tustvold commented on a change in pull request #1248:
URL: https://github.com/apache/arrow-rs/pull/1248#discussion_r798949820
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File path: arrow/src/compute/kernels/filter.rs
##########
@@ -185,79 +279,559 @@ pub fn prep_null_mask_filter(filter: &BooleanArray) ->
BooleanArray {
/// # Ok(())
/// # }
/// ```
-pub fn filter(array: &dyn Array, predicate: &BooleanArray) -> Result<ArrayRef>
{
- if predicate.null_count() > 0 {
- // this greatly simplifies subsequent filtering code
- // now we only have a boolean mask to deal with
- let predicate = prep_null_mask_filter(predicate);
- return filter(array, &predicate);
+pub fn filter(values: &dyn Array, predicate: &BooleanArray) ->
Result<ArrayRef> {
+ let predicate = FilterBuilder::new(predicate).build();
+ filter_array(values, &predicate)
+}
+
+/// Returns a new [RecordBatch] with arrays containing only values matching
the filter.
+pub fn filter_record_batch(
+ record_batch: &RecordBatch,
+ predicate: &BooleanArray,
+) -> Result<RecordBatch> {
+ let filter = FilterBuilder::new(predicate).optimize().build();
+
+ let filtered_arrays = record_batch
+ .columns()
+ .iter()
+ .map(|a| filter_array(a, &filter))
+ .collect::<Result<Vec<_>>>()?;
+
+ RecordBatch::try_new(record_batch.schema(), filtered_arrays)
+}
+
+/// A builder to construct [`FilterPredicate`]
+#[derive(Debug)]
+pub struct FilterBuilder {
+ filter: BooleanArray,
+ count: usize,
+ iterator: FilterIterator,
+}
+
+impl FilterBuilder {
+ /// Create a new [`FilterBuilder`] that can be used to construct a
[`FilterPredicate`]
+ pub fn new(filter: &BooleanArray) -> Self {
+ let filter = match filter.null_count() {
+ 0 => BooleanArray::from(filter.data().clone()),
+ _ => prep_null_mask_filter(filter),
+ };
+
+ let count = filter_count(&filter);
+ let selectivity_frac = count as f64 / filter.len() as f64;
+ let iterator = if selectivity_frac > 0.8 {
+ FilterIterator::SlicesIterator
+ } else {
+ FilterIterator::IndexIterator
+ };
+
+ Self {
+ filter,
+ count,
+ iterator,
+ }
+ }
+
+ /// Compute an optimised representation of the provided `filter` mask that
can be
+ /// applied to an array more quickly.
+ ///
+ /// Note: There is limited benefit to calling this to then filter a single
array
+ /// Note: This will likely have a larger memory footprint than the
original mask
+ pub fn optimize(mut self) -> Self {
+ match self.iterator {
+ FilterIterator::SlicesIterator => {
+ let slices = SlicesIterator::new(&self.filter).collect();
+ self.iterator = FilterIterator::Slices(slices)
+ }
+ FilterIterator::IndexIterator => {
+ let indices = IndexIterator::new(&self.filter,
self.count).collect();
+ self.iterator = FilterIterator::Indices(indices)
+ }
+ _ => {}
+ }
+ self
+ }
+
+ /// Construct the final `FilterPredicate`
+ pub fn build(self) -> FilterPredicate {
+ FilterPredicate {
+ filter: self.filter,
+ count: self.count,
+ iterator: self.iterator,
+ }
}
+}
- let filter_count = filter_count(predicate);
+/// The internal iterator type of [`FilterPredicate`]
+#[derive(Debug)]
+enum FilterIterator {
+ // A lazily evaluated iterator of ranges
+ SlicesIterator,
+ // A lazily evaluated iterator of indices
+ IndexIterator,
+ // A precomputed list of indices
+ Indices(Vec<usize>),
+ // A precomputed array of ranges
+ Slices(Vec<(usize, usize)>),
+}
+
+/// A filtering predicate that can be applied to an [`Array`]
+#[derive(Debug)]
+pub struct FilterPredicate {
+ filter: BooleanArray,
+ count: usize,
+ iterator: FilterIterator,
+}
- match filter_count {
+impl FilterPredicate {
+ /// Selects rows from `values` based on this [`FilterPredicate`]
+ pub fn filter(&self, values: &dyn Array) -> Result<ArrayRef> {
+ filter_array(values, self)
+ }
+}
+
+fn filter_array(values: &dyn Array, predicate: &FilterPredicate) ->
Result<ArrayRef> {
+ if predicate.filter.len() > values.len() {
+ return Err(ArrowError::InvalidArgumentError(format!(
+ "Filter predicate of length {} is larger than target array of
length {}",
+ predicate.filter.len(),
+ values.len()
+ )));
+ }
+
+ match predicate.count {
0 => {
// return empty
- Ok(new_empty_array(array.data_type()))
+ Ok(new_empty_array(values.data_type()))
}
- len if len == array.len() => {
+ len if len == values.len() => {
// return all
- let data = array.data().clone();
+ let data = values.data().clone();
Ok(make_array(data))
}
- _ => {
- // actually filter
- let mut mutable =
- MutableArrayData::new(vec![array.data_ref()], false,
filter_count);
+ // actually filter
+ _ => match values.data_type() {
+ DataType::Boolean => {
+ let values =
values.as_any().downcast_ref::<BooleanArray>().unwrap();
+ Ok(Arc::new(filter_boolean(values, predicate)))
+ }
+ DataType::Int8 => {
