Align savepoint handling with MySQL semantics by chubes4 · Pull Request #496 · WordPress/sqlite-database-integration

chubes4 · 2026-08-23T21:51:02Z

What?

Align SQL savepoint handling with MySQL semantics.

A standalone SAVEPOINT in the default autocommit mode no longer opens an SQLite transaction. It is discarded immediately, so following writes use the normal BEGIN IMMEDIATE wrapper and commit independently.

Inside explicit transactions, track active savepoint names to emulate MySQL behavior for nested savepoints, reused and case-insensitive names, ROLLBACK TO, RELEASE, and missing-savepoint error 1305. Missing-savepoint errors leave the surrounding transaction active.

Add regression coverage across the MySQL-on-SQLite, concurrency, PDO API, and WordPress integration test suites.

Why?

SQLite treats a standalone SAVEPOINT as opening a transaction, but MySQL does not. Passing it through to SQLite created a hidden transaction on PHP versions before 8.4. Subsequent writes then either attempted a nested BEGIN IMMEDIATE or bypassed the normal write-locking path, depending on how the transaction state was tracked.

The original Data Machine reproduction relied on SQLite-only behavior: issuing a bare SAVEPOINT, performing a write, and committing with RELEASE SAVEPOINT. Real MySQL and MariaDB discard the standalone savepoint, so the later release reports error 1305. That downstream issue is tracked in Extra-Chill/data-machine#3436.

Note

Consumers that relied on a bare SAVEPOINT opening a transaction on SQLite must open an explicit transaction instead, matching MySQL behavior.

Fixes #495

JanJakes

@chubes4 Thanks for the PR! This looks good overall. I left one small simplification suggestion.

JanJakes · 2026-08-24T10:04:35Z

+	 * @var bool
+	 */
+	private $transaction_started_by_savepoint = false;
+


Could we use a single property by tracking only savepoints in a transaction opened by SAVEPOINT? Savepoints inside a transaction opened by BEGIN do not need tracking because releasing them cannot end the outer transaction. This would remove the need for $transaction_started_by_savepoint.

Let’s also document why this state is needed. Something like:

/** * User savepoints in a transaction opened by a SAVEPOINT statement. * * On PHP < 8.4, PDO SQLite cannot detect transactions opened with raw SQL. * Tracking the savepoint stack keeps the inTransaction() polyfill accurate * when the outermost savepoint is released. * * Savepoints inside a transaction opened by BEGIN are not tracked because * releasing them cannot end the outer transaction. * * @var string[] */ private $savepoint_transaction_stack = array();

Done. Thank you!

In MySQL, savepoints exist only within a transaction. With autocommit enabled, each statement forms its own implicit transaction, so a SAVEPOINT statement succeeds but the savepoint is discarded as soon as the statement completes. It does not start a transaction. In SQLite, a bare SAVEPOINT opens a transaction. Tracking that transaction makes the following write succeed, but it runs without a write lock, an unrelated statement error rolls it back, and it is lost entirely when the connection closes without a RELEASE. MySQL commits it. Skip the SQLite statement when no transaction is active instead, and report the MySQL error 1305 when a savepoint is referenced outside of a transaction. This makes the savepoint transaction stack unnecessary, so it is removed. MySQL and SQLite also disagree on what a savepoint name refers to. When a name is reused, MySQL deletes the original savepoint, while SQLite keeps it on the stack, shadowed by the new one. Track the savepoint names of the active transaction and resolve every ROLLBACK TO and RELEASE against them, so that a name MySQL considers deleted reports error 1305 instead of reaching the shadowed SQLite savepoint. The savepoint tests are updated accordingly: those that relied on a bare SAVEPOINT opening a transaction now open one with START TRANSACTION. Fixes WordPress#495

coderabbitai · 2026-09-01T10:40:16Z

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packages/mysql-on-sqlite/src/sqlite/class-wp-mysql-on-sqlite.php
packages/mysql-on-sqlite/tests/WP_MySQL_On_SQLite_Tests.php

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packages/mysql-on-sqlite/src/sqlite/class-wp-mysql-on-sqlite.php
packages/mysql-on-sqlite/tests/WP_MySQL_On_SQLite_Tests.php

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📝 Walkthrough

Walkthrough

The adapter now tracks normalized savepoints and preserves MySQL-compatible transaction behavior for lookup, rollback, release, errors, write locking, and cleanup. Tests cover nested operations, standalone savepoints, persistence, and transaction recovery.

