Notes for PostgreSQL users

flowchart LR
    subgraph Stay["stays the same"]
        C["psql, drivers,\nconnection strings"]
        S["familiar SQL\n+ type names"]
        CT["pg_catalog\nintrospection"]
    end
    subgraph Change["changes"]
        E["PLOMID's own\nexecutor + planner"]
        TX["single-writer\nMVCC snapshots"]
        OP["own CLI,\ncheckpoints, WAL"]
    end
    Stay -.- Change

flowchart LR
    subgraph Stay["stays the same"]
        C["psql, drivers,\nconnection strings"]
        S["familiar SQL\n+ type names"]
        CT["pg_catalog\nintrospection"]
    end
    subgraph Change["changes"]
        E["PLOMID's own\nexecutor + planner"]
        TX["single-writer\nMVCC snapshots"]
        OP["own CLI,\ncheckpoints, WAL"]
    end
    Stay -.- Change

Similar (verified)#

• Wire protocol v3: psql, DBeaver, psycopg/pg drivers connect unchanged; simple + extended query, $1 params, pg_catalog/information_schema introspection.
• Type names + OIDs mirror PG 17 (int4=23, jsonb=3802, …); server_version 17.0; familiar SQLSTATEs (28P01, 08P01).
• serial sequences, ENUM/DOMAIN, RETURNING, ON CONFLICT, windows, CTEs, set ops.

Different#

• Engine is PLOMID's own: EXPLAIN shows scan shapes, no cost planner; ILIKE case-folding ignored single-table; NULL AND TRUE → false (is-true logic, not strict 3VL).
• Single-writer + MVCC snapshots; isolation options parse but don't select a PG isolation implementation.
• FOREIGN KEY unenforced; file COPY rejected; UPDATE…FROM/COPY not in explicit txns; LIMIT/OFFSET literal-only.
• Three password defaults exist (server plomid, CLI/start.sh secret) — set explicitly.
• TLS flags parse but handshake declined; binary wire values unsupported (text only).

Assumptions to drop#

PostgreSQL-compatible as a blanket claim; planner hints; procedural languages; replication/slots beyond catalog rows; performance parity numbers. When in doubt: Compatibility.