left-join loses row

[michaelballantyne]

Hi there! I'm not sure if anybody is still maintaining this, but I seem to have run into a bug.

#lang racket
(require sawzall)
(define df (column-df [handle1 (vector "a" #f "c")]
                      [handle2 (vector "f" "g" "d")]))
(show (left-join (row-df [handle1] "a") df "handle1"))

I expect the program above to produce a result like

┌───────┬───────┐
│handle1│handle2│
├───────┼───────┤
│a      │f      │
└───────┴───────┘

but instead I get an empty dataframe.

It seems as though this only happens when the key I'm using in the query, here the "a", is the smallest key in the df I'm joining on, and when there is a #f value somewhere in the column. That is,

(left-join (row-df [handle1] "c") df "handle1")

and

(left-join (row-df [handle2] "d") df "handle2")

Thanks for the nice library!