mq-db

Markdown-specialized embedded database with interval-indexed block storage and hierarchical query support.

mq-db treats Markdown documents as structured, hierarchical databases rather than plain text. It parses Markdown into a flat block list with an interval index (Nested Set / Pre-Post Order), enabling O(1) section hierarchy queries. Documents can be queried with SQL or mq and persisted to a compact custom page-file format.

flowchart TD
    A["Markdown File(s)"] -->|"CST Parser (mq-markdown)"| B["Block Tree\n(heading · paragraph · code · list …)"]
    B -->|"Interval Index + Secondary Indexes"| C["Flat Block Vector\n(pre/post integers)"]
    C --> D["BitmapIndex\n(block_type)"]
    C --> E["BTreeIndex\n(pre / post)"]
    C --> F["HashIndex\n(content / lang / depth)"]
    C --> G["Zone Maps\n(per-document stats)"]
    C --> H["SQL Engine\n(sqlparser — custom native evaluator)"]
    C --> I["mq Engine\n(mq-lang evaluator)"]

Important

This project is under active development and the API may change.

Features

Flat block storage — every Markdown element becomes a typed Block with row-polymorphic properties
O(1) hierarchy queries — interval index (pre/post) makes ancestor/descendant checks a single integer comparison
Three-layer secondary indexes — BitmapIndex (block type), BTreeIndex (pre/post), HashIndex (content/lang/depth) for fast SQL predicate pushdown
Zone Maps — per-document statistics skip irrelevant files before scanning any blocks
Dual query engines — SQL via a custom sqlparser-based evaluator, and mq via mq-lang
DDL support — CREATE TABLE, INSERT INTO, DROP TABLE for in-memory custom tables
mq() scalar function — run an mq program against Markdown content inline in SQL
Custom page-file persistence — 8 KB fixed pages, checksums, atomic writes
CLI + interactive REPL + TUI — full terminal experience

Installation

Using the Installation Script (Recommended)

curl -fsSL https://raw.githubusercontent.com/harehare/mq-db/main/bin/install.sh | bash

The installer will:

Download the latest release for your platform
Verify the binary with SHA256 checksum
Install to ~/.local/bin/
Update your shell profile (bash, zsh, or fish)

After installation, restart your terminal or run:

source ~/.bashrc  # or ~/.zshrc, or ~/.config/fish/config.fish

Using Cargo

cargo install mq-db

From Source

# Latest Development Version
cargo install --git https://github.com/harehare/mq-db.git

Supported Platforms

Linux: x86_64, aarch64
macOS: x86_64 (Intel), aarch64 (Apple Silicon)
Windows: x86_64

CLI Usage

Index Markdown files

mq-db index docs/ --recursive --output store.mq-db
mq-db index README.md DESIGN.md
mq-db index docs/ --no-spans   # omit source spans (~21 bytes/block saved)

  ✓ docs/DESIGN.md
  ✓ docs/API.md

Indexed 2 files → store.mq-db

List indexed documents

mq-db list --db store.mq-db
mq-db list --db store.mq-db --format json   # also: csv, tsv, markdown, html

┌──────┬────────────────────────────────────────────────────┬────────┬──────────┐
│   ID │ Path / Title                                       │ Blocks │ Tags     │
├──────┼────────────────────────────────────────────────────┼────────┼──────────┤
│    0 │ docs/DESIGN.md                                     │    142 │          │
│    1 │ docs/API.md                                        │     87 │ api, v2  │
└──────┴────────────────────────────────────────────────────┴────────┴──────────┘
2 documents

SQL queries

mq-db sql "SELECT block_type, count(*) FROM blocks GROUP BY block_type" --db store.mq-db
mq-db sql --file query.sql --db store.mq-db           # read SQL from a file
mq-db sql "SELECT ..." --db store.mq-db --format json  # also: csv, tsv, markdown, html

┌─────────────┬──────────┐
│ block_type  │ count(*) │
├─────────────┼──────────┤
│ paragraph   │ 48       │
│ heading     │ 21       │
│ code        │ 15       │
└─────────────┴──────────┘
(3 rows)

Hierarchy query with under() — find all content inside a specific section:

mq-db sql "
  SELECT b.block_type, b.content
  FROM blocks b
  WHERE under(b.pre, b.post,
    (SELECT pre FROM blocks WHERE block_type = 'heading' AND content = 'Architecture'),
    (SELECT post FROM blocks WHERE block_type = 'heading' AND content = 'Architecture'))
  ORDER BY b.pre
" --db store.mq-db

mq() scalar function — run an mq program against Markdown content inline:

mq-db sql "SELECT mq('.h1 | to_text', content) AS title FROM blocks WHERE block_type = 'code'" --db store.mq-db

