comphead commented on code in PR #26377:
URL: https://github.com/apache/datafusion/pull/26377#discussion_r4285413144
##########
datafusion/functions/src/strings.rs:
##########
@@ -829,38 +832,78 @@ impl StringViewArrayBuilder {
Self::make_long_view_checked(length, buffer_index, offset,
prefix_bytes)
}
- /// See [`BulkNullStringArrayBuilder::append_byte_map`].
+ /// Fallible variant of [`Self::append_byte_map`].
///
/// # Safety
///
/// The bytes produced by applying `map` to each byte of `src`, in order,
/// must form valid UTF-8.
///
- /// # Panics
+ /// # Errors
///
- /// Panics under the same conditions as [`Self::append_value`]: if
- /// `src.len()`, the in-progress buffer offset, or the number of completed
- /// buffers exceeds `i32::MAX`.
+ /// Returns an error under the same conditions as
+ /// [`Self::try_append_value`].
#[inline]
- pub unsafe fn append_byte_map<F: FnMut(u8) -> u8>(&mut self, src: &[u8],
mut map: F) {
- let length: u32 =
- i32::try_from(src.len()).expect("value length exceeds i32::MAX")
as u32;
- if length <= 12 {
- let mut bytes = [0u8; 12];
- for (d, &b) in bytes[..src.len()].iter_mut().zip(src) {
+ pub unsafe fn try_append_byte_map<F: FnMut(u8) -> u8>(
+ &mut self,
+ src: &[u8],
+ mut map: F,
+ ) -> Result<()> {
+ if src.len() <= MAX_INLINE_LEN {
+ // An inline view holds the length in its low 4 bytes, followed by
+ // the value zero-padded to 12 bytes. Writing the mapped bytes
+ // straight into it is faster than going through `inline_view`.
+ let mut view = (src.len() as u128).to_le_bytes();
+ for (d, &b) in view[4..].iter_mut().zip(src) {
*d = map(b);
}
- self.views.push(make_view(&bytes[..src.len()], 0, 0));
- return;
+ self.views.push(u128::from_le_bytes(view));
+ return Ok(());
}
- self.ensure_long_capacity(length);
+ let length: u32 = i32::try_from(src.len())
+ .map_err(|_| string_view_overflow_error("value length"))?
+ as u32;
+ self.try_ensure_long_capacity(length)?;
let cursor = self.in_progress.len();
- let offset: u32 = i32::try_from(cursor).expect("offset exceeds
i32::MAX") as u32;
+ let offset: u32 = i32::try_from(cursor)
+ .map_err(|_| string_view_overflow_error("offset"))?
+ as u32;
+ let buffer_index: u32 = i32::try_from(self.completed.len())
+ .map_err(|_| string_view_overflow_error("buffer count"))?
+ as u32;
self.in_progress.extend(src.iter().map(|&b| map(b)));
Review Comment:
The PR's own table points the same way. `translate` on `Utf8View` is flat at
len 1024 (937.7 µs → 940.8 µs, +0.3%) while `Utf8` improves 25%. `translate`
reaches this long-value branch through `append_byte_map`, so that case should
show the effect of copy-then-map.
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