Database Reference
In-Depth Information
ture to look up which nodes were connected in the first place. Only then would they be
able to go off and access the nodes. Index-free adjacency allows for query times that are
proportional to how much of the graph you search through, rather than to the overall size
of the graph.
Recall the football stadium analogy from the sidebar in
chapter 1
—“What is the secret of
Neo4j's speed?”
Imagine yourself cheering on your team at a small local football stadium. If someone
asks you how many people are sitting 15 feet around you, you'll get up and count
them—you'll count people around you as fast as you can count. Now imagine you're
attendingthegameatthenationalstadium,withalotmorespectators,andyouwantto
answer the same question—how many people are there within 15 feet of you. Given
that the density of people in both stadiums is the same, you'll have approximately the
samenumberofpeopletocount,takingaverysimilartime.Wecansaythatregardless
ofhowmanypeoplecanfitintothestadium,you'llbeabletocountthepeoplearound
you at a predictable speed; you're only interested in the people sitting 15 feet around
you, so you won't be worried about packed seats on the other end of the stadium, for
example.
This analogy provides a practical demonstration of how a human would naturally employ
the index-free adjacency principle to perform the counting task.
Store files are located under the main graph database directory (by default, data/graph.db
inaserversetup)andareprefixedwithneostore.
Table 11.1
showsthemainstorefilesused
by Neo4j, as well as some of their key properties.
Table 11.1. Primary store files in use and their associated properties
Store filename
Record size
Contents
neostore.nodestore.db
14 bytes
Nodes
neostore.relationshipstore.db
33 bytes
Relationships
Simple (primitive and inlined strings) proper-
ties for nodes and relationships
neostore.propertystore.db
41 bytes
neostore.propertystore.db.arrays
120 + 8 bytes
neostore.propertystore.db.strings
120 + 8 bytes
