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 '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:

$cluster = Dse::cluster()->build();
$session = $cluster->connect("simplex");
$schema = $session->schema();

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

echo "Name => {$function->simpleName()}" . PHP_EOL;
echo "Signature => {$function->signature()}" . PHP_EOL;
echo "Language => {$function->language()}" . PHP_EOL;
echo "Body => {$function->body()}" . PHP_EOL;
echo "Arguments:" . PHP_EOL;
foreach ($function->arguments() as $name => $type) {
    echo "  {$name} => {$type}" . PHP_EOL;
}
echo "Return Type => {$function->returnType()}" . PHP_EOL;
echo "Is Called On Null Input => " . ($function->isCalledOnNullInput() ? "true" : "false") . PHP_EOL;

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:
  input => double
Return Type => double
Is Called On Null Input => true

Getting an aggregates’s metadata

Given

the following example:

$cluster = Dse::cluster()->build();
$session = $cluster->connect("simplex");
$schema = $session->schema();

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

echo "Name => {$aggregate->simpleName()}" . PHP_EOL;
echo "Signature => {$aggregate->signature()}" . PHP_EOL;
echo "Argument Types:" . PHP_EOL;
foreach ($aggregate->argumentTypes() as $index => $type) {
    echo "  {$index} => {$type}" . PHP_EOL;
}
echo "State Type => {$aggregate->stateType()}" . PHP_EOL;
echo "Return Type => {$aggregate->returnType()}" . PHP_EOL;
echo "Initial Condition: {$aggregate->initialCondition()}" . PHP_EOL;
echo "State Function: {$aggregate->stateFunction()->signature()}" . PHP_EOL;
echo "Final Function: {$aggregate->finalFunction()->signature()}" . PHP_EOL;

When

it is executed

Then

its output should contain:

Name => average
Signature => average(int)
Argument Types:
  0 => int
State Type => tuple<int, bigint>
Return Type => double
Initial Condition: (0, 0)
State Function: avgstate(frozen<tuple<int,bigint>>,int)
Final Function: avgfinal(frozen<tuple<int,bigint>>)