pepijnve commented on code in PR #18152:
URL: https://github.com/apache/datafusion/pull/18152#discussion_r2462741123
##########
datafusion/physical-expr/src/expressions/case.rs:
##########
@@ -122,6 +123,276 @@ fn is_cheap_and_infallible(expr: &Arc<dyn PhysicalExpr>)
-> bool {
expr.as_any().is::<Column>()
}
+/// Creates a [FilterPredicate] from a boolean array.
+fn create_filter(predicate: &BooleanArray) -> FilterPredicate {
+ let mut filter_builder = FilterBuilder::new(predicate);
+ // Always optimize the filter since we use them multiple times.
+ filter_builder = filter_builder.optimize();
+ filter_builder.build()
+}
+
+// This should be removed when https://github.com/apache/arrow-rs/pull/8693
+// is merged and becomes available.
+fn filter_record_batch(
+ record_batch: &RecordBatch,
+ filter: &FilterPredicate,
+) -> std::result::Result<RecordBatch, ArrowError> {
+ let filtered_columns = record_batch
+ .columns()
+ .iter()
+ .map(|a| filter_array(a, filter))
+ .collect::<std::result::Result<Vec<_>, _>>()?;
+ // SAFETY: since we start from a valid RecordBatch, there's no need to
revalidate the schema
+ // since the set of columns has not changed.
+ // The input column arrays all had the same length (since they're coming
from a valid RecordBatch)
+ // and the filtering them with the same filter will produces a new set of
arrays with identical
+ // lengths.
+ unsafe {
+ Ok(RecordBatch::new_unchecked(
+ record_batch.schema(),
+ filtered_columns,
+ filter.count(),
+ ))
+ }
+}
+
+#[inline(always)]
+fn filter_array(
+ array: &dyn Array,
+ filter: &FilterPredicate,
+) -> std::result::Result<ArrayRef, ArrowError> {
+ filter.filter(array)
+}
+
+///
+/// Merges elements by index from a list of [`ArrayData`], creating a new
[`ColumnarValue`] from
+/// those values.
+///
+/// Each element in `indices` is the index of an array in `values` offset by
1. `indices` is
+/// processed sequentially. The first occurrence of index value `n` will be
mapped to the first
+/// value of array `n - 1`. The second occurrence to the second value, and so
on.
+///
+/// The index value `0` is used to indicate null values.
+///
+/// ```text
+/// ┌─────────────────┐ ┌─────────┐
┌─────────────────┐
+/// │ A │ │ 0 │ merge( │
NULL │
+/// ├─────────────────┤ ├─────────┤ [values0, values1],
├─────────────────┤
+/// │ D │ │ 2 │ indices │
B │
+/// └─────────────────┘ ├─────────┤ )
├─────────────────┤
+/// values array 0 │ 2 │ ─────────────────────────▶ │
C │
+/// ├─────────┤
├─────────────────┤
+/// │ 1 │ │
A │
+/// ├─────────┤
├─────────────────┤
+/// │ 1 │ │
D │
+/// ┌─────────────────┐ ├─────────┤
├─────────────────┤
+/// │ B │ │ 2 │ │
E │
+/// ├─────────────────┤ └─────────┘
└─────────────────┘
+/// │ C │
+/// ├─────────────────┤ indices
+/// │ E │ array
result
+/// └─────────────────┘
+/// values array 1
+/// ```
+fn merge(values: &[ArrayData], indices: &[usize]) -> Result<ArrayRef> {
Review Comment:
> I was confused by the example that only shows values 0 and 1 -- I see now
this works for an arbitrary number of input arrays (more than 2)
That one I can solve easily. I'll make the example a bit more representative
of the general case I'm trying to solve. It'll look less like zip then.
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