Effectively clear Neo4j database

问题

This is my previous question Clear Neo4j Embedded database

Right now I understand that I don't need to shutdown database, I only need to wipe all data inside of this database.

I use the following method:

public static void cleanDb(Neo4jTemplate template) {
    template.query("MATCH (n) OPTIONAL MATCH (n)-[r]-() DELETE n,r", null);
}

but it's not work properly on a large data sets.

Also, with a new version of Spring Data Neo4j I can't use Neo4jHelper.cleanDb(db);

Is any ways to correctly and effectively clean the database state without database shutdown/deleting ?

UPDATED

I have implemented following util class with cleanDb method

public class Neo4jUtils {

    final static Logger logger = LoggerFactory.getLogger(Neo4jUtils.class);

    private static final int BATCH_SIZE = 10;

    public static void cleanDb(Neo4jTemplate template) {
        logger.info("Cleaning database");

        long count = 0;
        do {
            GraphDatabaseService graphDatabaseService = template.getGraphDatabaseService();
            Transaction tx = graphDatabaseService.beginTx();
            try {
                Result<Map<String, Object>> result = template.query("MATCH (n) WITH n LIMIT " + BATCH_SIZE + " OPTIONAL MATCH (n)-[r]-() DELETE n, r RETURN count(n) as count", null);
                count = (long) result.single().get("count");
                tx.success();
                logger.info("count: " + count);
            } catch (Throwable th) {
                logger.error("Error while deleting database", th);
                throw th;
            } finally {
                tx.close();
            }
        } while (count > 0);

    }

}

right now it hangs on the line:

tx.close();

How to fix it, what am I doing wrong ?

Also, after number of experiments I have noticed that I can clean the database as many times as I want only on the working application. Right after application restart(I kill application process from console) cleanDb method stops working on this existing database and hangs.

No issues in the messages.log, everything looks fine:

2015-07-25 23:06:59.285+0000 INFO  [o.n.k.EmbeddedGraphDatabase]: Database is now ready

I have no idea what can be wrong.. please help to solve this issue.

I use:

neo4j version 2.2.3
lucene version 3.6.2
spring-data-neo4j version 3.4.0.M1

IMPORTANT UPDATE

I noticed that everything work properly if I use graphDatabaseService.shutdown(); method before terminating of my application.. Otherwise database is destroyed(Neo4j server also hangs on this corrupted db).

Is any way to make Neo4j Embedded database more fault tolerant ? I will lose all my data after the first error (for example blackout event) in the production environment..

回答1:

I don't know how it works with Spring Data, but in general you should try to delete nodes/relationships in batches.

Cypher query:

MATCH (n)
WITH n LIMIT 10000
OPTIONAL MATCH (n)-[r]-()
DELETE n, r
RETURN count(n)

In your application you do:

while return_value > 0:
    run_delete_query()

Depending on your memory you can of course increase the LIMIT.

来源：https://stackoverflow.com/questions/31624582/effectively-clear-neo4j-database

标签

neo4j

cypher

spring-data-neo4j