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LoraDB Query Cookbook

A scenario-driven companion to the clause-by-clause Queries reference. Reach for this page when you know the question ("who are my mutual follows?", "which orders are late?") but aren't sure how to shape the Cypher. Where the reference answers "what does this clause do", the cookbook answers "how do I ask this question".

Each recipe names a real problem, states its assumed data model, gives a query, and explains why it works — then lists useful variations and related concepts. Recipes are grouped by domain: social, e-commerce, events, geospatial, vector retrieval. Every query is idiomatic LoraDB — no APOC, no CALL, no window functions — and when a SQL idiom doesn't translate, the recipe shows the Cypher-native shape.

On this page​

Social graph patterns​

Recipe: Friends of friends​

Problem​

"For user $id, list people they don't follow yet, but who are followed by somebody they do follow."

Assumed data model​

  • :User {id, handle}
  • (u:User)-[:FOLLOWS]->(v:User) — directed "u follows v"

Query​

MATCH (me:User {id: $id})-[:FOLLOWS]->(friend:User)-[:FOLLOWS]->(candidate:User)
WHERE candidate <> me
  AND NOT EXISTS { (me)-[:FOLLOWS]->(candidate) }
RETURN candidate.handle,
       count(*) AS shared_paths
ORDER BY shared_paths DESC
LIMIT 20

Explanation​

The two-hop pattern enumerates every (me, friend, candidate) triple. NOT EXISTS removes candidates me already follows; candidate <> me removes self-loops. count(*) becomes the number of mutual friends — a useful ranking signal.

Variations​

  • Also consider followers: reverse the last segment to (candidate)-[:FOLLOWS]->(friend).
  • Combine both directions with a UNION and dedup with collect(DISTINCT …).
  • Weight by recency of friend's follow using a :FOLLOWS {since} property — see the e-commerce co-purchase recipe.

Recipe: Mutual connections​

Problem​

"List pairs of users who follow each other."

Assumed data model​

  • :User
  • (a)-[:FOLLOWS]->(b) — directed

Query​

MATCH (a:User)-[:FOLLOWS]->(b:User)-[:FOLLOWS]->(a)
WHERE id(a) < id(b)
RETURN a.handle, b.handle

Explanation​

The pattern reads "a follows b and b follows a" — a 2-cycle. The id(a) < id(b) predicate keeps one row per unordered pair; without it you'd get both (alice, bob) and (bob, alice).

Variations​

  • Add a property filter: only mutuals where both accounts are active — add WHERE a.active AND b.active.
  • Rank by "oldest mutuals first" by collecting the relationship: MATCH (a)-[r1:FOLLOWS]->(b)-[r2:FOLLOWS]->(a) and order by min(r1.since, r2.since) — see ORDER BY.

Recipe: Recommendations via second-degree connections​

Problem​

"Recommend accounts for $id to follow, ranked by how many of their current follows already follow that account."

Assumed data model​

  • :User
  • (u)-[:FOLLOWS]->(v)

Query​

MATCH (me:User {id: $id})-[:FOLLOWS]->(:User)-[:FOLLOWS]->(rec:User)
WHERE rec <> me
  AND NOT EXISTS { (me)-[:FOLLOWS]->(rec) }
RETURN rec.handle,
       count(*) AS score,
       collect(DISTINCT rec.country)[..3] AS sample_countries
ORDER BY score DESC
LIMIT 10

Explanation​

Similar to friends-of-friends but projects a richer result — the count becomes a recommendation score, and we collect a diverse sample of metadata. [..3] slices the collected list to the first three entries — a list slice.

Variations​

  • Add a CASE-based boost for accounts with a verified badge: count(CASE WHEN rec.verified THEN 1 END) * 2 + count(*).
  • Expand to 3-hop with [:FOLLOWS*2..3] — bound it to avoid run-away — see Paths → variable-length.

Recipe: Influence score (weighted walk)​

Problem​

"For each user, estimate an influence score based on how many followers reach them within two hops."