+ downcast_filter!(Int8Type, values, predicate)
+ }
+ DataType::Int16 => {
+ downcast_filter!(Int16Type, values, predicate)
+ }
+ DataType::Int32 => {
+ downcast_filter!(Int32Type, values, predicate)
+ }
+ DataType::Int64 => {
+ downcast_filter!(Int64Type, values, predicate)
+ }
+ DataType::UInt8 => {
+ downcast_filter!(UInt8Type, values, predicate)
+ }
+ DataType::UInt16 => {
+ downcast_filter!(UInt16Type, values, predicate)
+ }
+ DataType::UInt32 => {
+ downcast_filter!(UInt32Type, values, predicate)
+ }
+ DataType::UInt64 => {
+ downcast_filter!(UInt64Type, values, predicate)
+ }
+ DataType::Float32 => {
+ downcast_filter!(Float32Type, values, predicate)
+ }
+ DataType::Float64 => {
+ downcast_filter!(Float64Type, values, predicate)
+ }
+ DataType::Date32 => {
+ downcast_filter!(Date32Type, values, predicate)
+ }
+ DataType::Date64 => {
+ downcast_filter!(Date64Type, values, predicate)
+ }
+ DataType::Time32(Second) => {
+ downcast_filter!(Time32SecondType, values, predicate)
+ }
+ DataType::Time32(Millisecond) => {
+ downcast_filter!(Time32MillisecondType, values, predicate)
+ }
+ DataType::Time64(Microsecond) => {
+ downcast_filter!(Time64MicrosecondType, values, predicate)
+ }
+ DataType::Time64(Nanosecond) => {
+ downcast_filter!(Time64NanosecondType, values, predicate)
+ }
+ DataType::Timestamp(Second, _) => {
+ downcast_filter!(TimestampSecondType, values, predicate)
+ }
+ DataType::Timestamp(Millisecond, _) => {
+ downcast_filter!(TimestampMillisecondType, values, predicate)
+ }
+ DataType::Timestamp(Microsecond, _) => {
+ downcast_filter!(TimestampMicrosecondType, values, predicate)
+ }
+ DataType::Timestamp(Nanosecond, _) => {
+ downcast_filter!(TimestampNanosecondType, values, predicate)
+ }
+ DataType::Interval(IntervalUnit::YearMonth) => {
+ downcast_filter!(IntervalYearMonthType, values, predicate)
+ }
+ DataType::Interval(IntervalUnit::DayTime) => {
+ downcast_filter!(IntervalDayTimeType, values, predicate)
+ }
+ DataType::Interval(IntervalUnit::MonthDayNano) => {
+ downcast_filter!(IntervalMonthDayNanoType, values, predicate)
+ }
+ DataType::Duration(TimeUnit::Second) => {
+ downcast_filter!(DurationSecondType, values, predicate)
+ }
+ DataType::Duration(TimeUnit::Millisecond) => {
+ downcast_filter!(DurationMillisecondType, values, predicate)
+ }
+ DataType::Duration(TimeUnit::Microsecond) => {
+ downcast_filter!(DurationMicrosecondType, values, predicate)
+ }
+ DataType::Duration(TimeUnit::Nanosecond) => {
+ downcast_filter!(DurationNanosecondType, values, predicate)
+ }
+ DataType::Utf8 => {
+ let values = values
+ .as_any()
+ .downcast_ref::<GenericStringArray<i32>>()
+ .unwrap();
+ Ok(Arc::new(filter_string::<i32>(values, predicate)))
+ }
+ DataType::LargeUtf8 => {
+ let values = values
+ .as_any()
+ .downcast_ref::<GenericStringArray<i64>>()
+ .unwrap();
+ Ok(Arc::new(filter_string::<i64>(values, predicate)))
+ }
+ DataType::Dictionary(key_type, _) => match key_type.as_ref() {
+ DataType::Int8 => downcast_dict_filter!(Int8Type, values,
predicate),
+ DataType::Int16 => downcast_dict_filter!(Int16Type, values,
predicate),
+ DataType::Int32 => downcast_dict_filter!(Int32Type, values,
predicate),
+ DataType::Int64 => downcast_dict_filter!(Int64Type, values,
predicate),
+ DataType::UInt8 => downcast_dict_filter!(UInt8Type, values,
predicate),
+ DataType::UInt16 => downcast_dict_filter!(UInt16Type, values,
predicate),
+ DataType::UInt32 => downcast_dict_filter!(UInt32Type, values,
predicate),
+ DataType::UInt64 => downcast_dict_filter!(UInt64Type, values,
predicate),
+ t => unimplemented!("Take not supported for dictionary key
type {:?}", t),
+ },
+ _ => {
+ // fallback to using MutableArrayData
+ let mut mutable = MutableArrayData::new(
+ vec![values.data_ref()],
+ false,
+ predicate.count,
+ );
+
+ let iter = SlicesIterator::new(&predicate.filter);
+ iter.for_each(|(start, end)| mutable.extend(0, start, end));
+
+ let data = mutable.freeze();
+ Ok(make_array(data))
+ }
+ },
+ }
+}
+
+/// Computes a new null mask for `data` based on `predicate`
+///
+/// Returns `None` if no nulls in the result
+fn filter_null_mask(
+ data: &ArrayData,
+ predicate: &FilterPredicate,
+) -> Option<(usize, Buffer)> {
+ if data.null_count() == 0 {
+ return None;
+ }
+
+ let nulls = filter_bits(data.null_buffer()?, data.offset(), predicate);
+ let null_count = predicate.count - nulls.count_set_bits();
Review comment:
I'll add a comment clarifying this, the effectively it is doing
`nulls.len() - nulls.count_valid()` but as `nulls: Buffer` it needs to use a
proxy to get the "bit length". It is explicitly handling the case where the
filter is not false for a null location :sweat_smile:
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