使用 Neo4j 和 Go 构建应用程序

go get github.com/neo4j/neo4j-go-driver/v5

// Get the name of all 42 year-olds
result, _ := neo4j.ExecuteQuery(ctx, driver,
    "MATCH (p:Person {age: $age}) RETURN p.name AS name",
    map[string]any{
        "age": "42",
    }, neo4j.EagerResultTransformer,
    neo4j.ExecuteQueryWithDatabase("neo4j"))

// Loop through results and do something with them
for _, record := range result.Records {
    fmt.Println(record.AsMap())
}

// Summary information
fmt.Printf("The query `%v` returned %v records in %+v.\n",
    result.Summary.Query().Text(), len(result.Records),
    result.Summary.ResultAvailableAfter())

package main

import (
    "fmt"
    "context"
    "strconv"
    "errors"
    "github.com/neo4j/neo4j-go-driver/v5/neo4j"
)

func main() {
    ctx := context.Background()
    var employeeThreshold int64 = 10  // Neo4j's integer maps to Go's int64

    // Connection to database
    dbUri := "<URI for Neo4j database>"
    dbUser := "<Username>"
    dbPassword := "<Password>"
    driver, err := neo4j.NewDriverWithContext(
        dbUri,
        neo4j.BasicAuth(dbUser, dbPassword, ""))
    if err != nil {
        panic(err)
    }
    defer driver.Close(ctx)
    err = driver.VerifyConnectivity(ctx)
    if err != nil {
        panic(err)
    }

    session := driver.NewSession(ctx, neo4j.SessionConfig{DatabaseName: "neo4j"})
    defer session.Close(ctx)

    // Create 100 people and assign them to various organizations
    for i := 0; i < 100; i++ {
        name := "Thor" + strconv.Itoa(i)
        orgId, err := session.ExecuteWrite(ctx,
            func(tx neo4j.ManagedTransaction) (any, error) {
                var orgId string

                // Create new Person node with given name, if not exists already
                _, err := tx.Run(
                    ctx,
                    "MERGE (p:Person {name: $name})",
                    map[string]any{
                        "name": name,
                    })
                if err != nil {
                    return nil, err
                }

                // Obtain most recent organization ID and the number of people linked to it
                result, err := tx.Run(
                    ctx, `
                    MATCH (o:Organization)
                    RETURN o.id AS id, COUNT{(p:Person)-[r:WORKS_FOR]->(o)} AS employeesN
                    ORDER BY o.createdDate DESC
                    LIMIT 1
                    `, nil)
                if err != nil {
                    return nil, err
                }
                org, err := result.Single(ctx)

                // If no organization exists, create one and add Person to it
                if org == nil {
                    orgId, _ = createOrganization(ctx, tx)
                    fmt.Println("No orgs available, created", orgId)
                    err = addPersonToOrganization(ctx, tx, name, orgId)
                    if err != nil {
                        return nil, errors.New("Failed to add person to new org")
                        // Transaction will roll back
                        // -> not even Person and/or Organization is created!
                    }
                } else {
                    orgId = org.AsMap()["id"].(string)
                    if employeesN := org.AsMap()["employeesN"].(int64);
                       employeesN == 0 {
                        return nil, errors.New("Most recent organization is empty")
                        // Transaction will roll back
                        // -> not even Person is created!
                    }

                    // If org does not have too many employees, add this Person to it
                    if employeesN := org.AsMap()["employeesN"].(int64);
                       employeesN < employeeThreshold {
                        err = addPersonToOrganization(ctx, tx, name, orgId)
                        if err != nil {
                            return nil, err
                            // Transaction will roll back
                            // -> not even Person is created!
                        }
                    // Otherwise, create a new Organization and link Person to it
                    } else {
                        orgId, err = createOrganization(ctx, tx)
                        if err != nil {
                            return nil, err
                            // Transaction will roll back
                            // -> not even Person is created!
                        }
                        fmt.Println("Latest org is full, created", orgId)
                        err = addPersonToOrganization(ctx, tx, name, orgId)
                        if err != nil {
                            return nil, err
                            // Transaction will roll back
                            // -> not even Person and/or Organization is created!
                        }
                    }
                }
                // Return the Organization ID to which the new Person ends up in
                return orgId, nil
            })
        if err != nil {
            fmt.Println(err)
        } else {
            fmt.Println("User", name, "added to organization", orgId)
        }
    }
}

func createOrganization(ctx context.Context, tx neo4j.ManagedTransaction) (string, error) {
    result, err := tx.Run(
        ctx, `
        CREATE (o:Organization {id: randomuuid(), createdDate: datetime()})
        RETURN o.id AS id
        `, nil)
    if err != nil {
        return "", err
    }
    org, err := result.Single(ctx)
    if err != nil {
        return "", err
    }
    orgId, _ := org.AsMap()["id"]
    return orgId.(string), err
}

func addPersonToOrganization(ctx context.Context, tx neo4j.ManagedTransaction, personName string, orgId string) (error) {
    _, err := tx.Run(
        ctx, `
        MATCH (o:Organization {id: $orgId})
        MATCH (p:Person {name: $name})
        MERGE (p)-[:WORKS_FOR]->(o)
        `, map[string]any{
            "orgId": orgId,
            "name": personName,
        })
    return err
}

driver, err := neo4j.NewDriverWithContext(dbUri, neo4j.BasicAuth(dbUser, dbPassword, ""))
defer driver.Close(ctx)

session := driver.NewSession(ctx, neo4j.SessionConfig{DatabaseName: "neo4j"})
defer session.Close(ctx)