neo4j-go-driver

README

neo4j-go-driver

This is the the official Neo4j Go Driver. It is built on our C Connector, seabolt and depends on it to be available on the host system.

Requirements

This package requires the following tools/libraries to be installed in order to be built.

1. C Compiler Toolchain
2. seabolt
3. pkg-config tool for your platform

Requirements

Compiler Toolchain

Install C/C++ compiler toolchain supported by your operating system. You'll need a mingw toolchain (for instance MSYS2 from https://www.msys2.org/) for cgo support (seabolt includes instructions) on Windows.

Pkg-Config

Linux distributions provide pkg-config as part of their package management systems (apt install pkg-config or yum install pkgconfig).

MacOS doesn't provide pkg-config, so have it installed through brew install pkg-config.

Windows doesn't provide pkg-config, so have it installed by following these instructions, make the bin folder available in PATH before any MSYS2 PATH entries. This is mandatory because pkg-config that ships with MSYS2 has some path handling problems

Seabolt

Binaries

We're now providing experimental binaries for Linux, MacOS and Windows here. Please remember that OpenSSL is a required dependency for Linux and MacOS - TLS on Windows depends on native SCHANNEL provider and doesn't require any additional third-party dependencies from version 1.7.3 onwards.

Source

Clone seabolt (assume <seabolt_dir> to be the absolute path in which the clone resides) and build it using one the provided make_debug.[sh|cmd] or make_release.[sh|cmd] scripts. The scripts set the installation path to <seabolt_dir>/build/dist and <seabolt_install_dir> in the following steps refer to it.

Set PKG_CONFIG_PATH to <seabolt_install_dir>/share/pkgconfig on Linux/MacOS or to <seabolt_install_dir> on Windows.

Set LD_LIBRARY_PATH/DYLD_LIBRARY_PATH to include <seabolt_install_dir>/lib on Linux/MacOS respectively. This is not necessary if you will link statically to seabolt or use RPATH feature on your platform (see below).

Add <seabolt_install_dir>\bin to PATH environment variable on Windows.

Getting the Driver

With dep

Add the driver as a dependency with dep ensure -add github.com/neo4j/neo4j-go-driver/neo4j

With go get

Add the driver with go get github.com/neo4j/neo4j-go-driver/neo4j

Static Linking

We provide seabolt_static build tag to support static linking against seabolt and its dependencies. You can just pass --tags seabolt_static to your go toolset (like go build --tags seabolt_static) for your project and the generated binary will not have any runtime dependencies to seabolt.

Setting RPATH on Linux/MacOS

Both Linux and MacOS dynamic loader support RPATH entries into executables so that they can locate their dependent shared libraries based on those entries. To have a RUNPATH entry to be added to your executable, you can pass -ldflags "-r $(pkg-config --variable=libdir seabolt17)" to your go toolset (like go build -ldflags "-r $(pkg-config --variable=libdir seabolt17)") and it will add an RPATH entry to your executable that points to the location where seabolt shared library resides.

Minimum Viable Snippet

Connect, execute a statement and handle results

var (
	driver neo4j.Driver
	session neo4j.Session
	result neo4j.Result
	err error
)

if driver, err = neo4j.NewDriver("bolt://localhost:7687", neo4j.BasicAuth("username", "password", "")); err != nil {
	return err // handle error
}
// handle driver lifetime based on your application lifetime requirements
// driver's lifetime is usually bound by the application lifetime, which usually implies one driver instance per application
defer driver.Close()

if session, err = driver.Session(neo4j.AccessModeWrite); err != nil {
	return err
}
defer session.Close() 

result, err = session.Run("CREATE (n:Item { id: $id, name: $name }) RETURN n.id, n.name", map[string]interface{}{
	"id": 1,
	"name": "Item 1",
})
if err != nil {
	return err // handle error
}

for result.Next() {
	fmt.Printf("Created Item with Id = '%d' and Name = '%s'\n", result.Record().GetByIndex(0).(int64), result.Record().GetByIndex(1).(string))
}
if err = result.Err(); err != nil {
	return err // handle error
}

Connecting to a causal cluster

You just need to use bolt+routing as the URL scheme and set host of the URL to one of your core members of the cluster.

if driver, err = neo4j.NewDriver("bolt+routing://localhost:7687", neo4j.BasicAuth("username", "password", "")); err != nil {
	return err // handle error
}

There are a few points that need to be highlighted:

• Each Driver instance maintains a pool of connections inside, as a result, it is recommended to only use one driver per application.
• It is considerably cheap to create new sessions and transactions, as sessions and transactions do not create new connections as long as there are free connections available in the connection pool.
• The driver is thread-safe, while the session or the transaction is not thread-safe.

