Subgraphs

CypherLite treats subgraphs as first-class entities. You can capture a snapshot of part of your graph, give it a name, and query it later. This is useful for versioning, analysis, and isolating graph regions.

Overview

A subgraph is a named collection of nodes and edges stored alongside the main graph. Subgraphs are created from the current state of the graph using a snapshot mechanism.

Key concepts:

• SubgraphStore manages named subgraphs as first-class entities
• CREATE SNAPSHOT captures the current state of matched nodes and edges
• MATCH SNAPSHOT queries a previously saved subgraph
• Subgraphs are immutable once created

Creating a Subgraph

Use CREATE SNAPSHOT to capture a subgraph:

MATCH (p:Person)-[r:KNOWS]->(friend:Person)
WHERE p.name = 'Alice'
CREATE SNAPSHOT 'alice_network'

This captures all nodes and edges matching the pattern into a named subgraph called alice_network.

What Gets Captured

• All nodes matching the pattern
• All relationships matching the pattern
• All properties on those nodes and relationships at the time of capture
• The snapshot is a point-in-time copy; later changes to the original nodes do not affect the snapshot

Querying a Subgraph

Use MATCH SNAPSHOT to query a saved subgraph:

MATCH SNAPSHOT 'alice_network'
(p:Person)-[r:KNOWS]->(friend:Person)
RETURN p.name, friend.name, r.since

This runs the pattern match against only the nodes and edges in the alice_network subgraph, not the full graph.

Use Cases

Graph Versioning

Capture snapshots at key milestones to preserve the graph state:

-- Before a batch import
MATCH (n) CREATE SNAPSHOT 'pre_import_2024'
 
-- After the import, compare
MATCH SNAPSHOT 'pre_import_2024' (n:Person)
RETURN count(n) AS before_count

Analysis Isolation

Isolate a region of the graph for focused analysis:

-- Capture the fraud-suspect subgraph
MATCH (a:Account)-[t:TRANSFERRED]->(b:Account)
WHERE t.amount > 10000
CREATE SNAPSHOT 'high_value_transfers'
 
-- Analyze the isolated subgraph
MATCH SNAPSHOT 'high_value_transfers'
(a:Account)-[t:TRANSFERRED]->(b:Account)
RETURN a.id, b.id, sum(t.amount) AS total

Comparison

Compare two snapshots of the same region at different times:

-- Snapshot from January
MATCH SNAPSHOT 'network_jan' (p:Person)
RETURN count(p) AS jan_count
 
-- Snapshot from June
MATCH SNAPSHOT 'network_jun' (p:Person)
RETURN count(p) AS jun_count

Storage

Subgraphs are stored in the SubgraphStore, which lives alongside the main node and edge storage. Each subgraph entry contains:

Limitations

• Subgraphs are immutable; you cannot add or remove nodes from an existing snapshot
• Deleting a subgraph removes only the snapshot metadata, not the original nodes/edges
• Subgraph names must be unique within a database