尝试连接具有 integer64 值列作为主键的表时出现意外错误。下面说明问题——
Keys as int
-----------
x <- data.table(c1=c(1,2,3), c3=c(10,20,30))
z <- data.table(c1=c(1,2), c2=c(100,200))
setkey(x, c1)
setkey(z, c1)
> z[x] # Join works fine
c1 c2 c3
1: 1 100 10
2: 2 200 20
3: 3 NA 30
As integer64
------------
library(bit64)
x[,c1:=as.integer64(c1)]
z[,c1:=as.integer64(c1)]
setkey(x, c1)
setkey(z, c1)
> z[x] # Same join, but generates error message
Error in vecseq(f__, len__, if (allow.cartesian) NULL else as.integer(max(nrow(x), :
Join results in 6 rows; more than 3 = max(nrow(x),nrow(i)). Check for duplicate key values
in i, each of which join to the same group in x over and over again. If that's ok, try
including `j` and dropping `by` (by-without-by) so that j runs for each group to avoid the
large allocation. If you are sure you wish to proceed, rerun with allow.cartesian=TRUE.
Otherwise, please search for this error message in the FAQ, Wiki, Stack Overflow and
datatable-help for advice.
关于问题可能是什么的任何想法？我在更大的桌子上遇到同样的错误。作为一种解决方法，我不得不将 integer64 值转换为字符，之后它可以正常工作。
> sessionInfo()
R version 3.0.1 (2013-05-16)
Platform: x86_64-apple-darwin10.8.0 (64-bit)
...
other attached packages:
[1] bit64_0.9-2 bit_1.1-10 cluster_1.14.4 skmeans_0.2-4 ggplot2_0.9.3.1
[6] data.table_1.8.11
提前致谢。