wyatt-herkamp commented on code in PR #27021:
URL: https://github.com/apache/datafusion/pull/27021#discussion_r4527588448
##########
datafusion/datasource-csv/src/source.rs:
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@@ -440,26 +774,46 @@ impl FileOpener for CsvOpener {
)
})?;
+ // A partition may start mid-file, so the header is fetched
+ // separately. Every byte-range partition of a file repeats
this
+ // small request; cache per file if that becomes costly.
+ let mapping = if match_by_header {
+ let header =
+ fetch_header(&config, store.as_ref(), &location,
file_size)
+ .await?;
+ // A partition starting within leading comment lines owns
+ // the header row, so it has to skip it.
+ if raw_start <= header.start as u64 {
Review Comment:
@zhuqi-lucas header ownership follows `AlignedBoundaryStream`.
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