klion26 commented on code in PR #7935:
URL: https://github.com/apache/arrow-rs/pull/7935#discussion_r2218119219
##########
parquet-variant/src/builder.rs:
##########
@@ -1134,39 +1197,86 @@ impl<'a> ObjectBuilder<'a> {
)));
}
- let data_size = self.buffer.offset();
- let num_fields = self.fields.len();
- let is_large = num_fields > u8::MAX as usize;
+ let metadata_builder = self.parent_state.metadata_builder();
self.fields.sort_by(|&field_a_id, _, &field_b_id, _| {
- let key_a = &metadata_builder.field_name(field_a_id as usize);
- let key_b = &metadata_builder.field_name(field_b_id as usize);
- key_a.cmp(key_b)
+ let field_a_name = metadata_builder.field_name(field_a_id as
usize);
+ let field_b_name = metadata_builder.field_name(field_b_id as
usize);
+ field_a_name.cmp(field_b_name)
});
- let max_id = self.fields.iter().map(|(i, _)| *i).max().unwrap_or(0);
+ // the length of the metadata's field names is a very cheap to compute
the upper bound.
+ // it will almost always be a tight upper bound as well -- it would
take a pretty
+ // carefully crafted object to use only the early field ids of a
large dictionary.
+ let max_id = metadata_builder.field_names.len();
Review Comment:
IIUC, `metadata_builder.field_names.len()` returns the size of the
underlying map, it may be bigger than the actual max `field_id`, changing to
this here is that it can avoid one pass for the `field_ids` to calucalute the
`max_id`.
But this change can make test more diffict(more difficult to calculate the
header size) -- such as the failed case
`from_json::test::test_json_to_variant_object_very_large` ([test code
here](https://github.com/apache/arrow-rs/blob/82821e574df7e699c7a491da90c54429a5a439e9/parquet-variant-json/src/from_json.rs#L633)/[failed
ci](https://github.com/apache/arrow-rs/actions/runs/16401976375/job/46342711866?pr=7935))
@alamb @viirya @scovich Maybe we can revert this to the original code(travel
one pass from `filed_ids`) what do you think about this? thanks. -- added a
separate commit which reverted this logic to see if any other tests failed.
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