risingwave 0.0.9

RisingWave Python API

RisingWave Python API

This library provides a Python API for creating user-defined functions (UDF) in RisingWave.

Introduction

RisingWave supports user-defined functions implemented as external functions. With the RisingWave Python UDF SDK, users can define custom UDFs using Python and start a Python process as a UDF server. RisingWave can then remotely access the UDF server to execute the defined functions.

Installation

pip install risingwave

Usage

Define functions in a Python file:

# udf.py
from risingwave.udf import udf, udtf, UdfServer
import struct
import socket

# Define a scalar function
@udf(input_types=['INT', 'INT'], result_type='INT')
def gcd(x, y):
    while y != 0:
        (x, y) = (y, x % y)
    return x

# Define a scalar function that returns multiple values (within a struct)
@udf(input_types=['BYTEA'], result_type='STRUCT<VARCHAR, VARCHAR, SMALLINT, SMALLINT>')
def extract_tcp_info(tcp_packet: bytes):
    src_addr, dst_addr = struct.unpack('!4s4s', tcp_packet[12:20])
    src_port, dst_port = struct.unpack('!HH', tcp_packet[20:24])
    src_addr = socket.inet_ntoa(src_addr)
    dst_addr = socket.inet_ntoa(dst_addr)
    return src_addr, dst_addr, src_port, dst_port

# Define a table function
@udtf(input_types='INT', result_types='INT')
def series(n):
    for i in range(n):
        yield i

# Start a UDF server
if __name__ == '__main__':
    server = UdfServer(location="0.0.0.0:8815")
    server.add_function(gcd)
    server.add_function(series)
    server.serve()

Start the UDF server:

python3 udf.py

To create functions in RisingWave, use the following syntax:

create function <name> ( <arg_type>[, ...] )
    [ returns <ret_type> | returns table ( <column_name> <column_type> [, ...] ) ]
    as <name_defined_in_server> using link '<udf_server_address>';

• The as parameter specifies the function name defined in the UDF server.
• The link parameter specifies the address of the UDF server.

For example:

create function gcd(int, int) returns int
as gcd using link 'http://localhost:8815';

create function series(int) returns table (x int)
as series using link 'http://localhost:8815';

select gcd(25, 15);

select * from series(10);

Data Types

The RisingWave Python UDF SDK supports the following data types:

SQL Type	Python Type	Notes
BOOLEAN	bool
SMALLINT	int
INT	int
BIGINT	int
REAL	float
DOUBLE PRECISION	float
DECIMAL	decimal.Decimal
DATE	datetime.date
TIME	datetime.time
TIMESTAMP	datetime.datetime
INTERVAL	MonthDayNano / (int, int, int)	Fields can be obtained by months(), days() and nanoseconds() from MonthDayNano
VARCHAR	str
BYTEA	bytes
JSONB	any
T[]	list[T]
STRUCT<>	tuple
...others		Not supported yet.