Assumed data model​

  • :User
  • (follower)-[:FOLLOWS]->(followee) — standard directed follow

Query​

MATCH (u:User)
OPTIONAL MATCH (u)<-[:FOLLOWS*1..2]-(reacher:User)
RETURN u.handle,
       count(DISTINCT reacher) AS reach
ORDER BY reach DESC
LIMIT 20

Explanation​

OPTIONAL MATCH preserves users with zero reach. count(DISTINCT reacher) avoids double-counting any user reached through multiple paths. Bounded at two hops to stay tractable.

Variations​

  • Replace reacher with count(DISTINCT length(p)) paths of different lengths to reveal reach-at-each-distance.
  • Combine with :FOLLOWS {since} weights: sum(exp(-duration.inDays(r.since, datetime()) * 0.02)).

E-commerce patterns​

Recipe: Top N products by revenue​

Problem​

"The ten products with the highest paid-order revenue this month."

Assumed data model​

  • :Product {id, name, price}
  • :Order {id, placed_at, status}
  • (o)-[:CONTAINS {quantity}]->(p)

Query​

MATCH (o:Order)-[c:CONTAINS]->(p:Product)
WHERE o.status = 'paid'
  AND o.placed_at >= date.truncate('month', date())
RETURN p.name,
       sum(c.quantity * p.price) AS revenue,
       sum(c.quantity)           AS units,
       count(DISTINCT o)         AS orders
ORDER BY revenue DESC
LIMIT 10

Explanation​

Joins orders and products through the :CONTAINS edge, filters to paid orders in the current month, then aggregates revenue per product. count(DISTINCT o) captures orders (an order can contain many items), distinct from the total units sold.

Variations​

  • Top-N per category: group by p.category as well and then pick-first within each using collect(…)[..1].
  • Year-to-date: replace the date filter with o.placed_at >= date.truncate('year', date()).

Recipe: Co-purchase patterns​

Problem​

"Which products are frequently bought together with $sku?"

Assumed data model​

  • :Product {sku}
  • :Order
  • (o)-[:CONTAINS]->(p)

Query​

MATCH (anchor:Product {sku: $sku})<-[:CONTAINS]-(:Order)-[:CONTAINS]->(other:Product)
WHERE other <> anchor
RETURN other.sku,
       count(*) AS co_orders
ORDER BY co_orders DESC
LIMIT 20

Explanation​

Traverses orders that contain the anchor product and jumps to other products in the same order. count(*) is the number of orders in which the co-occurrence happened.

Variations​

  • Only ship-completed orders: add WHERE o.status = 'shipped' after binding (o:Order).
  • Lift score over per-product baseline: count(*) * 1.0 / ((MATCH (:Order)-[:CONTAINS]->(anchor)…)) — two stages combined via WITH — see Aggregation → pipeline aggregation.

Recipe: Repeat buyers​

Problem​

"Users who placed more than one paid order."

Assumed data model​

  • :User
  • :Order {status}
  • (u)-[:PLACED]->(o)

Query​

MATCH (u:User)-[:PLACED]->(o:Order {status: 'paid'})
WITH u, count(o) AS orders
WHERE orders > 1
RETURN u.email,
       orders
ORDER BY orders DESC

Explanation​

Classic HAVING-style pipeline: aggregate first, then filter the aggregated column. Cypher has no HAVING keyword — pipe through WITH instead.

Variations​

  • Lifetime value: replace count(o) with sum(o.amount).
  • Last-purchase recency: add max(o.placed_at) AS last and filter on that.

Recipe: Cart abandonment​

Problem​

"Users with an open cart containing more than $n items, but no order placed in the last 30 days."

Assumed data model​

  • :User
  • :Cart {status}, :Item
  • (u)-[:HAS_CART]->(c), (c)-[:CONTAINS]->(:Item), (u)-[:PLACED]->(:Order)

Query​

MATCH (u:User)-[:HAS_CART]->(c:Cart {status: 'open'})-[:CONTAINS]->(i:Item)
WITH u, c, count(i) AS items
WHERE items > $n
  AND NOT EXISTS {
    (u)-[:PLACED]->(o:Order)
    WHERE o.placed_at >= datetime() - duration('P30D')
  }
RETURN u.email, c.id, items
ORDER BY items DESC

Explanation​

The NOT EXISTS { } sub-pattern is an anti-join — keeps users without any recent order. The surrounding pipeline filters open carts above the threshold size.

