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https://issues.apache.org/jira/browse/ARROW-17373?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17583184#comment-17583184
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Adam Black edited comment on ARROW-17373 at 8/22/22 8:28 PM:
-------------------------------------------------------------
Here is another reprex. I think this only happens when the write location is
the same as the current location of the open dataset. In the example above
`writePath` and `savePath` are equal.
{{df <- data.frame(x = replicate(1,sample(0:1, 100e6, rep=TRUE)))}}
{{savePath <- file.path(tempdir(), 'arrowTest')}}
{{{}if (!dir.exists(savePath)){}}}{ dir.create(savePath) }
{{arrow::write_feather(df, file.path(savePath, 'part-0.feather'))}}
{{# writing a dataset to a new directory ('arrowTest2') works fine}}
{{writePath <- file.path(tempdir(), 'arrowTest2')}}
if (!dir.exists(writePath)) \{ dir.create(writePath) }
{{dataset <- arrow::open_dataset(savePath, format='feather')}}
{{nrow(dataset)}}
{{#> [1] 100000000}}
{{arrow::write_dataset(dataset = dataset, path = writePath, format =
'feather')}}
{{dataset2 <- arrow::open_dataset(writePath, format='feather')}}
{{nrow(dataset2)}}
{{#> [1] 100000000}}
{{# trying to write an open dataset to it's own path gives an error}}
{{arrow::write_dataset(dataset = dataset2, path = writePath, format =
'feather')}}
{{{}#> Error: Invalid: Expected to read 144 metadata bytes but got 0{}}}{{{}#
and it modifies the dataset{}}}
{{nrow(dataset2)}}
{{#> [1] 1966080}}
{{# But with a smaller dataset there seems to be no issue }}
{{arrow::write_dataset(dataset = head(dataset, 1000), path = savePath, format =
'feather')}}
{{dataset3 <- arrow::open_dataset(savePath, format='feather')}}
{{nrow(dataset3)}}
{{#> [1] 1000}}
was (Author: JIRAUSER289460):
Here is another reprex. I think this only happens when the write location is
the same as the current location of the open dataset. In the example above
`writePath` and `savePath` are equal.
{{df <- data.frame(x = replicate(1,sample(0:1, 100e6, rep=TRUE)))}}
{{savePath <- file.path(tempdir(), 'arrowTest')}}
{{{}if (!dir.exists(savePath)){}}}{ dir.create(savePath) }
{{arrow::write_feather(df, file.path(savePath, 'part-0.feather'))}}
{{# writing a dataset to a new directory ('arrowTest2') works fine}}
{{writePath <- file.path(tempdir(), 'arrowTest2')}}
if (!dir.exists(writePath)) \{ dir.create(writePath) }
{{dataset <- arrow::open_dataset(savePath, format='feather')}}
{{nrow(dataset)}}
{{#> [1] 100000000}}
{{arrow::write_dataset(dataset = dataset, path = writePath, format =
'feather')}}
{{dataset2 <- arrow::open_dataset(writePath, format='feather')}}
{{nrow(dataset2)}}
{{#> [1] 100000000}}
{{trying to write an open dataset to it's own path gives an error}}
{{arrow::write_dataset(dataset = dataset2, path = writePath, format =
'feather')}}
{{{}#> Error: Invalid: Expected to read 144 metadata bytes but got 0{}}}{{{}#
and it modifies the dataset{}}}
{{nrow(dataset2)}}
{{#> [1] 1966080}}
{{# But with a smaller dataset there seems to be no issue }}
{{arrow::write_dataset(dataset = head(dataset, 1000), path = savePath, format =
'feather')}}
{{dataset3 <- arrow::open_dataset(savePath, format='feather')}}
{{nrow(dataset3)}}
{{#> [1] 1000}}
> [R] copying dataset and immediatly writing the copy to a different location
> fails
> ---------------------------------------------------------------------------------
>
> Key: ARROW-17373
> URL: https://issues.apache.org/jira/browse/ARROW-17373
> Project: Apache Arrow
> Issue Type: Bug
> Components: R
> Affects Versions: 9.0.0
> Environment: Ubuntu 22.04
> Reporter: Egill Axfjord Fridgeirsson
> Priority: Major
>
> When I copy large feather files, open a dataset from that file and
> immediately write that dataset to a new location I get the following error:
>
> ```Error: Invalid: Expected to read 144 metadata bytes but got 0```
>
> I have made a reproducible example below:
>
> ``` r
> df <- data.frame(replicate(1,sample(0:1,100e6,rep=TRUE)))
> savePath <- file.path(tempdir(), 'arrowTest')
> if (!dir.exists(savePath)) {
> dir.create(savePath)
> }
> arrow::write_feather(df, file.path(savePath, 'part-0.feather'))
> copyPath <- file.path(tempdir(),'arrowTest')
> if (!dir.exists(copyPath)) {
> dir.create(copyPath)
> }
> writePath <- file.path(tempdir(), 'arrowTest')
> if (!dir.exists(writePath)) {
> dir.create(writePath)
> }
> arrow::copy_files(savePath, copyPath)
> dataset <- arrow::open_dataset(copyPath, format='feather')
> arrow::write_dataset(dataset = dataset, path = writePath, format = 'feather')
> ```
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