[ENH] improve conditional_join performance

[samukweku]

adapted from here

import numpy as np
import janitor
import pandas as pd
def east_west():
    num_rows_left, num_rows_right = 5_000_000, 5_000_000
    rng = np.random.default_rng(42)

    # Generate two separate datasets where revenue/cost are linearly related to
    # duration/time, but add some noise to the west table so that there are some
    # rows where the cost for the same or greater time will be less than the east table.
    east_dur = rng.integers(1_000, 10_000_000, num_rows_left)
    east_rev = (east_dur * 0.123).astype(np.int32)
    west_time = rng.integers(1_000, 500_000, num_rows_right)
    west_cost = west_time * 0.123
    west_cost += rng.normal(0.0, 1.0, num_rows_right)
    west_cost = west_cost.astype(np.int32)

    east = pd.DataFrame(
        {
            "id": np.arange(0, num_rows_left),
            "dur": east_dur,
            "rev": east_rev,
            "cores": rng.integers(1, 10, num_rows_left),
        }
    )
    west = pd.DataFrame(
        {
            "t_id": np.arange(0, num_rows_right),
            "time": west_time,
            "cost": west_cost,
            "cores": rng.integers(1, 10, num_rows_right),
        }
    )
    return east, west
east,west = east_west()
%timeit eastt.conditional_join(westt, ('dur','time','<='),('rev','cost','>='), ('id','t_id', '>'), use_numba=False)
2.61 s ± 21 ms per loop (mean ± std. dev. of 7 runs, 1 loop each)

%timeit eastt.conditional_join(westt, ('dur','time','<='),('rev','cost','>='), ('id','t_id', '>'), use_numba=True)
11.3 s ± 55.8 ms per loop (mean ± std. dev. of 7 runs, 1 loop each)

speed difference is large. worth looking into