ulysses-you opened a new pull request, #58466:
URL: https://github.com/apache/spark/pull/58466
### What changes were proposed in this pull request?
Make `RocksDB.get` and `LevelDB.get` return `null` instead of throwing
`NoSuchElementException` when a key is absent, and let the callers decide
whether a missing key is an error:
- `read` still throws `NoSuchElementException` for a missing key,
preserving the `KVStore` contract.
- `getMetadata`, the constructor, `updateBatch`, and the secondary-index
iterator path handle the `null` directly instead of catching an exception.
### Why are the changes needed?
`updateBatch` looks up the existing value via `get` before writing. During
an event-log rebuild most writes are **new** entries, so the key is absent and
`get` throws
`NoSuchElementException` on essentially every write. That exception is
immediately caught, but constructing it still fills in a full stack trace —
using exceptions for ordinary control
flow. In a History Server CPU profile this showed up as a measurable share
of CPU spent in `Throwable.fillInStackTrace` under `RocksDB.get`. Returning
`null` avoids building the exception
entirely.
### Does this PR introduce any user-facing change?
No. The public `KVStore` behavior is unchanged: `read` still throws
`NoSuchElementException` for a missing key, and `getMetadata` still returns
`null` when no metadata is present.
### How was this patch tested?
Added `testGetMissingKeyReturnsNull` to both `RocksDBSuite` and
`LevelDBSuite`, verifying that `get` returns `null` for a missing key and
returns the stored value for a present key.
Existing kvstore test suites pass.
### Was this patch authored or co-authored using generative AI tooling?
Yes. Generated-by: Claude Code.
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