sweb commented on a change in pull request #9047:
URL: https://github.com/apache/arrow/pull/9047#discussion_r550975265
##########
File path: rust/parquet/src/arrow/schema.rs
##########
@@ -591,6 +591,7 @@ impl ParquetTypeConverter<'_> {
LogicalType::INT_32 => Ok(DataType::Int32),
LogicalType::DATE => Ok(DataType::Date32(DateUnit::Day)),
LogicalType::TIME_MILLIS =>
Ok(DataType::Time32(TimeUnit::Millisecond)),
+ LogicalType::DECIMAL => self.to_decimal(),
Review comment:
The cast is necessary, because downcasting an i32 array to i64 results
in None, panicking as a result. I have removed the cast and handle the building
of the decimal array now separately, but I do not really like my solution:
```
let mut builder = DecimalBuilder::new(array.len(), *p, *s);
match array.data_type() {
ArrowType::Int32 => {
let values =
array.as_any().downcast_ref::<Int32Array>().unwrap();
for maybe_value in values.iter() {
match maybe_value {
Some(value) => builder.append_value(value as
i128)?,
None => builder.append_null()?,
}
}
}
ArrowType::Int64 => {
let values =
array.as_any().downcast_ref::<Int64Array>().unwrap();
for maybe_value in values.iter() {
match maybe_value {
Some(value) => builder.append_value(value as
i128)?,
None => builder.append_null()?,
}
}
}
_ => {
return Err(ArrowError(format!(
"Cannot convert {:?} to decimal",
array.data_type()
)))
}
}
```
At the moment, I am not able to convince the compiler to treat downcasts to
i32 and i64 as the same primitive array and then use `as` on the resulting
iterator to convert from types that are unknown at compile time to `i128`. I
will probably need to spend some time figuring this out.
Alternatively, we could use converters, similar to the fixed length case.
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