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  1. Apache Arrow
  2. ARROW-8867

[R] Support converting POSIXlt type

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    • New Feature
    • Status: Resolved
    • Major
    • Resolution: Fixed
    • None
    • 1.0.0
    • R

    Description

      f <- as.POSIXlt(Sys.time() + 1:5)
      Array$create(f)
      # Error in Array__from_vector(x, type) : 
      #   Unknown: List vector expecting elements vector of type double but got int32
      

      Issue #1: POSIXlt type is a struct, essentially. But because it is not a data.frame, we don't try to convert it to a struct. (We should probably convert named lists to structs and not list type in general.)

      If I trick the converter into thinking it is a data.frame, it will convert to struct successfully.

      class(f) <- c(class(f), "data.frame")
      Array$create(f)
      # StructArray
      # <struct<sec: double, min: int32, hour: int32, mday: int32, mon: int32, year: int32, wday: int32, yday: int32, isdst: int32, zone: string, gmtoff: int32>>
      # ...
      

      Issue #2: round trip won't work because the attributes that tell you that this struct is a POSIXlt type, what time zone it is, etc., are dropped. This would be helped by storing those attributes as custom_metadata on the Table. (We could also implement it as an extension type, but if it's just for going back and forth between R, would that have any benefit?)

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              npr Neal Richardson
              npr Neal Richardson
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