neo4j-go-driver

README

neo4j-go-driver

This is the pre-release version of the official Neo4j Go Driver. It is based on our C Connector, and depends on seabolt to be available on the host system.

Requirements

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

1. seabolt (see requirements here)
2. pkg-config tool for your platform
3. working cgo environment for your platform

Building

Linux (Ubuntu)

1. Make sure you have pkg-config installed via apt install pkg-config
2. Clone seabolt (assume <seabolt_dir> to be the absolute path in which the clone resides) and make sure you can build it successfully (follow it's own instructions)
3. Add/Update environment variable PKG_CONFIG_PATH to include <seabolt_dir>/build
4. Add/Update environment variable LD_LIBRARY_PATH to include <seabolt_dir>/build/lib
5. Get this package via go get github.com/neo4j/neo4j-go-driver/neo4j

MacOS

1. Install pkg-config via brew install pkg-config
2. Clone seabolt (assume <seabolt_dir> to be the absolute path in which the clone resides) and make sure you can build it successfully,
3. Add/Update environment variable PKG_CONFIG_PATH to include build subdirectory of seabolt, i.e. $PKG_CONFIG_PATH:<seabolt_dir>/build
4. Add/Update environment variable LD_LIBRARY_PATH to include <seabolt_dir>/build/lib
5. Go Get this package via go get github.com/neo4j/neo4j-go-driver/neo4j

Windows

1. Install a mingw toolchain (for instance MSYS2 from https://www.msys2.org/) for cgo support (seabolt include some instructions),
2. Clone seabolt (assume <seabolt_dir> to be the absolute path in which the clone resides) and make sure you can build it successfully,
3. Add/Update environment variable PKG_CONFIG_PATH to include build subdirectory of seabolt, i.e. %PKG_CONFIG_PATH%;<seabolt_dir>/build
4. Update environment variable PATH to include <seabolt_dir>/build/bin
5. Go Get this package via go get github.com/neo4j/neo4j-go-driver/neo4j

Versioning

Although master branch contains the source code for the latest available release, we are also tagging releases after semantic versioning scheme so that dep will find latest release and add the driver as a dependency on your project.

Getting the Driver

Add the driver as a dependency with dep.

dep ensure -add github.com/neo4j/neo4j-go-driver/neo4j

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	null
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.