Variations​

  • Add recency of cart update: AND c.updated_at >= datetime() - duration('P7D') for "stale but not abandoned".
  • Compute total cart value: sum(i.price * i.quantity) AS total.

Event / time-based patterns​

Recipe: Attendees per event​

Problem​

"Total and unique attendees for each upcoming event, plus a flag for whether the event is sold out."

Assumed data model​

  • :Event {id, starts_at, capacity}
  • :User
  • (u)-[:RSVP {status}]->(e)

Query​

MATCH (e:Event)
WHERE e.starts_at >= datetime()
OPTIONAL MATCH (u:User)-[r:RSVP {status: 'yes'}]->(e)
WITH e, count(u) AS going
RETURN e.id,
       e.starts_at,
       going,
       e.capacity,
       CASE
         WHEN going >= e.capacity THEN 'sold_out'
         WHEN going >= e.capacity * 0.8 THEN 'filling'
         ELSE 'open'
       END AS status
ORDER BY e.starts_at

Explanation​

OPTIONAL MATCH ensures events with zero RSVPs still appear. CASE computes a tiered status per event.

Variations​

  • Break out by ticket tier: collect(DISTINCT r.tier) AS tiers.
  • Include "maybe" RSVPs separately: count(CASE WHEN r.status = 'maybe' THEN 1 END) AS maybes.

Recipe: Events in a rolling window​

Problem​

"All events between now and $horizon_days days in the future, with their host."

Assumed data model​

  • :Event {starts_at}
  • :User (host)
  • (u)-[:HOSTS]->(e)

Query​

MATCH (host:User)-[:HOSTS]->(e:Event)
WHERE e.starts_at >= datetime()
  AND e.starts_at <  datetime() + duration({days: $horizon_days})
RETURN e.id,
       e.starts_at,
       host.handle
ORDER BY e.starts_at

Explanation​

duration({days: $horizon_days}) accepts a bound integer — duration('P7D') only works with a literal string. Use the map form whenever the window size is dynamic.

Variations​

  • Hour-bucket count to drive a chart: datetime.truncate('hour', e.starts_at) grouped with count(*) — see Temporal → bucketing.
  • Timezone-specific: store starts_at as DateTime (UTC-offset aware) — see Temporal types.

Recipe: Overlapping attendance​

Problem​

"For each pair of users who attended at least $n common events this year, list the events they shared."

Assumed data model​

  • :User, :Event
  • (u)-[:ATTENDED]->(e) with e.at: DateTime

Query​

MATCH (a:User)-[:ATTENDED]->(e:Event)<-[:ATTENDED]-(b:User)
WHERE id(a) < id(b)
  AND e.at >= date.truncate('year', date())
WITH a, b, collect(DISTINCT e.id) AS shared
WHERE size(shared) >= $n
RETURN a.handle, b.handle, shared, size(shared) AS n_shared
ORDER BY n_shared DESC

Explanation​

The pattern generates all (a, e, b) triples for attendees of the same event. id(a) < id(b) keeps one row per unordered pair. collect(DISTINCT e.id) deduplicates events (an attendee can't attend the same event twice but the pattern could still double-count in more complex schemas).

Variations​

  • Use count(DISTINCT e) instead of size(collect(…)) for a cheaper pairwise score when you don't need the event ids.
  • Weight events by e.importance.

Recipe: Cohort retention​

Problem​

"For each signup-month cohort, what fraction of users logged in during the last 30 days?"

