Add PostgreSQL support for rollback backend by johnnyjoy · Pull Request #16757 · luanti-org/luanti

johnnyjoy · 2025-12-17T19:06:00Z

Adds PostgreSQL as an optional backend for the rollback system, complementing the existing SQLite3 implementation. The rollback backend is configurable per-world via rollback_backend in world.mt, defaulting to sqlite3 when unset.

Changes

New PostgreSQL rollback backend (RollbackMgrPostgreSQL) with feature parity to SQLite3
Strict configuration: requires explicit pgsql_rollback_connection when PostgreSQL is selected (no fallback to map backend)
Shared base class (RollbackMgr) to eliminate code duplication between backends
Refactored initialization: extracted rollback manager creation from Server::init() into Server::createRollbackManager()
PostgreSQL 9.5+ requirement: enforces minimum version
Documentation updates: doc/world_format.md and builtin/settingtypes.txt updated

Configuration

Set in world.mt:

rollback_backend = postgresql (or sqlite3)
pgsql_rollback_connection = "host=... dbname=..." (required when using PostgreSQL)

Development Process

This PR was developed with assistance from Cursor and LLM tools for code generation and refactoring. All changes have been reviewed against project coding standards, and feedback from maintainers (sfan5, SmallJoker) has been incorporated throughout the development process.

sfan5

The rollback code is a bit neglected, but surprisingly many people still use it and I guess adding another backend is okay.

CMakePresets.json

doc/world.mt.rollback_postgresql.example

minetest.conf.example

src/server.cpp

src/server/rollback_postgresql.cpp

src/server/rollback.cpp

src/server/rollback.h

src/server/rollback.cpp

src/server/rollback_postgresql.cpp

src/server/rollback_sqlite3.cpp

builtin/settingtypes.txt

doc/lua_api.md

src/server.cpp

src/server/rollback_postgresql.h

src/server/rollback_sqlite3.cpp

src/server/rollback.cpp

src/server/rollback_postgresql.cpp

src/server/rollback.h

SmallJoker · 2026-03-01T07:33:21Z

src/server/rollback_sqlite3.cpp

@@ -0,0 +1,815 @@
+// Luanti


Note to reviewers: as of 2026-03-01, this file is identical to the old rollback.cpp but with renamed class name. (This is good. Shared code can be unified later.)

SmallJoker · 2026-03-01T07:38:05Z

src/server/rollback_sqlite3.h

@@ -0,0 +1,88 @@
+// Luanti


Note to reviewers: as of 2026-03-01, this file is identical to the old rollback.h but with renamed class name.

src/server/rollback.cpp

Extract the large cache loading blocks from RollbackManagerPostgreSQL constructor into loadActorCache() and loadNodeCache() helper methods. This reduces the constructor from ~33 lines to 5 lines, addressing sfan5's feedback about large code blocks.

Co-authored-by: SmallJoker <SmallJoker@users.noreply.github.com>

Improve error handling in Server::createRollbackManager - Throw exception if world.mt cannot be read, matching openModStorageDatabase pattern - Remove unused backend_source variable and simplify logging - Simplify backend selection using world_mt.getNoEx() instead of if-else block Enhance error messages and help output - Add Server::getRollbackBackends() to dynamically list available backends - Use dynamic backend list in error message for unsupported backends - Add rollback backends to print_help() output in main.cpp - Remove redundant USE_POSTGRESQL=OFF specific error message Improve destructor safety and consistency - Move db != nullptr check from SQLite destructor to flush() method - Move initialized() check from PostgreSQL destructor to flush() method - Ensures consistent safety checks across both backends Restore spacing alignment for readability - Add space padding after sqlite3_bind_* function names - Matches existing pattern in rollback_sqlite3.cpp Rename RollbackManager to RollbackMgr for line length compliance - Use RollbackMgr abbreviation following existing codebase patterns - Rename RollbackManager → RollbackMgr - Rename RollbackManagerSQLite3 → RollbackMgrSQLite3 - Rename RollbackManagerPostgreSQL → RollbackMgrPostgreSQL - Break long function signatures to ensure all lines are under 95 characters

…ng bool The original code would throw std::out_of_range when substr() was called with npos, making the fallback code that bound 0,0,0 unreachable dead code. This change makes parseNodemetaLocation() throw std::invalid_argument on invalid format, matching the original behavior and eliminating the dead code. Changes: Change parseNodemetaLocation() signature from bool to void Throw std::invalid_argument exceptions instead of returning false Remove unreachable fallback blocks in SQLite and PostgreSQL backends Add #include <stdexcept> to rollback.cpp This addresses SmallJoker's feedback.

