Put some Numba in your SQLite

Fair Warning

This library does unsafe things like pass around function pointer addresses as integers. Use at your own risk.

If you're unfamiliar with why passing function pointers' addresses around as integers might be unsafe, then you shouldn't use this library.

Requirements

Python >=3.5
numba

Installation

python setup.py develop

Examples

Scalar Functions

These are almost the same as decorating a Python function with numba.jit. In the case of sqlite_udf a signature is required.

from slumba import sqlite_udf
from numba import int64


@sqlite_udf(int64(int64))
def add_one(x):
    """Add one to `x` if `x` is not NULL
    """
    if x is not None:
	return x + 1
    return None

Aggregate Functions

These follow the API of the Python standard library's sqlite3.Connection.create_aggregate method. The difference with slumba aggregates is that they require two decorators: numba.jitclass and slumba.sqlite_udaf. Let's define the avg (average) function for floating point numbers.

from numba import int64, float64, jitclass
from slumba import sqlite_udaf


@sqlite_udaf(float64(float64))
@jitclass(dict(total=float64, count=int64))
class Avg:
    def __init__(self):
        self.total = 0.0
        self.count = 0

    def step(self, value):
        if value is not None:
	    self.total += value
	    self.count += 1

    def finalize(self):
	if not self.count:
	    return None
        return self.total / self.count