Assumed data model​

  • :User {id, created}
  • :Login {at}
  • (u)-[:LOGGED_IN]->(l:Login)

Query​

MATCH (u:User)
WITH date.truncate('month', u.created) AS cohort, u
OPTIONAL MATCH (u)-[:LOGGED_IN]->(l:Login)
WHERE l.at >= datetime() - duration('P30D')
RETURN cohort,
       count(DISTINCT u)                                   AS total,
       count(DISTINCT CASE WHEN l IS NOT NULL THEN u END)  AS active_30d,
       toFloat(count(DISTINCT CASE WHEN l IS NOT NULL THEN u END))
         / count(DISTINCT u)                               AS retention
ORDER BY cohort

Explanation​

OPTIONAL MATCH preserves cohort members who never logged in. Counting DISTINCT u gives cohort size; the conditional CASE inside count(DISTINCT …) gives the active subset. The division yields retention between 0 and 1.

Variations​

  • Slice by acquisition channel: add WITH cohort, u.channel AS channel, u and include channel in the RETURN.
  • Wider windows: change P30D to P90D / P365D.

Geospatial patterns​

Recipe: N nearest places​

Problem​

"Ten nearest venues to $here, with distance in metres."

Assumed data model​

  • :Venue {id, name, location: Point} — WGS-84 2D preferred

Query​

MATCH (v:Venue)
WITH v, distance(v.location, $here) AS metres
WHERE metres IS NOT NULL            -- guard cross-SRID
RETURN v.name, metres
ORDER BY metres
LIMIT 10

Explanation​

distance on same-SRID WGS-84 points returns metres. The null guard catches cases where some venues were stored with a different SRID — cross-SRID distance returns null.

Variations​

  • Cluster by kilometre ring: toInteger(metres / 1000) AS km grouped with count(*).
  • Include only open venues: WHERE v.status = 'open' before the distance computation.

Recipe: Region / bounding-box filter​

Problem​

"Every city between latitudes $s..$n and longitudes $w..$e."

Assumed data model​

  • :City {name, location} — WGS-84 2D

Query​

MATCH (c:City)
WHERE c.location.latitude  >= $s AND c.location.latitude  <= $n
  AND c.location.longitude >= $w AND c.location.longitude <= $e
RETURN c.name, c.location.latitude AS lat, c.location.longitude AS lon
ORDER BY lat

Explanation​

LoraDB has no point.withinBBox() — compose the four bounds explicitly with >= / <=. BETWEEN is also unsupported. See Limitations.

Variations​

  • Combine with category filter: WHERE c.country = $country AND ….
  • Return area-approximated stats with count(*) grouped by rounded coordinates — see Cluster by rounded coordinates.

Recipe: Closest-per-category​

Problem​

"Nearest shop of each category to $here."

Assumed data model​

  • :Shop {category, location} — WGS-84 2D

Query​

MATCH (s:Shop)
WITH s.category AS category, s, distance(s.location, $here) AS metres
ORDER BY metres ASC
WITH category, collect({s: s, metres: metres})[0] AS nearest
RETURN category,
       nearest.s.name AS name,
       nearest.metres AS metres
ORDER BY metres

Explanation​

Order by distance first, then collect per category. The first collected element is the closest. collect(…)[0] is the group-level "pick one" idiom — LoraDB has no window functions.

Variations​

  • Pick the farthest in each category: sort DESC.
  • Top-3 per category: collect(…)[..3] and then UNWIND to one row per shop.

Recipe: Join on proximity​

Problem​

"Find all pairs of sensors within 500 metres of each other."

Assumed data model​

  • :Sensor {id, location} — WGS-84 2D

Query​

MATCH (a:Sensor), (b:Sensor)
WHERE id(a) < id(b)
  AND distance(a.location, b.location) < 500
RETURN a.id, b.id, distance(a.location, b.location) AS metres
ORDER BY metres

Explanation​

The Cartesian join between sensors is expensive — use a label scope to keep it tight. The id(a) < id(b) predicate removes symmetric pair duplicates.

Variations​

  • Constrain by network / region first (WHERE a.region = b.region) to shrink the cartesian product dramatically.
  • Store a Cartesian point instead for small domains (floor plans, game maps) — distance is then an O(1) square root.

Vector-retrieval patterns​

Recipe: Top-k by similarity​

Problem​

"Return the ten documents most similar to $query, exhaustive scan."

