Core concepts, v0.1.0 docs, PLOMID

diagram

flowchart TB
    SQL["one SQL"] --> REL["relational rows"]
    SQL --> DOC["JSON documents"]
    SQL --> TS["time-series events"]
    REL --- MVCC["versioned rows\n+ MVCC snapshots"]
    DOC --- MVCC
    TS --- MVCC
    MVCC --> WAL["WAL-first persistence"]

Diagram source · mermaidcopy included

mermaidsource

flowchart TB
    SQL["one SQL"] --> REL["relational rows"]
    SQL --> DOC["JSON documents"]
    SQL --> TS["time-series events"]
    REL --- MVCC["versioned rows\n+ MVCC snapshots"]
    DOC --- MVCC
    TS --- MVCC
    MVCC --> WAL["WAL-first persistence"]

1. Everything is SQL-first#

SQL text → tokens (crates/sql/src/lexer.rs) → AST (ast.rs) → execution (crates/executor). There is no separate NoSQL API. JSON and time-series are column types and operators inside SQL, not side systems. See Query pipeline.

2. Data lives in versioned rows#

Writes create row versions tagged with transaction ID + commit timestamp (crates/mvcc). Readers see a snapshot (watermark + active set). Your own writes are always visible to you; concurrent committed writes become visible according to snapshot rules. See MVCC.

3. Persistence is WAL-first#

Every write is appended to the WAL (PLW2 records) and fsync'd at commit before pages are updated. Checkpoints bound replay. After a crash, recovery replays strictly after the checkpoint boundary. See WAL / checkpoints / recovery.

4. Indexes are access paths, not storage#

Tables are the authority. B-tree indexes (persistent) enforce uniqueness and serve equality/range/order; in-memory ART indexes serve transient coordination. The v0.1.0 planner surface reports sequential scans via EXPLAIN — index usage is explicit in executor paths, not a cost-based choice. See Indexes.

5. Types are PostgreSQL-shaped#

int2/4/8, float4/8, numeric, text/varchar, bool, date/time/timestamptz/interval, uuid, json/jsonb, arrays, inet, ranges, plus serial pseudo-types and user ENUM/DOMAIN/composite. OIDs match PostgreSQL 17 for wire compatibility. See Types.

6. Errors are explicit#

Parse errors (crates/sql/src/parser/mod.rs:ParseError::Unsupported), execution errors (crates/executor/src/error.rs), storage corruption (ErrorKind::Corruption), transaction conflicts (ErrorKind::Transaction/Conflict). No silent coercion surprises — see Errors and NULL semantics.

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Core concepts