[PR] Fix ObjectWriter accepting segment offsets beyond EOF [iotdb]

["hongzhi-gao (via GitHub)" <gi...@apache.org>]

hongzhi-gao opened a new pull request, #18907:
URL: https://github.com/apache/iotdb/pull/18907

   ## Description
   
   ObjectWriter previously accepted consensus writes whose offset exceeded the file length. FileChannel.truncate does not extend the file, so positioning and writing at that offset could leave a zero-filled gap instead of the missing segment contents.
   
   Reject offsets beyond EOF with the existing IOException before truncating, repositioning, or writing. Preserve sequential appends, consensus rollback/rewrite, offset-zero overwrite, and rejection of ordinary nonzero rollback. Reuse the existing localized error message and leave the shared truncation helper unchanged.
   
   Add two JUnit tests using real temporary files and byte-content assertions. They cover missing first/middle segments for ordinary and consensus requests, unchanged contents after rejection, appending after filling the gap, and valid rewrites/appends/overwrites after reopening.
   
   ### Validation
   
   Executed on JDK 17:
   
   ```sh
   mvn spotless:apply -o -pl iotdb-core/datanode -Ddevelocity.off=true
   mvn test -o -pl iotdb-core/datanode -am -Dtest=ObjectWriterTest -Dsurefire.failIfNoSpecifiedTests=false -DfailIfNoTests=false -Ddevelocity.off=true
   git diff --check
   ```
   
   Formatting and diff checks passed. The reactor command compiled main/test sources and passed both tests (0 failures, 0 errors, 0 skipped). Running the same tests against the original implementation failed the missing-segment test because a consensus write beyond EOF did not throw IOException; the rewrite test passed.
   
   The initial single-module test command (`mvn test -o -pl iotdb-core/datanode -Dtest=ObjectWriterTest -Ddevelocity.off=true`) failed during compilation because installed dependencies lacked interfaces used by the current sources. The reactor command above resolved this mismatch.
   
   No cluster IT was added: DataExecutionVisitor.visitWriteObjectFile still throws UnsupportedOperationException, and no ObjectWriter instantiation was found in production sources. These tests establish the underlying file-writer behavior, not an end-to-end Apache cluster corruption scenario. No format, protocol, locking, WAL, snapshot, or resource-lifecycle change is introduced; performance was not benchmarked.
   
   <hr>
   
   This PR has:
   
   - [x] been self-reviewed.
   - [x] added unit tests covering the changed behavior with real files.
   
   <hr>
   
   ##### Key changed/added classes
   
   - ObjectWriter
   - ObjectWriterTest
   


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Re: [PR] Fix ObjectWriter accepting segment offsets beyond EOF [iotdb]

["jt2594838 (via GitHub)" <gi...@apache.org>]

jt2594838 merged PR #18907:
URL: https://github.com/apache/iotdb/pull/18907


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