REPL

The ArcFlow REPL is an interactive shell for executing WorldCypher queries and managing the graph database. Launch it with arcflow. Every meta-command starts with :. Any other input is executed as a WorldCypher query.

Starting the REPL#

# In-memory (data lost on exit)
arcflow
 
# Persistent storage (WAL + snapshots, survives restarts)
arcflow --data-dir ./mydb
 
# Persistent with demo data preloaded
arcflow --data-dir ./mydb --playground

On startup, the REPL prints a welcome banner:

  ArcFlow 0.1.0 — graph database engine

  Quick start:
    CALL db.demo            Load sample graph
    MATCH (n) RETURN n      Query everything
    CALL algo.pageRank()     Run an algorithm
    CALL db.help             Full procedure guide
    CALL db.tutorial         Interactive walkthrough

  Type :quit to exit

arcflow>

Executing Queries#

Type any WorldCypher query at the arcflow> prompt. Results display as a formatted table.

arcflow> CREATE (n:Person {name: 'Alice', age: 30}) RETURN n
+----+---
-----+-----+
| n  | n.name | n.age |
+----+---
-----+-----+
| 0  | Alice  | 30  |
+----+---
-----+-----+
1 row

arcflow> MATCH (n:Person) RETURN n.name, n.age
+---
-----+-----+
| n.name | n.age |
+---
-----+-----+
| Alice  | 30  |
+---
-----+-----+
1 row

Meta-Command Reference#

Every meta-command begins with : and is case-sensitive. Arguments are space-separated.

:help#

Show the quick reference for queries, algorithms, and shell commands.

arcflow> :help
ArcFlow Quick Reference

  Getting Started
    CALL db.demo             Load sample graph
    CALL db.tutorial         Interactive 6-step walkthrough
    CALL db.help             Full procedure guide with examples

  Queries
    MATCH (n:Label) RETURN n
    MATCH (n) WHERE n.age > 25 RETURN n.name
    CREATE (n:Person {name: 'Alice'}) RETURN n
    MATCH (a)-[:KNOWS]->(b) RETURN b.name

  Algorithms
    CALL algo.pageRank()             PageRank
    CALL algo.louvain()              Community detection
    CALL algo.connectedComponents()  Find subgraphs
    CALL algo.graphRAG('query')      GraphRAG pipeline

  Shell Commands
    :status    Engine status       :demo      Load demo data
    :schema    Full schema         :bench     Run benchmark
    :count     Node/rel counts     :clear     Reset database
    :dump      Export as CREATE     :quit      Exit

:status#

Show engine backend, node count, relationship count, and generation counter.

arcflow> :status
Backend: cpu (CPU backend active)
Nodes: 12
Relationships: 15
Generation: 27

:count#

Quick summary of node, relationship, and skill counts.

arcflow> :count
Nodes: 12
Relationships: 15
Skills: 3

:schema#

Full database schema: labels with node counts, relationship types, property keys, indexes, and constraints.

arcflow> :schema
=== WorldCypher Schema ===

Labels:
  :Person (5 nodes)
  :Company (3 nodes)
  :Project (4 nodes)

Relationship Types:
  :WORKS_AT
  :KNOWS
  :MANAGES

Property Keys:
  name
  age
  title

Indexes:
  INDEX ON :Person(name)

Constraints:
  UNIQUE ON :Person(email)

Skills: 3

:labels#

List all node labels with counts.

arcflow> :labels
  :Person (5 nodes)
  :Company (3 nodes)
  :Project (4 nodes)

On an empty graph:

arcflow> :labels
No labels

:types#

List all relationship types.

arcflow> :types
  :WORKS_AT
  :KNOWS
  :MANAGES

On an empty graph:

arcflow> :types
No relationship types

:keys#

List all property keys in the graph.

arcflow> :keys
  name
  age
  title
  email

On an empty graph:

arcflow> :keys
No property keys

:indexes#

List all indexes.

arcflow> :indexes
  INDEX ON :Person(name)
  INDEX ON :Company(domain)

On an empty graph:

arcflow> :indexes
No indexes defined

:constraints#

List all uniqueness constraints.

arcflow> :constraints
  UNIQUE ON :Person(email)

On an empty graph:

arcflow> :constraints
No constraints defined

:stats#

Detailed engine statistics including node/relationship counts, skill count, index count, generation, backend, and data directory.

arcflow> :stats
=== WorldCypher Engine Stats ===
Nodes:         12
Relationships: 15
Skills:        3
Indexes:       2
Generation:    27
Backend:       cpu
Data dir:      ./mydb

:bench#

Run a performance benchmark: creates 1000 nodes, times count/filter/aggregation queries, then cleans up. Results include throughput in nodes/sec and query latency in microseconds.

arcflow> :bench
Running benchmark...

Create 1000 nodes:     45 ms (22222 nodes/sec)
Count all:           12 μs → 1000
Filter (idx > 500):  18 μs → 499
Aggregation (avg):   15 μs
Delete 1000 nodes:    30 ms

Benchmark complete.

