[GitHub] [arrow] romainfrancois commented on pull request #7807: ARROW-6537 [R]: Pass column_types to CSV reader

[GitBox <gi...@apache.org>]

romainfrancois commented on pull request #7807:
URL: https://github.com/apache/arrow/pull/7807#issuecomment-691148776


   It feels complicated to bend the various options from `ParseOptions`, `ConvertOptions` and `ReadOptions` to something that looks like `readr::` as they mean different things. 
   
   e.g. `ConvertOptions/column_types` which we know handle with a `schema` is only used to specify the types of some columns. 
   
   ```
   /// Optional per-column types (disabling type inference on those columns)
   ```
   
   and then `ReadOptions/column_names` gives the names of all the columns: 
   
   ```
     /// Column names for the target table.
     /// If empty, fall back on autogenerate_column_names.
     std::vector<std::string> column_names;
     /// Whether to autogenerate column names if `column_names` is empty.
     /// If true, column names will be of the form "f0", "f1"...
     /// If false, column names will be read from the first CSV row after `skip_rows`.
     bool autogenerate_column_names = false;
   ```
   
   There is also `ConvertOptions/include_columns` to control which to keep
   
   ```
     /// If non-empty, indicates the names of columns from the CSV file that should
     /// be actually read and converted (in the vector's order).
     /// Columns not in this vector will be ignored.
     std::vector<std::string> include_columns;
   ```
    
   
   


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