInput: true

Getting an aggregates’s metadata

Given

the following example:

<?php
$cluster = Cassandra::cluster()
                  ->withContactPoints('127.0.0.1')
                  ->build();
$session = $cluster->connect("simplex");
$schema = $session->schema();

$aggregate = $schema->keyspace("simplex")->aggregate("average", Cassandra\Type::int());

echo "Name: " . $aggregate->simpleName() . "\n";
echo "Signature: " . $aggregate->signature() . "\n";
echo "ArgumentTypes: " . var_export($aggregate->argumentTypes(), true) . "\n";
echo "StateType: " . var_export($aggregate->stateType(), true) . "\n";
echo "ReturnType: " . var_export($aggregate->returnType(), true) . "\n";
echo "InitialCondition: " . var_export($aggregate->initialCondition(), true) . "\n";
echo "StateFunction: " .  $aggregate->stateFunction()->signature() . "\n";
echo "FinalFunction: " .  $aggregate->finalFunction()->signature() . "\n";

When

it is executed

Then

its output should contain:

Name: average
Signature: average(int)
ArgumentTypes: array (
  0 =>
  Cassandra\Type\Scalar::__set_state(array(
     'name' => 'int',
  )),
)
StateType: Cassandra\Type\Tuple::__set_state(array(
   'types' =>
  array (
    0 =>
    Cassandra\Type\Scalar::__set_state(array(
       'name' => 'int',
    )),
    1 =>
    Cassandra\Type\Scalar::__set_state(array(
       'name' => 'bigint',
    )),
  ),
))
ReturnType: Cassandra\Type\Scalar::__set_state(array(
   'name' => 'double',
))
InitialCondition: Cassandra\Tuple::__set_state(array(
   'type' =>
  Cassandra\Type\Tuple::__set_state(array(
     'types' =>
    array (
      0 =>
      Cassandra\Type\Scalar::__set_state(array(
         'name' => 'int',
      )),
      1 =>
      Cassandra\Type\Scalar::__set_state(array(
         'name' => 'bigint',
      )),
    ),
  )),
   'values' =>
  array (
    0 => 0,
    1 =>
    Cassandra\Bigint::__set_state(array(
       'type' =>
      Cassandra\Type\Scalar::__set_state(array(
         'name' => 'bigint',
      )),
       'value' => '0',
    )),
  ),
))
StateFunction: avgstate(frozen<tuple<int,bigint>>,int)
FinalFunction: avgfinal(frozen<tuple<int,bigint>>)