pgGraph is a PostgreSQL extension written in Rust (via pgrx) that adds high-performance graph query capabilities directly into PostgreSQL. It allows users to model graphs by registering existing relational tables as nodes and edges, building a compressed sparse row (CSR) adjacency index for sub-millisecond traversals, shortest paths, and connected components. The extension exposes SQL functions (`graph.traverse`, `graph.shortest_path`, `graph.search`, `graph.gql`, `graph.cypher`) and supports both openCypher and a subset of GQL for querying property graphs. It integrates deeply with PostgreSQL security (row-level security, multi-tenancy, ACLs), provides resource governance (memory, disk, work unit budgets), and includes a durable projection layer with atomic manifests, delta segments, compaction, and crash recovery. The codebase is structured as a pgrx extension with a Rust core, SQL bootstrap scripts, background workers for build/maintenance jobs, and an extensive test suite including fuzz targets, property-based tests, and heavy integration tests for concurrency, crash recovery, and performance gates.
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.