chenkovsky commented on code in PR #15924:
URL: https://github.com/apache/datafusion/pull/15924#discussion_r2076561244
##########
datafusion/common/src/scalar/mod.rs:
##########
@@ -3415,6 +3415,100 @@ impl ScalarValue {
.map(|sv| sv.size() - size_of_val(sv))
.sum::<usize>()
}
+
+ /// Compacts the allocation referenced by `self` to the minimum, copying
the data if
+ /// necessary.
+ ///
+ /// This can be relevant when `self` is a list or contains a list as a
nested value, as
+ /// a single list holds an Arc to its entire original array buffer.
+ pub fn compact(&mut self) {
+ match self {
+ ScalarValue::Null
+ | ScalarValue::Boolean(_)
+ | ScalarValue::Float16(_)
+ | ScalarValue::Float32(_)
+ | ScalarValue::Float64(_)
+ | ScalarValue::Decimal128(_, _, _)
+ | ScalarValue::Decimal256(_, _, _)
+ | ScalarValue::Int8(_)
+ | ScalarValue::Int16(_)
+ | ScalarValue::Int32(_)
+ | ScalarValue::Int64(_)
+ | ScalarValue::UInt8(_)
+ | ScalarValue::UInt16(_)
+ | ScalarValue::UInt32(_)
+ | ScalarValue::UInt64(_)
+ | ScalarValue::Date32(_)
+ | ScalarValue::Date64(_)
+ | ScalarValue::Time32Second(_)
+ | ScalarValue::Time32Millisecond(_)
+ | ScalarValue::Time64Microsecond(_)
+ | ScalarValue::Time64Nanosecond(_)
+ | ScalarValue::IntervalYearMonth(_)
+ | ScalarValue::IntervalDayTime(_)
+ | ScalarValue::IntervalMonthDayNano(_)
+ | ScalarValue::DurationSecond(_)
+ | ScalarValue::DurationMillisecond(_)
+ | ScalarValue::DurationMicrosecond(_)
+ | ScalarValue::DurationNanosecond(_)
+ | ScalarValue::Utf8(_)
+ | ScalarValue::LargeUtf8(_)
+ | ScalarValue::Utf8View(_)
+ | ScalarValue::TimestampSecond(_, _)
+ | ScalarValue::TimestampMillisecond(_, _)
+ | ScalarValue::TimestampMicrosecond(_, _)
+ | ScalarValue::TimestampNanosecond(_, _)
+ | ScalarValue::Binary(_)
+ | ScalarValue::FixedSizeBinary(_, _)
+ | ScalarValue::LargeBinary(_)
+ | ScalarValue::BinaryView(_) => (),
+ ScalarValue::FixedSizeList(arr) => {
+ let taken = arrow::compute::take(
+ arr.as_ref(),
+ &Int32Array::from_iter_values([0]),
+ None,
+ )
+ .unwrap();
+ *Arc::make_mut(arr) =
cast::as_fixed_size_list_array(&taken).clone();
Review Comment:
@alamb
in take's comments
```
Note that this kernel, similar to other kernels in this crate,
will avoid allocating where not necessary. Consequently
the returned array may share buffers with the inputs
```
If a large buffer is shared, it's still a problem.
so I didnt choose this method.
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