DDL — custom in-memory tables

# Create from a SELECT result
mq-db sql "CREATE TABLE headings AS SELECT content, depth FROM blocks WHERE block_type = 'heading'" --db store.mq-db

# Create with explicit schema, then insert
mq-db sql "CREATE TABLE notes (id TEXT, body TEXT)" --db store.mq-db
mq-db sql "INSERT INTO notes VALUES ('1', 'Hello world')" --db store.mq-db

# Inspect
mq-db sql "SHOW TABLES" --db store.mq-db
mq-db sql "DESC notes"  --db store.mq-db

# Drop
mq-db sql "DROP TABLE notes" --db store.mq-db

mq queries

mq-db mq ".h1" --db store.mq-db
mq-db mq 'select(.code_lang == "rust")' --db store.mq-db
mq-db mq ".h1" --db store.mq-db --format markdown  # also: json, csv, tsv, html

Interactive REPL

mq-db repl --db store.mq-db --mode sql

mq-db  (.help for commands  .quit to exit)
mode: sql  (.mode mq | .mode sql)

sql> SELECT content FROM blocks WHERE block_type = 'heading' LIMIT 3;
┌──────────────────┐
│ content          │
├──────────────────┤
│ Overview         │
│ Architecture     │
│ Query Engine     │
└──────────────────┘
(3 rows)

sql> .mode mq
→ mq mode
mq> .h2
## Architecture
## Query Engine

HTTP server

mq-db serve --db store.mq-db              # listens on 127.0.0.1:7878
mq-db serve --db store.mq-db --port 8080  # custom port
mq-db serve --db store.mq-db --host 0.0.0.0 --port 8080

Three endpoints are available:

Method	Path	Body	Description
`GET`	`/health`	—	`{"status":"ok","documents":<n>}`
`POST`	`/sql`	`{"query":"SELECT …"}`	Execute a SQL query, returns JSON rows
`POST`	`/mq`	`{"code":".h1"}`	Evaluate an mq expression, returns `{"results":[…]}`

# Health check
curl http://127.0.0.1:7878/health

# SQL via HTTP
curl -s -X POST http://127.0.0.1:7878/sql \
  -H 'Content-Type: application/json' \
  -d '{"query":"SELECT block_type, count(*) FROM blocks GROUP BY block_type"}'

# mq via HTTP
curl -s -X POST http://127.0.0.1:7878/mq \
  -H 'Content-Type: application/json' \
  -d '{"code":".h1"}'

Structural linting

mq-db lint --db store.mq-db --depth 2

✗  1 violation  (H2 immediately followed by list)

  file                                      heading
  ────────────────────────────────────────  ──────────────────────────────
  docs/DESIGN.md                            "Quick Start"

Statistics

mq-db stats --db store.mq-db

  Documents  5
  Blocks     632

  Block types
  ────────────────────────────────────────────────────────
   ¶  paragraph    ████████████████████░░░░   241  (38%)
   #  heading      ████████░░░░░░░░░░░░░░░░    89  (14%)
  {}  code         ███████░░░░░░░░░░░░░░░░░    73  (12%)
   •  list         ██████░░░░░░░░░░░░░░░░░░    58   (9%)

  Code languages
  ────────────────────────────────────────────────────────
  {}  rust         ████████████████████████    41  (57%)
  {}  python       ██████████░░░░░░░░░░░░░░    18  (25%)
  {}  bash         ███████░░░░░░░░░░░░░░░░░    14  (19%)

Show document structure

mq-db show 0 --db store.mq-db

  docs/DESIGN.md
  title   Design Document
  blocks  142

  pre   post  type               content
  ────  ────  ────────────────   ──────────────────────────────────────────
     0   141  heading H1         Design Document
     2    55  heading H2         Architecture
     4    21  paragraph          The system is built on…
    22    37  heading H3           Query Engine
    24    36  code                   fn main() { … }

TUI

mq-db tui --db store.mq-db

 mq-db  SQL  Tab:switch  i:input  j/k:nav  d/u:scroll  q:quit
┌─ Documents ──────────┬─ SQL ────────────────────────────────────────────────┐
│ DESIGN.md            │ SELECT block_type, count(*) FROM blocks GROUP BY b_  │
│   142 blocks         ├─ Results ────────────────────────────────────────────┤
│ API.md               │ ┌─────────────┬──────────┐                           │
│   87 blocks  API     │ │ block_type  │ count(*) │                           │
│ README.md            │ ├─────────────┼──────────┤                           │
│   34 blocks          │ │ paragraph   │ 48       │                           │
└──────────────────────┴──────────────────────────────────────────────────────┘
 5 docs  632 blocks  3 rows