Changes

Savepoint semantics

Layer / File(s)	Summary
Savepoint tracking and lifecycle `packages/mysql-on-sqlite/src/sqlite/class-wp-mysql-on-sqlite.php`	The adapter tracks normalized savepoint names, clears them at transaction boundaries, handles duplicate and nested savepoints, and raises MySQL-compatible missing-savepoint errors without rolling back the surrounding transaction.
PDO transaction and savepoint coverage `packages/mysql-on-sqlite/tests/WP_MySQL_On_SQLite_PDO_API_Tests.php`	PDO tests cover explicit transactions, nested rollback, duplicate names, case-insensitive quoted names, release behavior, and failed writes after standalone savepoints.
Regression and integration validation `packages/mysql-on-sqlite/tests/WP_MySQL_On_SQLite_Concurrency_Tests.php`, `packages/mysql-on-sqlite/tests/WP_MySQL_On_SQLite_Tests.php`, `tests/phpunit/WP_SQLite_Database_Integration_Savepoint_Test.php`	Regression and integration tests validate `BEGIN IMMEDIATE`, missing-savepoint errors, transaction cleanup, metadata operations, immediate persistence, and failed release handling.

Estimated code review effort: 3 (Moderate) | ~25 minutes

Merge Risk: ⚪ Minimal · up to 3cc53

The PR localizes transaction tracking for SQL savepoints and reports passing focused, full-suite, and coding-standard checks; no actionable merge-blocking risk remains beyond normal review.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 28.13% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 32 functions across 5 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	The changes satisfy issue `#495`. They prevent nested BEGIN IMMEDIATE calls during writes inside active savepoint transactions, preserve affected-row behavior, support savepoint release and rollback, an…
Out of Scope Changes check	✅ Passed	The code and test changes remain within the savepoint transaction-tracking scope. The added coverage directly validates the linked issue requirements and related transaction lifecycle behavior.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: aligning savepoint handling with MySQL semantics.

Full details: Linked Issues check

Explanation

The changes satisfy issue #495. They prevent nested BEGIN IMMEDIATE calls during writes inside active savepoint transactions, preserve affected-row behavior, support savepoint release and rollback, and align standalone savepoint and missing-savepoint handling with MySQL behavior.

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JanJakes · 2026-09-01T10:45:46Z

@chubes4 I had Fable review it thoroughly, and it caught that the implementation was diverging from MySQL behavior. With autocommit enabled (MySQL default), a standalone SAVEPOINT is discarded instead of opening a transaction. Tracking it as an active transaction also caused later writes to skip normal BEGIN IMMEDIATE locking, while a failed statement could roll back the entire savepoint transaction.

I pushed a follow-up commit to your branch that aligns savepoint handling with MySQL while preserving nested savepoints inside explicit transactions. If this resolves the issue you've encountered, I think we can proceed with this.

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Inline comments:
In `@packages/mysql-on-sqlite/src/sqlite/class-wp-mysql-on-sqlite.php`:
- Around line 2174-2176: Preserve the active user transaction when a missing
savepoint is reported: update the exception handling between
new_savepoint_does_not_exist_exception(),
execute_transaction_or_locking_statement(), and query() so this statement-level
error bypasses rollback_user_transaction() while still propagating the SQL
error. Ensure savepoint state and prior uncommitted writes remain intact for
callers that continue or explicitly roll back later, including both
missing-savepoint paths.

