ryogrid/goopg

goopg

goopg is an experimental PostgreSQL-compatible database server written in Go. It is driven entirely by coding agents as a study in agent-led implementation: can an AI agent build and evolve a meaningful PostgreSQL-like server while staying behaviourally aligned with upstream PostgreSQL?

The project has three research axes:

1. Agent-driven implementation — can coding agents produce correct, maintainable Go code for a complex stateful system, using PostgreSQL 18 as the behavioural oracle?
2. Go concurrency characteristics — how do throughput and latency scale as execution paths become more concurrent?
3. Direct I/O trade-offs — what happens when storage paths bypass the OS page cache?

This repository is research-oriented and intentionally iterative. It is not intended for production use.

The upstream PostgreSQL repository (REL_18_3) is included as a submodule under postgres/ and is used as the reference for correctness.

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Implemented Features

Wire Protocol & Connection

• PostgreSQL wire protocol v3 (simple and extended query modes)
• trust and reject authentication (pg_hba.conf)
• GUC / postgresql.conf parser with SHOW, SET, RESET
• pg_stat_activity system view

Storage & MVCC

• 8 KB heap pages in PG18-compatible on-disk format (PageHeaderData, ItemId, HeapTupleHeaderData)
• MVCC with snapshot isolation (READ COMMITTED and REPEATABLE READ)
• HOT (Heap-Only Tuple) updates — avoids index updates when non-indexed columns change
• Visibility Map — tracks all-visible pages for Index-Only Scan eligibility
• Index-Only Scan (single-column B-tree)
• Opportunistic page pruning — reclaims dead tuple chains inline during HOT updates
• VACUUM with tuple freeze (prevents XID wraparound)
• Autovacuum background worker
• Free Space Map (FSM) — guides INSERT to pages w