fmql 0.2.0

A schemaless query engine and editor for directories of frontmatter files.

fmql — FrontMatter Utilities

A schemaless query engine and editor for directories of frontmatter (markdown + YAML) files.

Point it at any directory of markdown/YAML files. Query with filters, traversal, aggregation, and graph patterns. Edit properties across single files or entire result sets. No configuration, no schema, no setup.

Installation

pip install fmql

From source:

git clone https://github.com/buyuk-dev/fmql.git
cd fmql
uv sync                    # or: pip install -e '.[dev]'

Requires Python 3.11+.

Quickstart

CLI:

fmql query ./project 'status = "active" AND priority > 2'
fmql query ./project 'due_date < today' --format json

Python:

from fmql import Workspace, Query

ws = Workspace("./project")
q = Query(ws).where(status="active", priority__gt=2)
for packet in q:
    print(packet.id)

Features

• Filter DSL — SQL-ish string queries, case-insensitive keywords, typed comparisons, date literals.
• Python kwargs API — Django-style field__op=value with a full operator registry.
• Edit operations — set, remove, rename, append, toggle on single files or bulk result sets, with diff preview and confirmation.
• Format-preserving YAML — round-trip via ruamel.yaml; edits preserve comments, key order, and quoting of untouched fields.
• Traversal — follow() resolves reference fields (paths, UUIDs, slugs) forward or reverse, bounded or transitive.
• Aggregation — group_by(...).aggregate(Count, Sum, Avg, Min, Max).
• Describe — workspace introspection: observed fields, types, distinct-value samples.
• Cypher subset — graph patterns for dependency chains, cycle detection, multi-hop traversal.
• Pluggable search — third-party backends register via Python entry points (fmql.search_index). Ships with a grep scan backend; third-party packages can add indexed backends (fmql-fts, fmql-semantic, …).

CLI reference

Command	Purpose	Example
query	Run a filter query against a workspace	fmql query ./project 'status = "active"'
set	Set frontmatter fields	fmql set ./tasks/task-42.md status=done priority=1
remove	Remove frontmatter fields	fmql remove ./tasks/task-42.md temp_notes
rename	Rename frontmatter fields	fmql rename ./tasks/task-42.md assignee=assigned_to
append	Append to list-valued fields	fmql append ./tasks/task-42.md tags=urgent
toggle	Toggle boolean fields	fmql toggle ./tasks/task-42.md flagged
describe	Workspace introspection	fmql describe ./project
cypher	Graph pattern query (Cypher subset)	fmql cypher ./project 'MATCH (a)-[:blocked_by]->(b) RETURN a, b'
search	Run a search backend against a workspace/index	fmql search 'alice' --workspace ./project
index	Build an index for an indexed backend	fmql index ./project --backend semantic --out ./project/.fmql/semantic
list-backends	Enumerate discovered search backends	fmql list-backends

Common flags:

• --format {paths,json,rows} — output format (default: paths for query, rows for cypher).
• --follow FIELD, --depth N|'*', --direction {forward,reverse} — traversal on query.
• --resolver {path,uuid,slug} — reference resolution strategy for traversal/Cypher.
• --search QUERY, --index NAME, --index-location LOCATION — pluggable search stage (backend default: grep).
• --dry-run, --yes — preview or auto-confirm for edit commands.
• --workspace ROOT — explicit workspace root when piping paths into edit commands.

Run fmql <command> --help for the full flag list on any command.

Query syntax

Filter DSL (query command and qlang)

Logical operators (case-insensitive):

AND   OR   NOT   ( ... )

Comparisons:

= != > >= < <=
CONTAINS      — substring match on strings/lists
MATCHES       — regex match on strings
IN [v1, v2]   — membership test
IS EMPTY      — field missing or empty
IS NOT EMPTY
IS NULL

Values: quoted strings ("active"), numbers (42, 3.14), booleans (true, false), ISO dates (2026-05-01), and date sentinels:

today          now
yesterday      tomorrow
today-7d       now+1h        today+30d

Examples:

fmql query ./project 'status = "active" AND priority > 2'
fmql query ./project 'due_date < today AND status != "done"'
fmql query ./project 'tags CONTAINS "urgent" OR priority >= 3'
fmql query ./project 'status IN ["todo", "in_progress"]'
fmql query ./project 'NOT (assigned_to IS EMPTY)'
fmql query ./project 'title MATCHES "^\\[WIP\\]"'

Python kwargs API

field__op=value — everything before the final __ is the field, everything after is the operator. No __ means eq.

Operator	Matches when field value…
eq (default)	equals the expected value (booleans stay distinct from ints)
ne / not	is present and does not equal
gt, gte, lt, lte	is a comparable type and ordered accordingly
in	is in the given list/tuple/set
not_in	is present and not in the list
contains	is a string containing the substring, or a list containing the value
icontains	same as contains, case-insensitive for strings
startswith, endswith	string prefix / suffix match
matches	matches the given regex
exists	field is present (any value, truthy flag)
not_empty	field is present and not empty / zero-length
is_null	field value is explicitly null
type	field value's type name equals the expected (int, str, list, date, …)

Type-honest: non-comparable values are silently excluded, not coerced. priority > 2 matches packets where priority is an int > 2; packets where it's a string or missing are just not in the result.

from fmql import Query, Workspace

ws = Workspace("./project")
Query(ws).where(status="active", priority__gt=2)
Query(ws).where(tags__contains="urgent")
Query(ws).where(status__in=["todo", "in_progress"])
Query(ws).where(assigned_to__not_empty=True)
Query(ws).where(title__matches=r"^\[WIP\]")

