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https://issues.apache.org/jira/browse/ARROW-10088?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17202225#comment-17202225
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Neal Richardson commented on ARROW-10088:
-----------------------------------------
My guess is that the issue is related to the fact that you don't have a true
{{integer64}}: the "class" attribute has {{np.ulong}} in there too, so the code
that looks to preserve R attributes is coming in after the downcast and adding
those classes back on.
On the latest development version, there are some changes in the logic, and
this now seems to come out as just "integer". Perhaps try installing a nightly
version of the package and see if you see the same?
Even so, this probably isn't ideal. Maybe you want to be able to control
whether int64 downcasts to R integer (currently it only does it if all values
fit in the int32 range). Maybe you want an explicit "integer64" class from R in
the metadata to mean that you don't downcast, for R roundtrip fidelity. Or
other possibilities. Unclear though that they justify the added complexity, but
happy to discuss.
> [R] Integer64 incorrectly read into R data.table
> ------------------------------------------------
>
> Key: ARROW-10088
> URL: https://issues.apache.org/jira/browse/ARROW-10088
> Project: Apache Arrow
> Issue Type: Bug
> Components: R
> Affects Versions: 1.0.1
> Reporter: Kyle Kavanagh
> Priority: Major
>
> I've got a proprietary dataset where one of the columns is an integer64 but
> all of the values would fit within 32bits. As I understand it, arrow/feather
> will downcast that column when the data is read back into R (not ideal IMO,
> but not an issue generally). However, I'm having some trouble with a
> specific dataset.
> When I read in the data, the column is set to the class "integer64", however
> the column type (typeof) is 'integer' and not 'double', which is the
> underlying type used by bit64. This mismatch causes R data.table to error
> out
> ([https://github.com/Rdatatable/data.table/blob/master/src/rbindlist.c#L325)]
> I do not have any issue with integer64 columns which have values > 2^32, and
> suspiciously I am also unable to recreate the issue by manually creating a
> data.table with an int64 column with small values (e.g
> data.table(col=as.integer64(c(1,2,3))) )
> I did look thru the arrow::r cpp source and couldnt find an obvious case
> where the underlying storage array would be an integer but also have the
> 'integer64' class attr assigned... A fix would either be to remove the
> integer64 class attr, or ensure that the underlying data store is a REALSXP
> instead of INTEGERSXP
> My company's network policies wont let me upload the sample dataset, hoping
> to see if this triggers an immediate thoughts. If not, I can try to figure
> our how to upload the dataset or otherwise provide details from it as
> requested.
>
> {code:java}
> > arrow::write_feather(df[,list(testCol)][1], '~/test.feather')
> > test = arrow::read_feather('~/test.feather')
> > class(test$testCol)
> [1] "integer64" "np.ulong"
> > typeof(test$testCol)
> [1] "integer"
> > str(test)
> Classes ‘tbl_df’, ‘tbl’ and 'data.frame': 1 obs. of 1 variable: $
> testCol:Error in as.character.integer64(object) : REAL() can only be applied
> to a 'numeric', not a 'integer'
> #In the larger original dataset, it handles most columns properly, only the
> 'testCol' breaks things. Note the difference:
> > typeof(df$goodCol)
> [1] "double"
> > class(df$goodCol)
> [1] "integer64" "np.ulong"
> > typeof(df$testCol)
> [1] "integer"
> > class(df$testCol)
> [1] "integer64" "np.ulong"
> > str(df)
> Classes ‘data.table’ and 'data.frame': 214781 obs. of 17 variables:
> $ goodCol :integer64 1599777000000604025 ...
> $ testCol :Error in as.character.integer64(object) :
> > sessionInfo()
> R version 3.6.1 (2019-07-05)Platform: x86_64-pc-linux-gnu (64-bit)Running
> under: Red Hat Enterprise Linux Server 7.7 (Maipo)
> Matrix products: defaultBLAS: /usr/lib64/libblas.so.3.4.2LAPACK:
> /usr/lib64/liblapack.so.3.4.2locale:
> [1] LC_CTYPE=en_US.UTF-8 LC_NUMERIC=C [3] LC_TIME=en_US.UTF-8
> LC_COLLATE=en_US.UTF-8 [5] LC_MONETARY=en_US.UTF-8 LC_MESSAGES=en_US.UTF-8
> [7] LC_PAPER=en_US.UTF-8 LC_NAME=C [9] LC_ADDRESS=C
> LC_TELEPHONE=C[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C
> attached base packages:[1] stats graphics grDevices utils datasets
> methods baseother attached packages:[1] data.table_1.13.0 bit64_4.0.5
> bit_4.0.4loaded via a namespace (and not attached): [1] Rcpp_1.0.5
> lattice_0.20-41 arrow_1.0.1 [4] assertthat_0.2.1 rappdirs_0.3.1
> grid_3.6.1 [7] R6_2.4.1 jsonlite_1.7.1 magrittr_1.5[10]
> rlang_0.4.7 Matrix_1.2-18 vctrs_0.3.4[13]
> reticulate_1.14-9001 tools_3.6.1 glue_1.4.2[16] purrr_0.3.4
> compiler_3.6.1 tidyselect_1.1.0{code}
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