apache / apache/parquet-java

Vectored Parquet reads can fall back unsafely after partial asynchronous reads and exceed allocation limits

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Beschreibung

### Describe the bug, including details regarding any error messages, version, and platform.

`ParquetFileReader` can produce unsafe fallback behavior when Hadoop vectored I/O
is enabled and a filesystem partially submits or completes a vectored read before
raising `IllegalArgumentException` or `UnsupportedOperationException`.

The current implementation catches those exceptions around `readVectored(...)`
and retries every range using ordinary reads against the same `ChunkListBuilder`.
If an earlier range already populated the builder, its data is appended again.
For a filtered column with selected pages `P0` and `P2`, the buffered page
sequence can become `[P0, P0, P2]` although the page index still describes
`[P0, P2]`. Depending on the page contents, decoding can fail or silently
associate the wrong page with the selected rows. Even when no page has been
consumed yet, scalar fallback is unsafe once sibling asynchronous reads may still
be operating on the same stream.

Current upstream code:

https://github.com/apache/parquet-java/blob/8e30c4cee3c7e85a8cf2133697f13138509b05b7/parquet-hadoop/src/main/java/org/apache/parquet/hadoop/ParquetFileReader.java#L1293-L1307

The same vectored path also allocates one buffer for an entire contiguous
requested range instead of honoring `parquet.read.allocation.size` (8 MiB by
default), unlike the ordinary read path. Large projected column chunks or
filtered pages can therefore create unexpectedly large heap allocations.

The current `master` branch and Apache Parquet Java 1.18.0 contain this behavior.
The vulnerable path is also present in the 1.15.x, 1.16.x, and 1.17.x release
lines. Vectored I/O defaults to enabled starting in 1.16.0, so supported Hadoop
filesystems can reach this path without an explicit opt-in; in 1.15.2 it is
reachable when explicitly enabled.

Expected behavior:

- Preserve ordinary fallback only when vectored I/O is unavailable or range
preparation fails before asynchronous submission starts.
- Once submission begins, fail the read safely rather than replaying scalar reads
against a partially populated builder or an active stream.
- Wait for already-published sibling reads before returning the original failure.
- Split filesystem byte ranges to respect the configured allocation limit without
changing the logical read plan or decoded results.
- Add regression coverage for partial submission/completion, pending sibling
futures, filtered pages, oversized columns, and checksum-enabled reads.

### Component(s)

parquet-hadoop

Beitragsleitfaden

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Rechercherichtung

Beginne in parquet-hadoop's ParquetFileReader.java am Vektor-Leseweg um die Zeilen 1293-1307, verfolge dann ChunkListBuilder, asynchrone Geschwisterlesevorgänge und die Verarbeitung von parquet.read.allocation.size. Füge Regressionstests für teilweise Übermittlung oder Fertigstellung, ausstehende Geschwister-Futures, gefilterte Seiten, übergroße Spalten und lesende Vorgänge mit aktivierter Prüfsumme hinzu; die Arbeit ist abgeschlossen, wenn ein sicheres Fehlschlagen oder Fallback sowie begrenzte Allokationen gewährleistet sind, ohne die dekodierten Ergebnisse zu verändern.

Vom Indexierungsmodell aus dem Issue-Text verfasst.

Bewertung

Tech-Stack
java
Bereich
data-engineering
Issue-Typ
Bug
Schwierigkeit
4/5
Geschätzter Aufwand
3-5 Tage
Aktivitätsstatus
Ruhig
Klarheit
Klar beschrieben
Anfängerfreundlichkeit
45/100

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