[jira] [Commented] (ARROW-6338) [R] Type function names don't match type names

["Francois Saint-Jacques (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ARROW-6338?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16914484#comment-16914484 ] 

Francois Saint-Jacques commented on ARROW-6338:
-----------------------------------------------

The names you want to follow are the factory functions:

* https://github.com/apache/arrow/blob/master/cpp/src/arrow/type_fwd.h#L208-L245
* https://github.com/apache/arrow/blob/master/cpp/src/arrow/type.h#L1358-L1509

As for inconsistencies between ToString(), type_name(), name(), I think it's worth reconciling, [~pitrou].

> [R] Type function names don't match type names
> ----------------------------------------------
>
>                 Key: ARROW-6338
>                 URL: https://issues.apache.org/jira/browse/ARROW-6338
>             Project: Apache Arrow
>          Issue Type: Improvement
>          Components: R
>            Reporter: Neal Richardson
>            Assignee: Neal Richardson
>            Priority: Major
>             Fix For: 0.15.0
>
>
> 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:
> {code:r}
> > 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 
> {code}
> 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]
> {code:r}
> > schema(b = float64(), c = boolean(), d = utf8(), e = float32(), f = float16())
> arrow::Schema 
> b: double
> c: bool
> d: string
> e: float
> f: halffloat 
> {code}
> 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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