Cypher subset (cypher command)

MATCH (a)-[:field]->(b)                 # single hop
MATCH (a)-[:field*]->(b)                # transitive
MATCH (a)-[:field*1..5]->(b)            # bounded depth
MATCH (a)-[:blocked_by*]->(a)           # cycle detection
WHERE a.status = "active" AND b.priority > 2
RETURN a
RETURN a, b
RETURN a.title
RETURN count(a)

Node labels parse but are ignored (schemaless). The WHERE clause uses the same operators as the filter DSL.

fmql cypher ./project 'MATCH (a)-[:blocked_by*]->(a) RETURN a'
fmql cypher ./project 'MATCH (a)-[:belongs_to]->(e) WHERE e.type = "epic" RETURN a, e'

Traversal & resolvers

--follow FIELD turns the result set into the starting seeds for a graph walk along that field. --depth N bounds the walk (use * for transitive). --direction reverse walks incoming edges instead of outgoing.

# Direct dependencies of one task
fmql query ./project 'uuid = "task-42"' --follow blocked_by --depth 1

# Full transitive dependency chain
fmql query ./project 'uuid = "task-42"' --follow blocked_by --depth '*'

# What does task-42 unblock? (reverse edge)
fmql query ./project 'uuid = "task-42"' --follow blocked_by --direction reverse

References in frontmatter fields are resolved by the selected resolver:

• path (default) — relative filesystem paths, e.g. blocked_by: ../tasks/task-41.md.
• uuid — matches a uuid frontmatter field on other packets.
• slug — matches a slug frontmatter field on other packets.

Pass --resolver uuid / --resolver slug to switch. Unresolvable references are dropped silently.

Aggregation & describe

Group-and-aggregate returns one row per group:

from fmql import Query, Workspace
from fmql import Count, Sum, Avg

ws = Workspace("./project")
(
    Query(ws)
    .where(type="task", in_sprint="sprint-3")
    .group_by("status")
    .aggregate(count=Count(), points=Sum("points"))
)

describe summarises a workspace — fields observed, types seen per field, and a sample of distinct values:

fmql describe ./project
fmql describe ./project --format json --top 10

Editing & safety

Every edit is previewable, confirmable, and preserves comments, key order, quoting, and body bytes.

# Single file
fmql set ./project/tasks/task-42.md status=escalated priority=1
fmql remove ./project/tasks/task-42.md temp_notes
fmql rename ./project/tasks/task-42.md assignee=assigned_to
fmql append ./project/tasks/task-42.md tags=urgent
fmql toggle ./project/tasks/task-42.md flagged

# Bulk: pipe query results into edits
fmql query ./project 'status != "done" AND due_date < today' \
  | fmql set status=escalated --workspace ./project --yes

# Preview without writing
fmql set ./project/tasks/task-42.md status=done --dry-run

Python equivalent:

from fmql import Workspace, Query

ws = Workspace("./project")
plan = Query(ws).where(status="active").set(status="reviewed")
print(plan.dry_run())       # unified diff
plan.apply(confirm=False)   # write

Value coercion from CLI strings: true/false → bool; integers and floats parsed as numbers; ISO dates (2026-05-01) parsed as dates; null → None. Quote to force string: label='"123"'.

Safety model. Bulk edits print a unified diff and prompt before writing. --dry-run shows the diff without writing; --yes skips the prompt. When stdin is piped (fmql query ... | fmql set ...), the prompt reopens /dev/tty — on systems without a tty (CI, containers), pass --yes.

Formatting. fmql re-emits edited YAML with 2-space mapping indent and 4-space sequence offset (ruamel defaults with explicit offset). Files that don't conform can still be parsed; only edited files are re-emitted, and untouched keys round-trip byte-for-byte.

Writing a search backend

Third-party packages can register search backends via the fmql.search_index entry-point group. Core makes no assumptions about what an index is or where it lives — the backend decides.

Pick one of two protocols:

• ScanSearch — scans the workspace at query time. No build step.
• IndexedSearch — builds a persistent index that fmql index rebuilds and fmql search --index LOCATION queries.

Minimal scan backend:

from fmql.search import BackendInfo, ScanSearch, SearchHit

class MyBackend:
    name = "mine"

    def query(self, text, workspace, *, k=10, options=None):
        hits = []
        for pid, packet in workspace.packets.items():
            if text.lower() in packet.body.lower():
                hits.append(SearchHit(packet_id=pid, score=1.0))
                if len(hits) >= k:
                    break
        return hits

    def info(self):
        return BackendInfo(name=self.name, version="0.1.0", kind="scan")

Register in your pyproject.toml:

[project.entry-points."fmql.search_index"]
mine = "my_package:MyBackend"

After pip install, fmql list-backends will pick it up and fmql search "text" --backend mine --workspace ./ws will invoke it. For indexed backends, also implement parse_location, default_location, and build; fmql.search.conformance exposes reusable assertions you can drive from your own tests. See docs/plugins_arch.md for the full protocol.

Development

uv sync --extra dev
make test    # run pytest
make lint    # ruff + black --check
make cov     # pytest with coverage (fails under 84%)
make format  # black

Status

v0.1.0 — first public release. All five design phases shipped: read path (filters, qlang, Python API), edit path (surgical YAML edits + bulk pipe), relationships & traversal (follow + resolvers), aggregation & describe, and the Cypher subset with pluggable search.

Links

• Design document — rationale, comparisons, target surface.
• LICENSE — MIT.
• GitHub — source, issues, releases.