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  1. Apache Arrow
  2. ARROW-6338

[R] Type function names don't match type names

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    Details

    • Type: Improvement
    • Status: Resolved
    • Priority: Major
    • Resolution: Fixed
    • Affects Version/s: None
    • Fix Version/s: 0.15.0
    • Component/s: R

      Description

      I noticed this while working on documentation for ARROW-5505, trying to show how you could pass an explicit schema definition to make a table. For a few types, the name of the type that gets printed (and comes from the C++ library) doesn't match the name of the function you use to specify the type in a schema:

      > tab <- to_arrow(data.frame(
      +   a = 1:10,
      +   b = as.numeric(1:10),
      +   c = sample(c(TRUE, FALSE, NA), 10, replace = TRUE),
      +   d = letters[1:10],
      +   stringsAsFactors = FALSE
      + ))
      > tab$schema
      arrow::Schema 
      a: int32
      b: double
      c: bool
      d: string 
      # Alright, let's make that schema
      > schema(a = int32(), b = double(), c = bool(), d = string())
      Error in bool() : could not find function "bool"
      # Hmm, ok, so bool --> boolean()
      > schema(a = int32(), b = double(), c = boolean(), d = string())
      Error in string() : could not find function "string"
      # string --> utf8()
      > schema(a = int32(), b = double(), c = boolean(), d = utf8())
      Error: type does not inherit from class arrow::DataType
      # Wha?
      > double()
      numeric(0)
      # Oh. double is a base R function.
      > schema(a = int32(), b = float64(), c = boolean(), d = utf8())
      arrow::Schema 
      a: int32
      b: double
      c: bool
      d: string 
      

      If you believe this switch statement is correct, these three, along with float and half_float, are the only mismatches: https://github.com/apache/arrow/blob/master/r/R/R6.R#L81-L109

      > schema(b = float64(), c = boolean(), d = utf8(), e = float32(), f = float16())
      arrow::Schema 
      b: double
      c: bool
      d: string
      e: float
      f: halffloat 
      

      I can add aliases (i.e. another function that does the same thing) for bool, string, float, and halffloat, and I can add some magic so that double() (and even integer()) work inside the schema() function. But in looking into the C++ side to confirm where these alternate type names were coming from, I saw some inconsistencies. For example, https://github.com/apache/arrow/blob/master/cpp/src/arrow/type.h#L773-L788 suggests that the StringType should report its name as "utf8". But the ToString method here https://github.com/apache/arrow/blob/master/cpp/src/arrow/type.cc#L191 has it report as "string". It's unclear why those should report differently.

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              • Assignee:
                npr Neal Richardson
                Reporter:
                npr Neal Richardson
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                  Updated:
                  Resolved:

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