背景

最近需要对公司 hgraphdb hbase 存储替换为neo4j，为了提高查询效率，需要对某些标签下 Node 的属性创建索引，官方提供的材料没有提供 create if not exist，所以需要手动去判断索引存在性，然后写入索引，方法抽取如下：

    public static final Function3<String, String, Session, Boolean> INDEX_EXIST_FUNC = (label, property, session) -> {
        boolean flag = false;
        try {
            flag = session.run(String.format(
                    "CALL db.indexes() YIELD properties,labelsOrTypes where '%s' in labelsOrTypes and '%s' in properties  RETURN count(*) as count",
                    label, property)).list().get(0).get("count", 0) == 0;

        } catch (Exception e) {
            logger.error("check index exist failure=> label = {},property= {}", label, property);
        }
        return flag;
    };

    public static final Function3<String, String, Session, Result> CREATE_INDEX_FUN = (label, property, session) -> {
        synchronized (Clazz.class) {
            if (INDEX_EXIST_FUNC.apply(label, property, session)) {
                session.run(String.format("CREATE INDEX ON :%s(%s)", label, property));
            }
            return null;
        }
    };

依赖包

<!-- https://mvnrepository.com/artifact/io.vavr/vavr -->
<dependency>
    <groupId>io.vavr</groupId>
    <artifactId>vavr</artifactId>
    <version>0.10.3</version>
</dependency>
<dependency>
     <groupId>org.neo4j.driver</groupId>
     <artifactId>neo4j-java-driver</artifactId>
     <version>4.1.0</version>
 </dependency>