[jira] [Updated] (ARROW-14705) [C++] unify_schemas can't handle int64 + double, affects CSV dataset

["Weston Pace (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/ARROW-14705?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Weston Pace updated ARROW-14705:
--------------------------------
    Labels: query-engine  (was: )

> [C++] unify_schemas can't handle int64 + double, affects CSV dataset
> --------------------------------------------------------------------
>
>                 Key: ARROW-14705
>                 URL: https://issues.apache.org/jira/browse/ARROW-14705
>             Project: Apache Arrow
>          Issue Type: Bug
>          Components: C++, R
>            Reporter: Neal Richardson
>            Priority: Major
>              Labels: query-engine
>
> Twitter question of "how can I make arrow's csv reader not make int64 for integers", turns out to be originating from the scenario where some csvs in a directory may have all integer values for a column but there are decimals in others, and you can't use them together in a dataset.
> {code:r}
> library(arrow, warn.conflicts = FALSE)
> library(dplyr, warn.conflicts = FALSE)
> ds_dir <- tempfile()
> dir.create(ds_dir)
> cat("a\n1", file = file.path(ds_dir, "1.csv"))
> cat("a\n1.1", file = file.path(ds_dir, "2.csv"))
> ds <- open_dataset(ds_dir, format = "csv")
> ds
> #> FileSystemDataset with 2 csv files
> #> a: int64
> ## It just picked the schema of the first file
> collect(ds)
> #> Error: Invalid: Could not open CSV input source '/private/var/folders/yv/b6mwztyj0r11r8pnsbmpltx00000gn/T/RtmpzENOMb/filea9c3292e06dd/2.csv': Invalid: In CSV column #0: Row #2: CSV conversion error to int64: invalid value '1.1'
> #> ../src/arrow/csv/converter.cc:492  decoder_.Decode(data, size, quoted, &value)
> #> ../src/arrow/csv/parser.h:123  status
> #> ../src/arrow/csv/converter.cc:496  parser.VisitColumn(col_index, visit)
> #> ../src/arrow/csv/reader.cc:462  internal::UnwrapOrRaise(maybe_decoded_arrays)
> #> ../src/arrow/compute/exec/exec_plan.cc:398  iterator_.Next()
> #> ../src/arrow/record_batch.cc:318  ReadNext(&batch)
> #> ../src/arrow/record_batch.cc:329  ReadAll(&batches)
> ## Let's try again and tell it to unify schemas. Should result in a float64 type
> ds <- open_dataset(ds_dir, format = "csv", unify_schemas = TRUE)
> #> Error: Invalid: Unable to merge: Field a has incompatible types: int64 vs double
> #> ../src/arrow/type.cc:1621  fields_[i]->MergeWith(field)
> #> ../src/arrow/type.cc:1684  AddField(field)
> #> ../src/arrow/type.cc:1755  builder.AddSchema(schema)
> #> ../src/arrow/dataset/discovery.cc:251  Inspect(options.inspect_options)
> {code}



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