fix(storage): add first-writer-wins write intent conflict detection for AP transactions

[liuuys]

Prevent concurrent transactions from silently overwriting each other's write intent on the same edge, which caused committed values to be lost when interleaved with an aborting transaction.

• set_edge_property_in_txn / delete_edge_in_txn: check edge.commit_ts for an external txn_id before overwriting, return WriteWriteConflict
• commit_at: validate all undo entries before setting self.commit_ts so a failed commit can still be aborted; promote all matching property versions instead of only last_mut(); return explicit errors for missing edge_id_map / block / offset mismatches
• abort: verify write intent ownership before restoring commit_ts; update edge block min_ts/max_ts on rollback
• Tests: sequential abort-restore test, sequential write-conflict test with specific error type assertion, deterministic 3-barrier concurrent test that guarantees WriteWriteConflict detection

fix(storage): add first-writer-wins write intent conflict detection for AP transactions

Type

• feat: (new feature)
• fix: (bug fix)
• docs: (doc update)
• refactor: (refactor code)
• test: (test code)
• chore: (other updates)

Scope

• query: (query engine)
  • parser: (frontend parser)
  • planner: (frontend planner)
  • optimizer: (query optimizer)
  • executor: (execution engine)
  • op: (operators)
• storage: (storage engine)
  • mvcc: (multi version concurrency control)
  • schema: (graph model and topology)
• tool: (tools)
  • cli: (cli)
  • sdk: (sdk)
• none: (N/A)

Description

Issue: #

FAIL [   0.016s] minigu-storage::integration_tests ap::transaction_test::test_concurrent_commit_and_abort_preserve_committed_value
  stdout ───

    running 1 test
    test ap::transaction_test::test_concurrent_commit_and_abort_preserve_committed_value ... FAILED

    failures:

    failures:
        ap::transaction_test::test_concurrent_commit_and_abort_preserve_committed_value

    test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 103 filtered out; finished in 0.00s
    
  stderr ───

    thread 'ap::transaction_test::test_concurrent_commit_and_abort_preserve_committed_value' (465640) panicked at minigu/storage/tests/ap/transaction_test.rs:1230:5:
    assertion `left == right` failed: Committed value should win over aborted update
      left: Some(Int32(Some(10)))
     right: Some(Int32(Some(1111)))
    note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

  Cancelling due to test failure: 7 tests still running

Checklist

• I have prepared the pull request title according to the requirements.
• I have successfully run all unit tests and integration tests.
• I have already rebased the latest master branch.
• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.

[Copilot]

Pull request overview

This PR strengthens AP MVCC transaction correctness by adding first-writer-wins detection for write intents on edges, and by hardening commit/abort bookkeeping to avoid losing committed updates under interleavings with aborting transactions.

Changes:

• Add write-write conflict detection in AP edge mutation paths so a second writer can’t overwrite an existing uncommitted write intent.
• Rework commit_at/abort to validate and enforce write-intent ownership, and to promote/rollback versions more consistently.
• Add new integration tests covering sequential abort-restore, sequential write-conflict, and a deterministic concurrent barrier scenario.

Reviewed changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated 5 comments.

File	Description
minigu/storage/src/ap/olap_graph.rs	Adds write-intent ownership checks to edge set/delete in txn to detect write-write conflicts.
minigu/storage/src/ap/transaction.rs	Validates undo entries before committing; promotes all matching property versions; adds intent-ownership checks during abort and updates block ts metadata.
minigu/storage/tests/ap/transaction_test.rs	Adds/updates tests for abort-restore behavior and write-write conflict detection, including a barrier-coordinated concurrent scenario.
.gitignore	Ignores local .claude/ files.

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