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📒 Files selected for processing (5)

packages/mysql-on-sqlite/src/sqlite/class-wp-mysql-on-sqlite.php
packages/mysql-on-sqlite/tests/WP_MySQL_On_SQLite_Concurrency_Tests.php
packages/mysql-on-sqlite/tests/WP_MySQL_On_SQLite_PDO_API_Tests.php
packages/mysql-on-sqlite/tests/WP_MySQL_On_SQLite_Tests.php
tests/phpunit/WP_SQLite_Database_Integration_Savepoint_Test.php

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MySQL error 1305 leaves the surrounding transaction and existing savepoints active. Skip the driver's automatic rollback for this error and cover both rollback and release paths.

chubes4 · 2026-09-02T11:44:45Z

I will take a look and make sure this still resolves the problem. The error was thrown during headless testing on my VPS.

chubes4 · 2026-09-02T12:34:10Z

Thanks for taking this over — your approach is right, and I wanted to confirm the premise rather than assume it.

I verified against real MariaDB 10.11 with autocommit enabled:

SELECT @@autocommit, @@in_transaction;   -- 1, 0
SAVEPOINT sp1;
SELECT @@in_transaction;                 -- 0

A bare SAVEPOINT does not open a transaction, exactly as your commit message describes. And the follow-up matches your new error path:

SAVEPOINT sp1;
UPDATE ...;
RELEASE SAVEPOINT sp1;
-- ERROR 1305 (42000): SAVEPOINT sp1 does not exist

So skipping the SQLite statement and reporting 1305 reproduces MySQL faithfully. My original patch preserved behavior MySQL never had; yours is the correct fix.

One piece of context worth recording, since it validates the change. The reproduction behind #495 came from Data Machine, which issues a bare SAVEPOINT on SQLite without an enclosing transaction and then commits with RELEASE SAVEPOINT. Against this PR head that sequence now returns 1305 on release, and on the rollback path both ROLLBACK TO SAVEPOINT and RELEASE SAVEPOINT fail while the write stays committed.

That is a latent bug on our side, not a regression here — the same sequence already fails on real MySQL, and it only appeared to work because the old adapter let a bare savepoint open a transaction. I have filed it against Data Machine (Extra-Chill/data-machine#3436); the fix is to open a real transaction instead of relying on a bare savepoint.

Flagging it only so the behavior change is understood as intentional: consumers relying on a bare SAVEPOINT opening a transaction on SQLite will now see 1305, which is what MySQL does. No changes requested from me.

chubes4 added 3 commits August 23, 2026 21:50

fix: track SQL savepoint transactions

852f068

test: avoid custom savepoint fixture table

791a7da

test: cover standalone savepoint edge cases

9879478

chubes4 mentioned this pull request Aug 23, 2026

Agent bundle loop omits required adjacent handler tool Extra-Chill/data-machine#2578

Closed

JanJakes reviewed Aug 24, 2026

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chubes4 and others added 2 commits August 24, 2026 18:38

refactor: simplify SQL savepoint tracking

48c457e

coderabbitai Bot reviewed Sep 1, 2026

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Comment thread packages/mysql-on-sqlite/src/sqlite/class-wp-mysql-on-sqlite.php

Preserve transactions after missing savepoint errors

3cc53c7

MySQL error 1305 leaves the surrounding transaction and existing savepoints active. Skip the driver's automatic rollback for this error and cover both rollback and release paths.

chubes4 mentioned this pull request Sep 2, 2026

TransactionScope issues a bare SAVEPOINT on SQLite without an active transaction Extra-Chill/data-machine#3436

Closed

JanJakes changed the title ~~Track transactions opened by SQL savepoints~~ Align savepoint handling with MySQL semantics Sep 2, 2026

JanJakes merged commit 4cfe406 into WordPress:trunk Sep 2, 2026
24 checks passed

batonac mentioned this pull request Sep 2, 2026

Sync with upstream trunk (1 commit) Avunu/sqlite-database-integration#10

Open

chubes4 mentioned this pull request Sep 2, 2026

fix: open real transactions when no boundary exists Extra-Chill/data-machine#3438

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Align savepoint handling with MySQL semantics - #496

Align savepoint handling with MySQL semantics#496
JanJakes merged 6 commits into
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chubes4:fix-495-savepoint-write-transactions

chubes4 commented Aug 23, 2026 •

edited by JanJakes

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