Address SmallJoker's request for unit tests to verify that parseNodemetaLocation() correctly throws std::invalid_argument on invalid format. Tests cover: Valid format parsing (basic, negative, zero coordinates) Invalid format exceptions (missing prefix, missing commas, empty string)

…greSQL

Zughy added @ Startup / Config / Util Feature ✨ PRs that add or enhance a feature Roadmap: Needs approval The change is not part of the current roadmap and needs to be approved by coredevs beforehand labels Dec 17, 2025

sfan5 requested changes Dec 18, 2025

View reviewed changes

sfan5 self-requested a review December 19, 2025 19:36

sfan5 added Roadmap: supported by core dev PR not adhering to the roadmap, yet some core dev decided to take care of it and removed Roadmap: Needs approval The change is not part of the current roadmap and needs to be approved by coredevs beforehand labels Dec 19, 2025

sfan5 reviewed Dec 25, 2025

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sfan5 self-requested a review December 27, 2025 21:27

SmallJoker reviewed Dec 28, 2025

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Zughy added the Action / change needed Code still needs changes (PR) / more information requested (Issues) label Dec 28, 2025

SmallJoker self-requested a review December 28, 2025 20:24

Zughy removed the Action / change needed Code still needs changes (PR) / more information requested (Issues) label Dec 29, 2025

SmallJoker reviewed Dec 31, 2025

View reviewed changes

src/server/rollback.cpp Outdated Show resolved Hide resolved

src/server/rollback.cpp Outdated Show resolved Hide resolved

src/server/rollback_postgresql.cpp Outdated Show resolved Hide resolved

src/server/rollback_postgresql.cpp Outdated Show resolved Hide resolved

Zughy added the Action / change needed Code still needs changes (PR) / more information requested (Issues) label Dec 31, 2025

johnnyjoy force-pushed the pr/rollback-postgresql branch from 058d001 to ddcb9a3 Compare January 1, 2026 18:40

sfan5 requested a review from SmallJoker January 7, 2026 16:04

johnnyjoy force-pushed the pr/rollback-postgresql branch 2 times, most recently from 94cb80a to 65adda1 Compare January 13, 2026 15:30

Zughy removed the Action / change needed Code still needs changes (PR) / more information requested (Issues) label Jan 13, 2026

johnnyjoy force-pushed the pr/rollback-postgresql branch 2 times, most recently from 067d444 to 2c7b830 Compare January 24, 2026 15:24

johnnyjoy force-pushed the pr/rollback-postgresql branch 3 times, most recently from 8c55343 to 64db4d7 Compare February 4, 2026 02:53

johnnyjoy force-pushed the pr/rollback-postgresql branch 3 times, most recently from 8977aa3 to e98362c Compare February 13, 2026 01:54

johnnyjoy force-pushed the pr/rollback-postgresql branch from e98362c to 6316eaa Compare February 14, 2026 13:22

johnnyjoy force-pushed the pr/rollback-postgresql branch from 6316eaa to b060d38 Compare February 25, 2026 15:04

johnnyjoy force-pushed the pr/rollback-postgresql branch 2 times, most recently from 767a383 to ac8bbbc Compare March 1, 2026 03:53

SmallJoker reviewed Mar 1, 2026

View reviewed changes

SmallJoker self-requested a review March 4, 2026 20:48

johnnyjoy and others added 14 commits March 8, 2026 20:13

Add PostgreSQL support for rollback backend

39c83c4

Made changes suggest by sfan5 and addition cleanup

0b45858

Removed edit of minetest.conf.example, and removed support for PG < v9.5

0ada3f9

Update builtin/settingtypes.txt

1561b11

Co-authored-by: SmallJoker <SmallJoker@users.noreply.github.com>

Update doc/lua_api.md

13a81c7

Co-authored-by: SmallJoker <SmallJoker@users.noreply.github.com>

Reverted RollbackMgrSQLite3 and Remove indirection in RollbackMgrPost…

5abe194

…greSQL

Fixed whitespace issue.

0a7d650

Reverse edit of minetest.conf.example

dc2dc9c

RollbackMgr::getNodeActors: keep original code order per SmallJoker

c0d79f9

Fixed incorrect white space in PR files.

fe6a7e5

johnnyjoy force-pushed the pr/rollback-postgresql branch from 7bb1370 to fe6a7e5 Compare March 9, 2026 00:13

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johnnyjoy commented Dec 17, 2025 •

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SmallJoker Mar 1, 2026 •

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