Keys:

Key	Action
`i`	Focus query input
`Esc`	Blur input
`Enter`	Run query
`Tab`	Toggle mq / SQL mode
`j` / `k`	Navigate document list
`d` / `u`	Scroll results down / up
`g` / `G`	Jump to top / bottom
`q` / `Ctrl+C`	Quit

Library API

use mq_db::{DocumentStore, SqlEngine, MqEngine, block::BlockType};

// ── Build in memory ──────────────────────────────────────────────────────────
let mut store = DocumentStore::new();
store.add_file("docs/DESIGN.md")?;
store.add_str("# Hello\n\n## Architecture\n\nDetails\n")?;

// Chainable query API — zone-map skip + interval scope + block predicates
let chunks = store.query()
    .documents(|doc| doc.zone_maps.heading_contents.contains("Architecture"))
    .under_heading("Architecture", Some(2))
    .filter(|b| matches!(b.block_type, BlockType::Paragraph | BlockType::Code))
    .blocks();

// SQL engine (custom sqlparser-based evaluator — no SQLite dependency)
let engine = SqlEngine::new(&store)?;
let out = engine.execute(
    "SELECT content FROM blocks WHERE block_type = 'heading' ORDER BY pre"
)?;
print!("{}", out.to_table());

// mq engine
let results = MqEngine::eval_store(".h1", &store)?;

// Structural lint
let violations = store.query().lint_heading_followed_by(2, &[BlockType::List]);

// ── Persist / load ───────────────────────────────────────────────────────────
store.save("store.mq-db")?;

// Full load — all blocks read into memory, indexes built on first SqlEngine use
let store = DocumentStore::load("store.mq-db")?;

// Lazy open — catalog only; call load_all_blocks() + load_all_indexes() before SQL
let mut store = DocumentStore::open("store.mq-db")?;
store.load_all_blocks()?;
store.load_all_indexes()?;

// Catalog-only — for metadata commands (list, stats) that don't need block data
let store = DocumentStore::load_catalog_only("store.mq-db")?;

SQL Reference

Virtual schema

SELECT id, path, title, tags FROM documents;

SELECT id, document_id, block_type, content, pre, post,
       depth, lang, properties FROM blocks;

Built-in functions

Function	Description
`under(pre, post, anc_pre, anc_post)`	O(1) interval ancestor check
`mq(program, content)`	Run an mq program against Markdown content
`json_extract(json, path)`	Extract a value from a JSON string
`count(*) / min / max / sum / avg`	Aggregate functions
`lower / upper / length / coalesce`	Scalar utilities

DDL statements

Statement	Description
`CREATE TABLE name AS SELECT …`	Create a custom table from a query result
`CREATE TABLE name (col TYPE, …)`	Create an empty custom table with explicit schema
`INSERT INTO name VALUES (…)`	Insert a row into a custom table
`DROP TABLE name`	Drop a custom table
`SHOW TABLES`	List all custom tables
`DESC name`	Show schema of a custom table

Example queries

-- All text/code under a specific section (RAG extraction)
SELECT b.block_type, b.content
FROM blocks b
WHERE under(b.pre, b.post,
  (SELECT pre FROM blocks WHERE block_type = 'heading' AND content = 'Architecture'),
  (SELECT post FROM blocks WHERE block_type = 'heading' AND content = 'Architecture'))
  AND b.block_type IN ('paragraph', 'code')
ORDER BY b.pre;

-- Extract H1 title from code block content via the mq() scalar function
SELECT mq('.h1 | to_text', content) AS title
FROM blocks
WHERE block_type = 'code' AND lang = 'markdown';

-- H2 headings immediately followed by a list (structural lint)
SELECT d.path, h.content AS heading
FROM blocks h
JOIN blocks nxt ON nxt.document_id = h.document_id AND nxt.pre = h.pre + 1
JOIN documents d ON d.id = h.document_id
WHERE h.block_type = 'heading' AND depth = 2 AND nxt.block_type = 'list';

-- Documents containing Python code
SELECT DISTINCT d.path
FROM documents d JOIN blocks b ON b.document_id = d.id
WHERE b.block_type = 'code' AND lang = 'python';

