neo4j-query-tuning-skill

EXPLAIN MATCH (p:Person {email: $email}) RETURN p.name
PROFILE MATCH (p:Person {email: $email}) RETURN p.name

curl -X POST https://<host>/db/<db>/query/v2 \
  -u <user>:<pass> -H "Content-Type: application/json" \
  -d '{"statement": "EXPLAIN MATCH (p:Person {email: $email}) RETURN p.name", "parameters": {"email": "a@b.com"}}'

EXPLAIN <query>

SHOW INDEXES YIELD name, type, labelsOrTypes, properties, state
WHERE state = 'ONLINE'

// RANGE index for equality/range predicates:
CREATE INDEX person_email IF NOT EXISTS FOR (n:Person) ON (n.email)
// TEXT index for CONTAINS/ENDS WITH:
CREATE TEXT INDEX person_bio IF NOT EXISTS FOR (n:Person) ON (n.bio)
// Composite for multi-property lookup:
CREATE INDEX order_status_date IF NOT EXISTS FOR (n:Order) ON (n.status, n.createdAt)

PROFILE <query>

CALL db.prepareForReplanning()
// or resample a specific index:
CALL db.resampleIndex("person_email")
// or resample all outdated:
CALL db.resampleOutdatedIndexes()

// Force index hint when planner ignores it:
MATCH (p:Person {email: $email})
USING INDEX p:Person(email)
RETURN p.name
// Force label scan (sometimes faster for high selectivity):
MATCH (p:Person {email: $email})
USING SCAN p:Person
RETURN p.name

// Force join at specific node:
MATCH (a:Author)-[:WROTE]->(b:Book)-[:IN_CATEGORY]->(c:Category {name: $cat})
USING JOIN ON b
RETURN a.name, b.title

// Bad (Cartesian product):
MATCH (a:Author {id: $aid})
MATCH (b:Book  {id: $bid})
RETURN a.name, b.title

// Good (explicit join or WITH):
MATCH (a:Author {id: $aid})-[:WROTE]->(b:Book {id: $bid})
RETURN a.name, b.title
// Or: WITH between them to reset planning context

CYPHER 25
MATCH (p:Person) WHERE p.score > 100
CALL (p) { SET p.tier = 'gold' } IN TRANSACTIONS OF 1000 ROWS

// Needs TEXT index (RANGE does NOT support these):
CREATE TEXT INDEX person_bio IF NOT EXISTS FOR (n:Person) ON (n.bio)
MATCH (p:Person) WHERE p.bio CONTAINS $keyword RETURN p.name

// Bad: LIMIT after expensive join
MATCH (a:Author)-[:WROTE]->(b:Book)-[:REVIEWED_BY]->(r:Review)
RETURN a.name, b.title, r.text LIMIT 10

// Good: anchor limit before fan-out
MATCH (a:Author)-[:WROTE]->(b:Book)
WITH a, b LIMIT 10
MATCH (b)-[:REVIEWED_BY]->(r:Review)
RETURN a.name, b.title, r.text

// Force parallel for large aggregation:
CYPHER 25 runtime=parallel
MATCH (n:Transaction) WHERE n.amount > 1000
RETURN n.currency, count(*), sum(n.amount)

// Live queries + resource usage:
SHOW QUERIES YIELD query, queryId, elapsedTimeMillis, allocatedBytes, status, username

// Running transactions:
SHOW TRANSACTIONS YIELD transactionId, currentQuery, currentQueryProgress, elapsedTime, status, username, cpuTime, activeLockCount  // currentQueryProgress added [2026.03]

// Kill a specific transaction:
TERMINATE TRANSACTION $transactionId

// Kill a query:
TERMINATE QUERY $queryId

// Graph count stats (node/rel counts by label/type — feed into planner):
CALL db.stats.retrieve('GRAPH COUNTS') YIELD section, data RETURN section, data

// Token stats (label/property/rel-type IDs):
CALL db.stats.retrieve('TOKENS') YIELD section, data RETURN section, data