:demo#

Load a sample graph with Person, Company, and Project nodes connected by relationships. Useful for exploration.

arcflow> :demo
Loaded demo data: 12 nodes, 15 relationships

:dump#

Export the entire graph as WorldCypher CREATE statements. Includes indexes, constraints, nodes, and relationships.

arcflow> :dump
-- WorldCypher dump
-- Nodes: 12, Relationships: 15

CREATE INDEX ON :Person(name);
CREATE CONSTRAINT ON :Person(email) ASSERT UNIQUE;
CREATE (n:Person {name: 'Alice', age: 30});
CREATE (n:Person {name: 'Bob', age: 25});
CREATE (n:Company {name: 'Acme'});
-- REL 0 -[:WORKS_AT]-> 2
-- REL 1 -[:WORKS_AT]-> 2

-- End dump

:clear#

Delete all nodes, relationships, indexes, constraints, and skills. Irreversible.

arcflow> :clear
Database cleared.

:checkpoint#

Force a WAL checkpoint by writing the current graph state to the snapshot file. Only works when --data-dir is set.

arcflow> :checkpoint
Checkpoint saved.

Without --data-dir:

arcflow> :checkpoint
No --data-dir set. Use --data-dir to enable persistence.

:import csv <file> <Label>#

Bulk-import a CSV file. The first row is treated as column headers (property keys). Each subsequent row becomes a node with the specified label. Values are auto-typed: integers, floats, or strings.

Syntax: :import csv <path-to-file.csv> <NodeLabel>

arcflow> :import csv ./users.csv User
Imported 150 rows as :User nodes

:export json <path>#

Export the graph as a JSON snapshot file.

arcflow> :export json ./backup.json
Exported to ./backup.json (4523 bytes)

:export graphml <path>#

Export the graph as a GraphML XML file.

arcflow> :export graphml ./graph.graphml
Exported GraphML to ./graph.graphml (8192 bytes)

:snapshot <path>#

Save the current graph state to a JSON snapshot file. Identical format to :export json.

arcflow> :snapshot ./backup.json
Snapshot saved to ./backup.json (4523 bytes)

:restore <path>#

Restore graph state from a JSON snapshot file. Replaces the current graph entirely.

arcflow> :restore ./backup.json
Restored: 12 nodes, 15 relationships, 3 skills

:cache#

Display query plan cache statistics: number of cached plans, hit/miss counts, and hit rate.

arcflow> :cache
Query Plan Cache:
  cached plans: 8
  hits:         42
  misses:       12
  hit rate:     77.8%

:quit / :q / :exit#

Exit the REPL. If --data-dir is set and mutations occurred, the graph is auto-saved before exit. Ctrl+D (EOF) also exits.

arcflow> :quit

For AI Agents#

AI coding agents should not use the interactive REPL. Use non-interactive modes instead.

Single-query execution#

Pass a query directly as a CLI argument. Use --json for machine-parseable output.

# Human-readable table output
arcflow query "MATCH (n:Person) RETURN n.name, n.age"
 
# JSON output (preferred for agents)
arcflow query "MATCH (n:Person) RETURN n.name, n.age" --json

JSON output format:

{
  "columns": ["n.name", "n.age"],
  "rows": [
    {"n.name": "Alice", "n.age": "30"},
    {"n.name": "Bob", "n.age": "25"}
  ]
}

Error format:

{"error": true, "code": "EXEC_ERR", "message": "Unknown label: Foo"}

Parameterized queries#

Bind parameters with --param key=value. Reference them with $key in the query.

arcflow query "MATCH (n:Person) WHERE n.name = \$name RETURN n" \
  --param name=Alice --json

Piping queries via stdin#

For batch execution, pipe queries line by line. Each line is executed independently.

echo "MATCH (n) RETURN count(*)" | arcflow

Persistent storage#

Always pass --data-dir for durable state across invocations:

arcflow query "CREATE (n:Person {name: 'Alice'})" --data-dir ./mydb --json
arcflow query "MATCH (n:Person) RETURN n.name" --data-dir ./mydb --json

Health check#

arcflow doctor --json

{"version":"0.1.0","crate_count":8,"workspace_valid":true,"data_dir":".","data_dir_writable":true,"backend":"cpu","status":"ok"}

Path discovery#

arcflow paths --json

{"data_dir":".","wal_path":"./worldcypher.wal","snapshot_path":"./worldcypher.snapshot.json","workspace_root":"/home/user/project","config_path":".arcflow/config.yaml","crate_count":8,"version":"0.1.0"}

Agent context synthesis#

Get full engine context (schema, capabilities, stats) in one call:

arcflow agent-context synth --json --data-dir ./mydb

{"version":"0.1.0","backend":"cpu","node_count":12,"rel_count":15,"labels":["Person","Company"],"rel_types":["WORKS_AT","KNOWS"],"procedure_count":68,"algorithm_count":20,"observation_classes":["observed","inferred","predicted"],"replication_mode":"standalone","clock_domains":["wall"],"capabilities":["pageRank","louvain","graphRAG"]}

Decision tree for agents#

1. Need schema or capabilities? Use arcflow agent-context synth --json.
2. Need to run a single query? Use arcflow query "..." --json.
3. Need a server for multiple queries? Use arcflow --http 8080 and POST to /query.
4. Need MCP integration? Use arcflow-mcp --data-dir ./mydb over stdio.

See Also#

• Server Modes — TCP, HTTP, and MCP access
• Snapshot & Restore