Learning Cypher

Onofrio Panzarino

• Publisher: Packt Publishing
• Year: 2014
• eBook ISBN: 9781783287758
• Edition: 1
• Topic: Computer Science
• Subtopic: Data Processing
• Index: Computer Science

In Detail

Neo4j is generating much interest among NoSQL database users for its features, performance and scalability, and robustness. The software also provides users with a very natural and expressive graph model and ACID transactions with rollbacks. However, utilizing Neo4j in a real-world project can be difficult compared to a traditional relational database. Cypher fills this gap with SQL, providing a declarative syntax and the expressiveness of pattern matching. This relatively simple but powerful language allows you to focus on your domain instead of getting lost in database access. As you will learn in this book, very complicated database queries can easily be expressed through Cypher.

This book is a practical, hands-on guide to designing, implementing, and querying a Neo4j database quickly and painlessly. Through a number of practical examples, this book uncovers all the behaviors that will help you to take advantage of Neo4j effectively, with tips and tricks to help you along the way. The book starts with the basic clauses and patterns to perform read-only queries with Cypher. You will then learn about clauses and tips that can be used with patterns to elaborate results coming from pattern matching. Next, you will master the clauses required to modify a graph. Once you have got these basics right with the help of practical examples, you will then learn about tools and practices to improve the performance of queries and how to migrate a database to Neo4j from the ground up. To finish off, the book covers Cypher operators and functions in detail.

Approach

An easy-to-follow guide full of tips and examples of real-world applications. In each chapter, a thorough example will show you the concepts in action, followed by a detailed explanation.

Who this book is for

If you want to learn how to create, query, and maintain a graph database, or want to migrate to a graph database from SQL, this is the book for you.

Learning Cypher

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Table of Contents

Learning Cypher

Credits

About the Author

About the Reviewers

www.PacktPub.com

Support files, eBooks, discount offers, and more

Why subscribe?

Free access for Packt account holders

Preface

What this book covers

What you need for this book

Who this book is for

Conventions

Reader feedback

Customer support

Downloading the example code

Errata

Piracy

Questions

1. Querying Neo4j Effectively with Pattern Matching

Setting up a new Neo4j database

Neo4j running modes

Neo4j Server

An embedded database

Preparing the development environment

Creating an embedded database

Configuration

HR management tool – an example

Creating nodes and relationships using the Java API

A querying database

Invoking Cypher from Java

Finding nodes by relationships

Filtering properties

Filtering relationships

Dealing with missing parts

Working with paths

Node IDs as starting points

Query parameters

Passing parameters with Java

Summary

2. Filter, Aggregate, and Combine Results

Filtering

The book store – an example

Text search

Working with regular expressions

Escaping the text

Value comparisons

The IN predicate

Boolean operators

Working with collections

Paging results – LIMIT and SKIP

Sorting

A descending sort

Dealing with null values using the COALESCE function

Aggregating results

Counting matching rows or non-null values

Summation

Average

Maximum and minimum

Standard deviation

Collecting values in an array

Grouping keys

Conditional expressions

Separating query parts using WITH

The UNION statement

Summary

3. Manipulating the Database

Using Neo4j Browser

Creating nodes and relationships

Labels and properties

Multiple labels

Properties

Creating multiple patterns

Creating relationships

Creating full paths

Creating relationships between existing nodes using read-and-write queries

Modifying existing data

Creating unique patterns

Complex patterns

Setting properties and labels

Cloning a node

Adding labels to nodes

Merging matched patterns

Idempotent queries

Deleting data

Removing labels

Removing properties

Deleting nodes and relations

Clearing the whole database

Loops

Working with collections

Summary

4. Improving Performance

Performance issues

Best practices and recommendations

Using parameterized queries

Parameterized queries with the REST API

Reusing ExecutionEngine

Finding the optimum transaction size

Avoiding unnecessary clauses

Specifying the direction of relationships and variable length paths

Profiling queries

Profiling using the Java API

Inside the execution plan description

Profiling with Neo4j Shell

Profiling with the REST API

Indexes and constraints

SCAN hints

Index hints

Constraints

Summary

5. Migrating from SQL

Our example

Migrating the schema

Labels

Indexes and constraints

Relationships

Migrating the data

Entities

Relationships

Migrating queries

CRUD

Searching queries

Grouping queries

Summary

A. Operators and Functions

Operators

Comparison operators

Ordering operators

Equality operators

NULL equality operators

Mathematical operators

The concatenation operator

The IN operator

Regular expressions

Functions

COALESCE

TIMESTAMP

ID

Working with nodes

NODES

LABELS

Working with paths and relationships

TYPE

ENDNODE and STARTNODE

SHORTESTPATH and ALLSHORTESTPATHS

RELATIONSHIPS

Working with collections

HEAD, TAIL, and LAST

LENGTH

EXTRACT

FILTER

REDUCE

RANGE

Working with strings

SUBSTRING, LEFT, and RIGHT

STR

REPLACE

Trimming functions

LOWER and UPPER

Aggregation functions

COUNT

SUM

AVG

PERCENTILEDISC and PERCENTILECONT

STDEV and STDEVP

MIN and MAX

Mathematical functions

Index

Learning Cypher

Copyright © 2014 Packt Publishing

All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, without the prior written permission of the publisher, except in the case of brief quotations embedded in critical articles or reviews.

Every effort has been made in the preparation of this book to ensure the accuracy of the information presented. However, the information contained in this book is sold without warranty, either express or implied. Neither the author, nor Packt Publishing, and its dealers and distributors will be held liable for any damages caused or alleged to be caused directly or indirectly by this book.

Packt Publishing has endeavored to provide trademark information about all of the companies and products mentioned in this book by the appropriate use of capitals. However, Packt Publishing cannot guarantee the accuracy of this information.

First published: May 2014

Production Reference: 1070514

Published by Packt Publishing Ltd.

Livery Place

35 Livery Street

Birmingham B3 2PB, UK.

ISBN 978-1-78328-775-8

www.packtpub.com

Cover Image by Jaroslaw Blaminsky (<[email protected]>)

Credits

Author

Onofrio Panzarino

Reviewers

Riccardo Mancinelli

Rohit Mukherjee

Timmy Storms

Craig Taverner

Commissioning Editor

Antony Lowe

Acquisition Editor

Owen Roberts

Content Development Editor

Priyanka S

Technical Editors

Taabish Khan

Nikhil Potdukhe

Akash Rajiv Sharma

Copy Editors

Mradula Hegde

Gladson Monteiro

Project Coordinator

Harshal Ved

Proofreader

Ameesha Green

Indexer

Mariammal Chettiyar

Graphics

Yuvraj Mannari

Abhinash Sahu

Production Coordinator

Aparna Bhagat

Cover Work

Aparna Bhagat

About the Author

Onofrio Panzarino is a programmer with 15 years experience working with various langua...

Table of contents

• Learning Cypher