函数

CREATE FUNCTION sample ( arg int ) ...;
CREATE FUNCTION sample ( arg text ) ...;

CREATE FUNCTION some_function ( arg int )
    RETURNS NULL ON NULL INPUT
    RETURNS int
    LANGUAGE java
    AS $$ return arg; $$;

SELECT some_function(column) FROM atable ...;
UPDATE atable SET col = some_function(?) ...;

CREATE TYPE custom_type (txt text, i int);
CREATE FUNCTION fct_using_udt ( udtarg frozen )
    RETURNS NULL ON NULL INPUT
    RETURNS text
    LANGUAGE java
    AS $$ return udtarg.getString("txt"); $$;

CREATE TYPE custom_type (txt text, i int);
CREATE FUNCTION fct\_using\_udt ( somearg int )
    RETURNS NULL ON NULL INPUT
    RETURNS custom_type
    LANGUAGE java
    AS $$
        UDTValue udt = udfContext.newReturnUDTValue();
        udt.setString("txt", "some string");
        udt.setInt("i", 42);
        return udt;
    $$;

public interface UDFContext
{
    UDTValue newArgUDTValue(String argName);
    UDTValue newArgUDTValue(int argNum);
    UDTValue newReturnUDTValue();
    UDTValue newUDTValue(String udtName);
    TupleValue newArgTupleValue(String argName);
    TupleValue newArgTupleValue(int argNum);
    TupleValue newReturnTupleValue();
    TupleValue newTupleValue(String cqlDefinition);
}

import java.nio.ByteBuffer;
import java.util.List;
import java.util.Map;
import java.util.Set;
import org.apache.cassandra.cql3.functions.UDFContext;
import com.datastax.driver.core.TypeCodec;
import com.datastax.driver.core.TupleValue;
import com.datastax.driver.core.UDTValue;

create_function_statement::= CREATE [ OR REPLACE ] FUNCTION [ IF NOT EXISTS]
	function_name '(' arguments_declaration ')'
	[ CALLED | RETURNS NULL ] ON NULL INPUT
	RETURNS cql_type
	LANGUAGE identifier
	AS string arguments_declaration: identifier cql_type ( ',' identifier cql_type )*

CREATE OR REPLACE FUNCTION somefunction(somearg int, anotherarg text, complexarg frozen<someUDT>, listarg list)
    RETURNS NULL ON NULL INPUT
    RETURNS text
    LANGUAGE java
    AS $$
        // some Java code
    $$;

CREATE FUNCTION IF NOT EXISTS akeyspace.fname(someArg int)
    CALLED ON NULL INPUT
    RETURNS text
    LANGUAGE java
    AS $$
        // some Java code
    $$;

drop_function_statement::= DROP FUNCTION [ IF EXISTS ] function_name [ '(' arguments_signature ')' ]
arguments_signature::= cql_type ( ',' cql_type )*

DROP FUNCTION myfunction;
DROP FUNCTION mykeyspace.afunction;
DROP FUNCTION afunction ( int );
DROP FUNCTION afunction ( text );

CREATE OR REPLACE FUNCTION test.averageState(state tuple<int,bigint>, val int)
    CALLED ON NULL INPUT
    RETURNS tuple
    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 test.averageFinal (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 test.average(int)
    SFUNC averageState
    STYPE tuple
    FINALFUNC averageFinal
    INITCOND (0, 0);

CREATE TABLE test.atable (
    pk int PRIMARY KEY,
    val int
);

INSERT INTO test.atable (pk, val) VALUES (1,1);
INSERT INTO test.atable (pk, val) VALUES (2,2);
INSERT INTO test.atable (pk, val) VALUES (3,3);
INSERT INTO test.atable (pk, val) VALUES (4,4);

SELECT test.average(val) FROM atable;

create_aggregate_statement ::= CREATE [ OR REPLACE ] AGGREGATE [ IF NOT EXISTS ]
                                function_name '(' arguments_signature')'
                                SFUNC function_name
                                STYPE cql_type:
                                [ FINALFUNC function_name]
                                [ INITCOND term ]

drop_aggregate_statement::= DROP AGGREGATE [ IF EXISTS ] function_name[ '(' arguments_signature ')'
]

DROP AGGREGATE myAggregate;
DROP AGGREGATE myKeyspace.anAggregate;
DROP AGGREGATE someAggregate ( int );
DROP AGGREGATE someAggregate ( text );