Defining and using external functions

cmath abs

The external keyword provides a way of calling C functions defined in other libraries within Python code.

from test_external_functions of rbc/tests/heavydb/test_howtos.py

from rbc.external import external
cmath_abs = external('int64 abs(int64)')

@heavydb('int64(int64)')
def apply_abs(x):
    return cmath_abs(x)

Example SQL Query

from test_external_functions of rbc/tests/heavydb/test_howtos.py

assert apply_abs(-3).execute() == 3

RBC already exposes a small set of C functions from the C stdlib. Check the API reference page for more details.

Using printf

from test_external_functions of rbc/tests/heavydb/test_howtos.py

from rbc.externals.stdio import printf

@heavydb('int64(int64)')
def power_2(x):
    # This message will show in the heavydb logs
    printf("input number: %d\n", x)
    return x * x

Example SQL Query

from test_external_functions of rbc/tests/heavydb/test_howtos.py

assert power_2(3).execute() == 9