Assumed data model​

  • :Doc {id, title, embedding} — embedding is a VECTOR<FLOAT32> of fixed dimension (e.g. 384 for a small sentence-transformer).

Query​

MATCH (d:Doc)
RETURN d.id AS id, d.title AS title
ORDER BY vector.similarity.cosine(d.embedding, $query) DESC
LIMIT 10

Pass $query either as a tagged vector (vector([...], 384, FLOAT32) on the host) or as a plain numeric list — both are accepted by the similarity function. See Vectors → Passing vectors as parameters.

Explanation​

Vector indexes are not implemented yet, so every matched node is scored linearly. Keep the MATCH as narrow as possible (label, property filter) to shrink the candidate set before similarity runs.

Variations​

  • Score in a WITH stage if the score is reused downstream: WITH d, vector.similarity.cosine(d.embedding, $query) AS score.
  • Swap the metric for Euclidean-bounded similarity (vector.similarity.euclidean) or a signed distance (vector_distance(d.embedding, $query, EUCLIDEAN), then ORDER BY … ASC).

Recipe: Graph-filtered retrieval​

Problem​

"Return the five documents most similar to $query, but only those that mention an entity of a given type — and include the matched entity names in the result."

Assumed data model​

  • :Doc {id, title, embedding} with a VECTOR embedding.
  • (:Doc)-[:MENTIONS]->(:Entity {name, type}).

Query​

MATCH (d:Doc)
WITH d, vector.similarity.cosine(d.embedding, $query) AS score
MATCH (d)-[:MENTIONS]->(e:Entity)
WHERE e.type = $entity_type
RETURN d.id, d.title, score, collect(e.name) AS entities
ORDER BY score DESC
LIMIT 5

Explanation​

Similarity supplies candidates; the graph explains and constrains them. The score is captured once in the first WITH, then the pipeline walks MENTIONS edges for filtering and returns the entity list alongside the ranking. This is the shape that motivated putting VECTOR next to the graph.

Variations​

  • Filter before scoring if the entity constraint is selective — move the MATCH (d)-[:MENTIONS]->(e:Entity {type: $entity_type}) above the similarity WITH so similarity only scores documents that already passed the entity filter.
  • Rerank by recency as a tie-breaker: ORDER BY score DESC, d.updated_at DESC.

Backup and restore​

LoraDB's snapshot API lets you persist the full graph to a single file and restore it later. It's a point-in-time dump — atomic on rename and still useful when you also enable WAL-backed recovery. These recipes cover the common snapshot and checkpoint shapes.

Recipe: Periodic snapshot from host code​

Problem​

"Persist the live graph every N minutes from the same process that owns the Database handle."

Assumed setup​

Code (Rust)​

use std::time::Duration;
use std::sync::Arc;
use lora_database::Database;

fn snapshot_loop(db: Arc<Database>, path: &'static str) {
    std::thread::spawn(move || loop {
        std::thread::sleep(Duration::from_secs(300));
        match db.save_snapshot_to(path) {
            Ok(meta) => tracing::info!(
                nodes = meta.node_count,
                rels  = meta.relationship_count,
                "snapshot saved"
            ),
            Err(e) => tracing::error!(error = %e, "snapshot failed"),
        }
    });
}

Explanation​

  • save_snapshot_to writes to <path>.tmp, fsyncs, and renames over the target — a crashed save never leaves a half-written file at <path>.
  • The call serialises against every query on the handle. The mutex is held for the serialize step (O(n + r) in nodes and relationships). Pick an interval larger than the measured save wall-time so successive saves don't stack.
  • You can safely overwrite the same path on every tick. For versioned backups, rotate the filename (graph-2026-04-24.bin) and garbage-collect outside the process.

Variations​

  • Rotating filenames. Append a date stamp and prune on a cron.
  • HTTP from a cron job. If the server runs with --snapshot-path, call POST /admin/snapshot/save from an external cron instead of a thread inside the process. See HTTP API → Admin endpoints.
  • Python / Node / WASM / Go / Ruby. Same shape — see each quickstart's Persisting your graph section: Rust, Python, Node, WASM, Go, Ruby.

