scovich commented on code in PR #8006:
URL: https://github.com/apache/arrow-rs/pull/8006#discussion_r2252866464
##########
arrow-avro/src/reader/mod.rs:
##########
@@ -124,23 +132,26 @@ fn read_header<R: BufRead>(mut reader: R) ->
Result<Header, ArrowError> {
/// A low-level interface for decoding Avro-encoded bytes into Arrow
`RecordBatch`.
#[derive(Debug)]
pub struct Decoder {
- record_decoder: RecordDecoder,
+ active_decoder: RecordDecoder,
+ active_fingerprint: Option<Fingerprint>,
batch_size: usize,
- decoded_rows: usize,
+ remaining_capacity: usize,
+ #[cfg(feature = "lru")]
+ cache: LruCache<Fingerprint, RecordDecoder>,
+ #[cfg(not(feature = "lru"))]
+ cache: IndexMap<Fingerprint, RecordDecoder>,
+ max_cache_size: usize,
+ reader_schema: Option<AvroSchema<'static>>,
+ writer_schema_store: Option<SchemaStore<'static>>,
Review Comment:
> `HeaderDecoder` seems able to get around this by parsing a json string
from the first row of an Avro file during the `ReaderBuilder::build` process
The `serde_json` code is doing [zero-copy
deserialization](https://serde.rs/lifetimes.html) from the header's byte
buffer. There's an implicit lifetime as if declared by:
```rust
pub fn schema<'a>(&'a self) -> Result<Option<Schema<'a>>, ArrowError> {
```
So the resulting schema inherits the lifetime of the header itself. AFAIK,
the only way we could get a similar effect here is to add a lifetime param to
the `Decoder`. I guess we could also try to create schemas internally, but
self-referential lifetimes tend to get really messy really fast in rust.
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