scovich commented on code in PR #9685:
URL: https://github.com/apache/arrow-rs/pull/9685#discussion_r3064960913
##########
parquet-variant-compute/src/from_json.rs:
##########
@@ -26,12 +26,21 @@ use parquet_variant_json::JsonToVariant;
/// Macro to convert string array to variant array
macro_rules! string_array_to_variant {
($input:expr, $array:expr, $builder:expr) => {{
- for i in 0..$input.len() {
- if $input.is_null(i) {
- $builder.append_null();
- } else {
+ let len = $input.len();
+ let mut i = 0;
+ while i < len {
Review Comment:
It's not obvious to me that this is a good use of `append_nulls` -- it takes
almost as much work to detect runs as to just append the nulls directly, so
we're likely slowing down the loop by up to 2x in almost all cases even if we
ignore the extra branching (and branch mispredictions) of this more complex
control flow.
##########
parquet-variant-compute/src/variant_array_builder.rs:
##########
@@ -156,6 +156,26 @@ impl VariantArrayBuilder {
self.value_offsets.push(self.value_builder.offset());
}
+ /// Appends `count` null rows to the builder.
+ pub fn append_nulls(&mut self, count: usize) {
+ if count == 0 {
+ return;
+ }
+ if count == 1 {
Review Comment:
I'd suggest following whatever e.g. `StructBuilder` does. If that approach
hasn't caused any performance issues there, it probably works fine here as
well. Plus, there's something to be said for uniformity of implementations.
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