alamb commented on code in PR #6853:
URL: https://github.com/apache/arrow-rs/pull/6853#discussion_r1874409116
##########
arrow-schema/src/ffi.rs:
##########
@@ -685,66 +686,68 @@ impl TryFrom<&DataType> for FFI_ArrowSchema {
}
}
-fn get_format_string(dtype: &DataType) -> Result<String, ArrowError> {
+fn get_format_string(dtype: &DataType) -> Result<Cow<'static, str>,
ArrowError> {
match dtype {
- DataType::Null => Ok("n".to_string()),
- DataType::Boolean => Ok("b".to_string()),
- DataType::Int8 => Ok("c".to_string()),
- DataType::UInt8 => Ok("C".to_string()),
- DataType::Int16 => Ok("s".to_string()),
- DataType::UInt16 => Ok("S".to_string()),
- DataType::Int32 => Ok("i".to_string()),
- DataType::UInt32 => Ok("I".to_string()),
- DataType::Int64 => Ok("l".to_string()),
- DataType::UInt64 => Ok("L".to_string()),
- DataType::Float16 => Ok("e".to_string()),
- DataType::Float32 => Ok("f".to_string()),
- DataType::Float64 => Ok("g".to_string()),
- DataType::BinaryView => Ok("vz".to_string()),
- DataType::Binary => Ok("z".to_string()),
- DataType::LargeBinary => Ok("Z".to_string()),
- DataType::Utf8View => Ok("vu".to_string()),
- DataType::Utf8 => Ok("u".to_string()),
- DataType::LargeUtf8 => Ok("U".to_string()),
- DataType::FixedSizeBinary(num_bytes) => Ok(format!("w:{num_bytes}")),
- DataType::FixedSizeList(_, num_elems) => Ok(format!("+w:{num_elems}")),
- DataType::Decimal128(precision, scale) =>
Ok(format!("d:{precision},{scale}")),
- DataType::Decimal256(precision, scale) =>
Ok(format!("d:{precision},{scale},256")),
- DataType::Date32 => Ok("tdD".to_string()),
- DataType::Date64 => Ok("tdm".to_string()),
- DataType::Time32(TimeUnit::Second) => Ok("tts".to_string()),
- DataType::Time32(TimeUnit::Millisecond) => Ok("ttm".to_string()),
- DataType::Time64(TimeUnit::Microsecond) => Ok("ttu".to_string()),
- DataType::Time64(TimeUnit::Nanosecond) => Ok("ttn".to_string()),
- DataType::Timestamp(TimeUnit::Second, None) => Ok("tss:".to_string()),
- DataType::Timestamp(TimeUnit::Millisecond, None) =>
Ok("tsm:".to_string()),
- DataType::Timestamp(TimeUnit::Microsecond, None) =>
Ok("tsu:".to_string()),
- DataType::Timestamp(TimeUnit::Nanosecond, None) =>
Ok("tsn:".to_string()),
- DataType::Timestamp(TimeUnit::Second, Some(tz)) =>
Ok(format!("tss:{tz}")),
- DataType::Timestamp(TimeUnit::Millisecond, Some(tz)) =>
Ok(format!("tsm:{tz}")),
- DataType::Timestamp(TimeUnit::Microsecond, Some(tz)) =>
Ok(format!("tsu:{tz}")),
- DataType::Timestamp(TimeUnit::Nanosecond, Some(tz)) =>
Ok(format!("tsn:{tz}")),
- DataType::Duration(TimeUnit::Second) => Ok("tDs".to_string()),
- DataType::Duration(TimeUnit::Millisecond) => Ok("tDm".to_string()),
- DataType::Duration(TimeUnit::Microsecond) => Ok("tDu".to_string()),
- DataType::Duration(TimeUnit::Nanosecond) => Ok("tDn".to_string()),
- DataType::Interval(IntervalUnit::YearMonth) => Ok("tiM".to_string()),
- DataType::Interval(IntervalUnit::DayTime) => Ok("tiD".to_string()),
- DataType::Interval(IntervalUnit::MonthDayNano) =>
Ok("tin".to_string()),
- DataType::List(_) => Ok("+l".to_string()),
- DataType::LargeList(_) => Ok("+L".to_string()),
- DataType::Struct(_) => Ok("+s".to_string()),
- DataType::Map(_, _) => Ok("+m".to_string()),
- DataType::RunEndEncoded(_, _) => Ok("+r".to_string()),
+ DataType::Null => Ok(Cow::Borrowed("n")),
Review Comment:
This syntax is totally fine (and very explicit)
I think you can express the same thing using `into` which is less verbose:
For example
```suggestion
DataType::Null => Ok("n".into()),
```
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