[jira] [Created] (ARROW-14184) [C++] allow joins where the keys include new columns on the left

["Jonathan Keane (Jira)" <ji...@apache.org>]

Jonathan Keane created ARROW-14184:
--------------------------------------

             Summary: [C++] allow joins where the keys include new columns on the left
                 Key: ARROW-14184
                 URL: https://issues.apache.org/jira/browse/ARROW-14184
             Project: Apache Arrow
          Issue Type: Bug
          Components: C++
            Reporter: Jonathan Keane


If I try to join where the key column on the left is new (a rename, or made by an expression) I get an error:

{code}
``` r
library(arrow, warn.conflicts = FALSE)
library(dplyr, warn.conflicts = FALSE)

right_df <- data.frame(
  gear = as.double(c(3:5)),
  col_a = "a"
)

Table$create(mtcars) %>% 
  rename(the_gear = gear) %>%
  left_join(
    right_df,
    by = c(the_gear = "gear")
  ) %>%
  collect()
#> Error: Invalid: No match or multiple matches for key field reference FieldRef.Name(the_gear) on left side of the join
{code}

Interestingly, if the column is renamed/created on the right side, it works just fine:
{code}
Table$create(mtcars) %>% 
  left_join(
    right_df %>% 
      rename(the_gear = gear),
    by = c(gear = "the_gear")
  ) %>%
  collect()
#>     mpg cyl  disp  hp drat    wt  qsec vs am gear carb col_a
#> 1  21.0   6 160.0 110 3.90 2.620 16.46  0  1    4    4     a
#> 2  21.0   6 160.0 110 3.90 2.875 17.02  0  1    4    4     a
#> 3  22.8   4 108.0  93 3.85 2.320 18.61  1  1    4    1     a
#> 4  21.4   6 258.0 110 3.08 3.215 19.44  1  0    3    1     a
#> 5  18.7   8 360.0 175 3.15 3.440 17.02  0  0    3    2     a
#> 6  18.1   6 225.0 105 2.76 3.460 20.22  1  0    3    1     a
#> 7  14.3   8 360.0 245 3.21 3.570 15.84  0  0    3    4     a
#> 8  24.4   4 146.7  62 3.69 3.190 20.00  1  0    4    2     a
#> 9  22.8   4 140.8  95 3.92 3.150 22.90  1  0    4    2     a
#> 10 19.2   6 167.6 123 3.92 3.440 18.30  1  0    4    4     a
#> 11 17.8   6 167.6 123 3.92 3.440 18.90  1  0    4    4     a
#> 12 16.4   8 275.8 180 3.07 4.070 17.40  0  0    3    3     a
#> 13 17.3   8 275.8 180 3.07 3.730 17.60  0  0    3    3     a
#> 14 15.2   8 275.8 180 3.07 3.780 18.00  0  0    3    3     a
#> 15 10.4   8 472.0 205 2.93 5.250 17.98  0  0    3    4     a
#> 16 10.4   8 460.0 215 3.00 5.424 17.82  0  0    3    4     a
#> 17 14.7   8 440.0 230 3.23 5.345 17.42  0  0    3    4     a
#> 18 32.4   4  78.7  66 4.08 2.200 19.47  1  1    4    1     a
#> 19 30.4   4  75.7  52 4.93 1.615 18.52  1  1    4    2     a
#> 20 33.9   4  71.1  65 4.22 1.835 19.90  1  1    4    1     a
#> 21 21.5   4 120.1  97 3.70 2.465 20.01  1  0    3    1     a
#> 22 15.5   8 318.0 150 2.76 3.520 16.87  0  0    3    2     a
#> 23 15.2   8 304.0 150 3.15 3.435 17.30  0  0    3    2     a
#> 24 13.3   8 350.0 245 3.73 3.840 15.41  0  0    3    4     a
#> 25 19.2   8 400.0 175 3.08 3.845 17.05  0  0    3    2     a
#> 26 27.3   4  79.0  66 4.08 1.935 18.90  1  1    4    1     a
#> 27 26.0   4 120.3  91 4.43 2.140 16.70  0  1    5    2     a
#> 28 30.4   4  95.1 113 3.77 1.513 16.90  1  1    5    2     a
#> 29 15.8   8 351.0 264 4.22 3.170 14.50  0  1    5    4     a
#> 30 19.7   6 145.0 175 3.62 2.770 15.50  0  1    5    6     a
#> 31 15.0   8 301.0 335 3.54 3.570 14.60  0  1    5    8     a
#> 32 21.4   4 121.0 109 4.11 2.780 18.60  1  1    4    2     a
{code}



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