etseidl commented on code in PR #6999:
URL: https://github.com/apache/arrow-rs/pull/6999#discussion_r1922751295
##########
parquet/src/file/metadata/reader.rs:
##########
@@ -1052,5 +1060,17 @@ mod async_tests {
.unwrap();
assert_eq!(fetch_count.load(Ordering::SeqCst), 1);
assert!(metadata.offset_index().is_some() &&
metadata.column_index().is_some());
+
+ // Prefetch more than enough
+ fetch_count.store(0, Ordering::SeqCst);
+ let f = MetadataFetchFn(&mut fetch);
+ let metadata = ParquetMetaDataReader::new()
+ .with_page_indexes(true)
+ .with_prefetch_hint(Some(len)) // prefetch entire file
Review Comment:
Might as well add a test with `prefetch > 130650` but less than file size.
##########
parquet/src/file/metadata/reader.rs:
##########
@@ -409,10 +409,21 @@ impl ParquetMetaDataReader {
None => return Ok(()),
};
- let bytes = match &remainder {
- Some((remainder_start, remainder)) if *remainder_start <=
range.start => {
- let offset = range.start - *remainder_start;
- remainder.slice(offset..range.end - *remainder_start + offset)
+ let bytes = match &fetched {
+ Some((fetched_start, fetched)) if *fetched_start <= range.start =>
{
+ // `fetched`` is an amount of data spanning from fetched_start
to the end of the file
+ // We want to slice out the range we need from that data, but
need to adjust the
+ // range we are looking for to be relative to fetched_start.
+ let fetched_start = *fetched_start;
+ let range = range.start - fetched_start..range.end -
fetched_start;
+ // santity check: `fetched` should always go until the end of
the file
+ // so if our range is beyond that, something is wrong!
+ assert!(
+ range.end <= fetched_start + fetched.len(),
+ "range: {range:?}, fetched: {}, fetched_start:
{fetched_start}",
+ fetched.len()
+ );
+ fetched.slice(range)
Review Comment:
```suggestion
let offset = range.start - *remainder_start;
let end = offset + range.end - range.start;
assert!(end <= remainder.len());
remainder.slice(offset..end)
```
Instead of all the other changes, I think this will properly compute the end
of the slice.
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