Recipe: Boot from snapshot, save on shutdown (server setup)​

Problem​

"Self-hosted lora-server should load state at start-up and persist it on graceful shutdown."

Assumed setup​

  • A host running lora-server as a long-lived process (systemd, Docker, plain nohup, …).
  • A writable path for the snapshot file.

Configuration​

# start-up — restore from, and default-save to, the same file
lora-server \
  --host 127.0.0.1 --port 4747 \
  --snapshot-path /var/lib/lora/db.bin \
  --restore-from  /var/lib/lora/db.bin

--restore-from at boot: missing file is fine (empty graph, logged); malformed file is fatal.

Save on shutdown (systemd sketch)​

# /etc/systemd/system/lora-server.service
[Service]
ExecStart=/usr/local/bin/lora-server \
  --host 127.0.0.1 --port 4747 \
  --snapshot-path /var/lib/lora/db.bin \
  --restore-from  /var/lib/lora/db.bin
ExecStop=/usr/bin/curl -sX POST http://127.0.0.1:4747/admin/snapshot/save
TimeoutStopSec=30

The ExecStop call saves the current state before the process is killed. TimeoutStopSec needs to comfortably cover your measured save duration.

Explanation​

  • The admin endpoints are opt-in — they're mounted only because --snapshot-path is set. On any other host they return 404.
  • The admin surface has no authentication, so the bind address must be privileged (here: 127.0.0.1 only). See HTTP API → Admin endpoints (opt-in) for the security warning.
  • The save runs as the server UID, which must have write access to the target path and its parent directory.

Variations​

  • Scheduled cron-driven saves. Combine the boot-from-snapshot setup above with a systemd .timer unit or an ordinary cron that curls POST /admin/snapshot/save every N minutes. The endpoint returns a SnapshotMeta you can log for observability.
  • Immutable seed + writable runtime. Pass --restore-from /var/lib/lora/seed.bin and --snapshot-path /var/lib/lora/runtime.bin to boot from a shared seed and save to a host-local file.

Recipe: WAL-backed server with explicit checkpoints​

Problem​

"Recover committed writes after a crash, but keep replay time bounded with operator-driven checkpoints."

Assumed setup​

  • lora-server owns a writable WAL directory.
  • A writable snapshot path where checkpoints should land.
  • Admin endpoints are reachable only through trusted local transport or authenticated ingress.

Configuration​

lora-server \
  --host 127.0.0.1 --port 4747 \
  --wal-dir /var/lib/lora/wal \
  --snapshot-path /var/lib/lora/db.bin \
  --restore-from /var/lib/lora/db.bin

Checkpoint cadence​

# Inspect the WAL before deciding whether to checkpoint.
curl -sX POST http://127.0.0.1:4747/admin/wal/status

# Write a checkpoint snapshot to --snapshot-path and truncate safe history.
curl -sX POST http://127.0.0.1:4747/admin/checkpoint

If you run WAL-only without --snapshot-path, pass the checkpoint target explicitly:

curl -sX POST http://127.0.0.1:4747/admin/checkpoint \
  -H 'content-type: application/json' \
  -d '{"path":"/var/lib/lora/checkpoint.bin"}'

Explanation​

  • Normal writes are logged to /var/lib/lora/wal. Restarting with the same --wal-dir replays committed records automatically.
  • POST /admin/checkpoint writes a snapshot stamped with walLsn, appends a checkpoint marker, then drops sealed WAL segments that are safe to remove.
  • --restore-from and --snapshot-path are independent. They can be the same file for a simple single-host setup, or different files for an immutable seed plus writable runtime checkpoint.
  • There is no automatic checkpoint loop yet. Trigger the endpoint from a systemd timer, cron, deployment hook, or host process after you measure acceptable replay time.

See the canonical Snapshots guide for the file format and every binding's save / load API, and WAL and checkpoints for recovery, sync modes, and admin semantics.

See also​