Parsing Result Values

Record Stream

A cypher execution result is comprised of a stream of records followed by a result summary. The records inside the result can be accessed via Next()/Record() functions defined on Result. It is important to check Err() after Next() returning false to find out whether it is end of result stream or an error that caused the end of result consumption.

Accessing Values in a Record

Values in a Record can be accessed either by index or by alias. The return value is an interface{} which means you need to convert the interface to the type expected

value := record.GetByIndex(0)

if value, ok := record.Get('field_name'); ok {
	// a value with alias field_name was found
	// process value
}

Value Types

The driver currently exposes values in the record as an interface{} type. The underlying types of the returned values depend on the corresponding Cypher types.

The mapping between Cypher types and the types used by this driver (to represent the Cypher type):

Cypher Type	Driver Type
null	nil
List	[]interface{}
Map	map[string]interface{}
Boolean	bool
Integer	int64
Float	float
String	string
ByteArray	[]byte
Node	neo4j.Node
Relationship	neo4j.Relationship
Path	neo4j.Path

Spatial Types - Point

Cypher Type	Driver Type
Point	neo4j.Point

The temporal types are introduced in Neo4j 3.4 series.

You can create a 2-dimensional Point value using;

point := NewPoint2D(srId, 1.0, 2.0)

or a 3-dimensional Point value using;

point := NewPoint3D(srId, 1.0, 2.0, 3.0)

NOTE:

• For a list of supported srId values, please refer to the docs here.

Temporal Types - Date and Time

The temporal types are introduced in Neo4j 3.4 series. Given the fact that database supports a range of different temporal types, most of them are backed by custom types defined at the driver level.

The mapping among the Cypher temporal types and actual exposed types are as follows:

Cypher Type	Driver Type
Date	neo4j.Date
Time	neo4j.OffsetTime
LocalTime	neo4j.LocalTime
DateTime	time.Time
LocalDateTime	neo4j.LocalDateTime
Duration	neo4j.Duration

Receiving a temporal value as driver type:

dateValue := record.GetByIndex(0).(neo4j.Date)

All custom temporal types can be constructing from a time.Time value using <Type>Of() (DateOf, OffsetTimeOf, ...) functions.

dateValue := DateOf(time.Date(2005, time.December, 16, 0, 0, 0, 0, time.Local)

Converting a custom temporal value into time.Time (all neo4j temporal types expose Time() function to gets its corresponding time.Time value):

dateValueAsTime := dateValue.Time()

Note:

• When neo4j.OffsetTime is converted into time.Time or constructed through OffsetTimeOf(time.Time), its Location is given a fixed name of Offset (i.e. assigned time.FixedZone("Offset", offsetTime.offset)).
• When time.Time values are sent/received through the driver, if its Zone() returns a name of Offset the value is stored with its offset value and with its zone name otherwise.

Logging

Logging at the driver level can be configured by setting Log field of neo4j.Config through configuration functions that can be passed to neo4j.NewDriver function.

Console Logger

For simplicity, we provide a predefined console logger which can be constructed by neo4j.ConsoleLogger function. To enable console logger, you need to specify which level you need to enable (neo4j.ERROR, neo4j.WARNING, neo4j.INFO and neo4j.DEBUG which are ordered by the level of detail).

A simple code snippet that will enable console logging is as follows;

useConsoleLogger := func(level neo4j.LogLevel) func(config *neo4j.Config) {
	return func(config *neo4j.Config) {
		config.Log = neo4j.ConsoleLogger(level)
	}
}

// Construct a new driver
if driver, err = neo4j.NewDriver(uri, neo4j.BasicAuth(username, password, ""), useConsoleLogger(neo4j.ERROR)); err != nil {
	return err
}
defer driver.Close()

Custom Logger

The Log field of the neo4j.Config struct is defined to be of interface neo4j.Logging which has the following definition.

type Logging interface {
	ErrorEnabled() bool
	WarningEnabled() bool
	InfoEnabled() bool
	DebugEnabled() bool

	Errorf(message string, args ...interface{})
	Warningf(message string, args ...interface{})
	Infof(message string, args ...interface{})
	Debugf(message string, args ...interface{})
}

For a customised logging target, you can implement the above interface and pass an instance of that implementation to the Log field.