jecsand838 commented on code in PR #8006:
URL: https://github.com/apache/arrow-rs/pull/8006#discussion_r2248969563
##########
arrow-avro/src/reader/mod.rs:
##########
@@ -182,21 +174,130 @@ impl Decoder {
FingerprintAlgorithm::Rabin,
SchemaStore::fingerprint_algorithm,
);
+ // The loop stops when the batch is full, a schema change is staged,
+ // or handle_prefix indicates we need more bytes (Some(0)).
while total_consumed < data.len() && self.remaining_capacity > 0 {
- if let Some(prefix_bytes) =
self.handle_prefix(&data[total_consumed..], hash_type)? {
- // A batch is complete when its `remaining_capacity` is 0. It
may be completed early if
- // a schema change is detected or there are insufficient bytes
to read the next prefix.
- // A schema change requires a new batch.
- total_consumed += prefix_bytes;
- break;
+ match self.handle_prefix(&data[total_consumed..], hash_type)? {
+ None => {
+ // No prefix: decode one row.
+ let n =
self.active_decoder.decode(&data[total_consumed..], 1)?;
+ total_consumed += n;
+ self.remaining_capacity -= 1;
+ }
+ Some(0) => {
+ // Detected start of a prefix but need more bytes.
+ break;
+ }
Review Comment:
Yeah there's nothing about the wire format that prevents partial reads, the
only rule I came across is the minimum amount that can be read was one "datum"
at a time, i.e. a row's field.
> Sure, but the Some(n) case does exactly the same thing (just for a
different reason). That's why I had suggested to combine them and just use a
comment to explain what's going on.
I'm going with this approach for this PR as it's logical. I may follow-up
later with another PR to revisit some of the complexity on the `Reader` and
`Decoder`.
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