Architecture

Block model

Every Markdown element becomes a Block:

struct Block {
    id: u32,
    document_id: u32,
    block_type: BlockType,  // Heading, Paragraph, Code, List, …
    content: String,
    span: Option<Span>,     // line/column for editor sync
    pre: u32,               // interval index pre-order
    post: u32,              // interval index post-order
    properties: Properties, // row-polymorphic extra attributes
}

Block type	Properties
`Heading`	`{ "depth": 2, "slug": "architecture" }`
`Code`	`{ "lang": "rust", "meta": "no_run" }`
`List`	`{ "ordered": false, "level": 1, "checked": null }`
`Yaml` / `Toml`	parsed front-matter keys (`"title"`, `"tags"`, …)

Index layers

mq-db applies three complementary index layers, cheapest-first.

flowchart LR
    Q["SQL Query"] --> ZM["Layer 1\nZone Maps\n(document skip)"]
    ZM -->|"relevant docs"| II["Layer 2\nInterval Index\n(section scope)"]
    II -->|"candidate blocks"| SI["Layer 3\nSecondary Indexes\n(block lookup)"]
    SI -->|"BitmapIndex\nBTreeIndex\nHashIndex"| R["Result Rows"]
    ZM -->|"skip"| X1["✗ irrelevant docs"]
    SI -->|"no hint"| FS["Full Scan"]

Layer 1 — Zone Maps (document-level skip)

Built once per document and stored in the .mq-db file. Checked before any block is read:

Field	Skips documents where…
`heading_contents`	The requested heading text is absent
`code_languages`	The requested language tag is absent
`max_heading_depth`	The requested depth cannot exist
`tags`	The tag filter cannot match

Layer 2 — Interval Index (section hierarchy)

Heading hierarchy encoded as (pre, post) pairs via Pre-Post Order (Nested Set) traversal:

graph TD
    doc["# Doc\npre=0 · post=11"]
    secA["## Section A\npre=2 · post=7"]
    para1["Paragraph\npre=3 · post=4"]
    code1["Code\npre=5 · post=6"]
    secB["## Section B\npre=8 · post=11"]
    para2["Paragraph\npre=9 · post=10"]

    doc --> secA
    doc --> secB
    secA --> para1
    secA --> code1
    secB --> para2

A is_under B ↔ B.pre < A.pre AND A.post < B.post — O(1), no tree traversal.

Layer 3 — Secondary Indexes (block-level fast lookup)

Index	Column(s)	Structure	Complexity
`BitmapIndex`	`block_type`	Inverted list per type	O(1) key + O(k) iterate
`BTreeIndex`	`pre`, `post`	`BTreeMap`	O(log n) point, O(log n + k) range
`HashIndex`	`content`, `lang`, `depth`	`HashMap`	O(1) average

SQL predicate pushdown picks an IndexHint:

flowchart TD
    P["SQL WHERE predicate"]
    P -->|"block_type = '...'"| B["BitmapIndex"]
    P -->|"pre = N"| BT1["BTreeIndex (point)"]
    P -->|"pre BETWEEN N AND M"| BT2["BTreeIndex (range)"]
    P -->|"content = '...'"| H1["HashIndex"]
    P -->|"lang = '...'"| H2["HashIndex"]
    P -->|"depth = N"| H3["HashIndex"]
    P -->|"other"| FS["Full Scan"]

Storage format

Custom 8 KB page file:

graph TD
    P0["Page 0 — File Header\nmagic 0x4D514442 · version · page count"]
    P1["Page 1 — Catalog\ndoc_id → first_block_page · num_blocks · ZoneMaps"]
    P2["Page 2+ — Block Data\nlinked page chains · overflow pages"]

    P0 --> P1 --> P2

Writes are atomic: data goes to <path>.tmp then renamed to <path> on success.

License

MIT

Name		Name	Last commit message	Last commit date
Latest commit History 25 Commits
.github/workflows		.github/workflows
assets		assets
bin		bin
docs		docs
src		src
.gitignore		.gitignore
Cargo.lock		Cargo.lock
Cargo.toml		Cargo.toml
LICENSE		LICENSE
README.md		README.md

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mq-db

Features

Installation

Using the Installation Script (Recommended)

Using Cargo

From Source

Supported Platforms

CLI Usage

Index Markdown files

List indexed documents

SQL queries

DDL — custom in-memory tables

mq queries

Interactive REPL

HTTP server

Structural linting

Statistics

Show document structure

TUI

Library API

SQL Reference

Virtual schema

Built-in functions

DDL statements

Example queries

Architecture

Block model

Index layers

Layer 1 — Zone Maps (document-level skip)

Layer 2 — Interval Index (section hierarchy)

Layer 3 — Secondary Indexes (block-level fast lookup)

Storage format

License

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