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Posted to github@arrow.apache.org by "tustvold (via GitHub)" <gi...@apache.org> on 2023/06/14 11:09:06 UTC
[GitHub] [arrow-rs] tustvold opened a new pull request, #4415: Add DictionaryArray::occupancy
tustvold opened a new pull request, #4415:
URL: https://github.com/apache/arrow-rs/pull/4415
# Which issue does this PR close?
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Part of #4414
Relates to https://github.com/apache/arrow-rs/issues/506
# Rationale for this change
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Split out from #3558 this adds a `DictionaryArray::occupancy` which provides a mask of the "used" values. This is effectively a selection vector for the values (#4095)
# What changes are included in this PR?
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# Are there any user-facing changes?
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[GitHub] [arrow-rs] tustvold merged pull request #4415: Add DictionaryArray::occupancy
Posted by "tustvold (via GitHub)" <gi...@apache.org>.
tustvold merged PR #4415:
URL: https://github.com/apache/arrow-rs/pull/4415
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[GitHub] [arrow-rs] alamb commented on a diff in pull request #4415: Add DictionaryArray::occupancy
Posted by "alamb (via GitHub)" <gi...@apache.org>.
alamb commented on code in PR #4415:
URL: https://github.com/apache/arrow-rs/pull/4415#discussion_r1231344888
##########
arrow-array/src/array/dictionary_array.rs:
##########
@@ -549,6 +550,29 @@ impl<K: ArrowDictionaryKeyType> DictionaryArray<K> {
.for_each(|v| *v = op(*v));
Ok(builder.finish())
}
+
+ /// Computes an occupancy mask for this dictionary's values
+ ///
+ /// For each value in [`Self::values`] the corresponding bit will be set in the
+ /// returned mask if it is referenced by a key in this [`DictionaryArray`]
+ pub fn occupancy(&self) -> BooleanBuffer {
+ let len = self.values.len();
+ let mut builder = BooleanBufferBuilder::new(len);
+ builder.resize(len);
+ let slice = builder.as_slice_mut();
+ match self.keys.nulls().filter(|n| n.null_count() > 0) {
Review Comment:
This is a fancy way to check for nulls -- TIL `Option::filter` 👍
##########
arrow-array/src/array/dictionary_array.rs:
##########
@@ -549,6 +550,29 @@ impl<K: ArrowDictionaryKeyType> DictionaryArray<K> {
.for_each(|v| *v = op(*v));
Ok(builder.finish())
}
+
+ /// Computes an occupancy mask for this dictionary's values
+ ///
+ /// For each value in [`Self::values`] the corresponding bit will be set in the
+ /// returned mask if it is referenced by a key in this [`DictionaryArray`]
+ pub fn occupancy(&self) -> BooleanBuffer {
+ let len = self.values.len();
+ let mut builder = BooleanBufferBuilder::new(len);
+ builder.resize(len);
+ let slice = builder.as_slice_mut();
+ match self.keys.nulls().filter(|n| n.null_count() > 0) {
+ Some(n) => {
+ let v = self.keys.values();
+ n.valid_indices()
+ .for_each(|idx| set_bit(slice, v[idx].as_usize()))
Review Comment:
Would there be any value in calling `valid_slices` here instead? I assume it would be a tradeoff for sparse dictionaries and mostly used dictionaries.
##########
arrow-array/src/array/dictionary_array.rs:
##########
@@ -549,6 +550,29 @@ impl<K: ArrowDictionaryKeyType> DictionaryArray<K> {
.for_each(|v| *v = op(*v));
Ok(builder.finish())
}
+
+ /// Computes an occupancy mask for this dictionary's values
+ ///
+ /// For each value in [`Self::values`] the corresponding bit will be set in the
+ /// returned mask if it is referenced by a key in this [`DictionaryArray`]
+ pub fn occupancy(&self) -> BooleanBuffer {
+ let len = self.values.len();
+ let mut builder = BooleanBufferBuilder::new(len);
+ builder.resize(len);
+ let slice = builder.as_slice_mut();
Review Comment:
nit: calling this `target` or `dest` or `dst` I think would be a more descriptive name for what it is rather than `slice`
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[GitHub] [arrow-rs] alamb commented on pull request #4415: Add DictionaryArray::occupancy
Posted by "alamb (via GitHub)" <gi...@apache.org>.
alamb commented on PR #4415:
URL: https://github.com/apache/arrow-rs/pull/4415#issuecomment-1613680596
is this PR waiting on anything else? Or shall we merge it?
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[GitHub] [arrow-rs] alamb commented on pull request #4415: Add DictionaryArray::occupancy
Posted by "alamb (via GitHub)" <gi...@apache.org>.
alamb commented on PR #4415:
URL: https://github.com/apache/arrow-rs/pull/4415#issuecomment-1593478403
As an aside, I really like how the new ScalarBuffer / NullBuffer structures are so easy to work with ❤️
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