[KevinBlakeLopez]

Description

Fixes #10649.

InnoDB errno 1213 rolls the victim transaction back. CodeIgniter left transDepth at 1, so the next write on that connection autocommitted. transComplete() returned false and did not remove that write. transCommit() called mysqli::commit(), which returns true, and reported success while the victim row was already gone.

This is only errno 1213. Errno 1205 is not handled here, because innodb_rollback_on_timeout decides whether InnoDB rolled that transaction back.

After 1213, the next statement on that connection starts a new server transaction, so it does not autocommit. transCommit() returns false without calling mysqli::commit(). transComplete() still sees the failed status and rolls the new server transaction back.

On develop (df8b96bee) the new live tests failed before this change. transCommit():

-    'visible_before' => [],
-    'finished' => false,
-    'visible_after' => [],
+    'visible_before' => [102],
+    'finished' => true,
+    'visible_after' => [102],

transComplete() already returned false, and the following row stayed visible:

-    'visible_before' => [],
+    'visible_before' => [102],
     'finished' => false,
-    'visible_after' => [],
+    'visible_after' => [102],

The victim id 101 was absent in both runs. After the change, DeadlockTransactionTest passes, and the existing TransactionTest, TransactionDBDebugTrueTest, and TransactionDBDebugFalseTest still pass (local MySQL 8.0.45, PHP 8.5.12, MySQLi).

Checklist:

• Securely signed commits
• Component(s) with PHPDoc blocks, only if necessary or adds value (without duplication)
• Unit testing, with >80% coverage
• User guide updated
• Conforms to style guide

Made with Cursor

[carson-codeigniter4]

Hi there, @KevinBlakeLopez! 👋

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[Copilot]

🟡 Changes recommended

Prepared statements and failed transaction restarts can still allow subsequent writes to autocommit.

3 open issues

• Clear restart flag only after successful transaction begin · New
• Apply deadlock recovery handling to prepared statement execution · New
• Restore probe-table cleanup marker after deadlock recovery · New

What changed in this PR

Addresses #10649 by tracking MySQLi transactions rolled back by deadlock error 1213, preventing later writes from autocommitting and avoiding false commit success. Reviewed under the assumed develop patch-release policy.

Changes:

• Adds rollback tracking, deferred transaction restart, and commit protection.
• Adds live MySQLi deadlock regression tests.
• Documents recovery behavior while leaving error 1205 unchanged.

Validation used targeted source inspection; live database tests and full validation remain with CI.

File	Description
user_guide_src/​source/​database/​transactions.rst	Documents MySQL deadlock recovery behavior.
user_guide_src/​source/​changelogs/​v4.7.6.rst	Records the errno 1213 fix.
tests/​system/​Database/​Live/​MySQLi/​DeadlockTransactionTest.php	Adds deadlock and subsequent-write regression tests.
system/​Database/​MySQLi/​Connection.php	Detects deadlocks and restarts server transactions.
system/​Database/​BaseConnection.php	Tracks server rollback state and prevents false commit success.

_{Review effort: Balanced}

[KevinBlakeLopez]

Fixed in 8089966. begin_transaction() now runs inside the try, and the restart flag is cleared only after it succeeds. A failed BEGIN goes through the normal error path, so query() returns false or throws DatabaseException as usual, and ping()/reconnect() work. testLostConnectionAfterDeadlockDoesNotEscapeAsDriverException kills the connection after the 1213 and covers it.

Same commit, one more change: when the server has rolled the transaction back, transCommit() now rolls back the restarted server transaction before returning false. Before, it left transDepth at 1, so a caller that retried without transRollback() nested inside the open transaction, got true from transCommit(), and nothing was committed. testFalseTransCommitEndsTheTransactionSoARetryCommits covers it.

[KevinBlakeLopez]

Not changed in this PR. Prepared statements are left out on purpose to keep the change small. In 8089966 the guide and changelog now say so: the fix covers query(), simpleQuery() and the Query Builder, and prepared queries are not covered. PreparedQuery::_execute() can be handled in a separate PR.

[KevinBlakeLopez]

Fixed in 8089966. resetProbe() records the table before recreating it, so teardown drops it, including when setup fails.