PGMQ (PostgreSQL Message Queue) is a production-grade message queue implemented as a PostgreSQL extension, with a first-class Rust client library. The system provides SQS-style queue operations (send, read, pop, delete, archive, set visibility timeout) entirely within PostgreSQL, using FOR UPDATE SKIP LOCKED for concurrency. It supports FIFO ordering with message group keys, topic-based routing with wildcard patterns, partitioned queues (via pg_partman), unlogged tables for write throughput, and LISTEN/NOTIFY integration with configurable throttling. The Rust client (pgmq-rs) abstracts queue operations behind a generic Queue trait, with implementations for multiple database drivers: sqlx, Diesel (sync and async), rust-postgres, and tokio-postgres. The extension ships with a comprehensive SQL migration system supporting versioned upgrades, a CLI tool for installation, and extensive test coverage including regression tests and client integration tests. The architecture is layered: the PostgreSQL extension provides the core SQL functions and tables, while the Rust client offers a type-safe, async API. This hybrid approach allows users to interact with queues either directly via SQL or through the client library.
VexDB-Lite is a vector similarity search library providing Approximate Nearest Neighbor (ANN) capabilities as extensions for PostgreSQL, DuckDB, and SQLite databases. The system implements Hierarchical Navigable Small World (HNSW) graphs for efficient similarity search, with optional Product Quantization and RaBitQ compression for memory efficiency. It features hardware-accelerated distance computation using SIMD instructions (SSE, AVX, AVX512, NEON) and provides multiple distance metrics (L2, inner product, cosine). The architecture separates core algorithms from database-specific adapters, enabling consistent functionality across different storage engines. The codebase demonstrates strong engineering practices with reusable components like the SIMD dispatch system, vector buffer manager, and product quantization implementation.
pg_mooncake is a Postgres extension that adds a custom table access method ('mooncake') backed by Apache Iceberg, enabling real-time analytics on columnar data stored in Iceberg tables. It integrates DuckDB (via pg_duckdb) as the query engine for fast analytics and provides a background worker (moonlink) that streams changes from regular Postgres heap tables to Iceberg tables via logical replication, ensuring sub-second data freshness. The extension exposes SQL procedures to create columnstore mirrors of Postgres tables, manage snapshots, load files, and optimize storage. It is built using the pgrx framework for Rust-based Postgres extensions and supports Postgres versions 14-18. The architecture is a hybrid of a shared library loaded into the Postgres backend and a separate background worker process. The codebase is well-structured and actively developed, though many table access method callbacks are still stubs, indicating it is in an early but functional stage.