Myujth

I got empty result error when accessing neo4j database with the following setup.

• Neo4j runs in docker.


• Uploader process runs continuously with 0.5 second sleep between each
  upload


• Reader process runs continuously as well

Reader:

Driver driver = GraphDatabase.driver("bolt://db_address:7687", AuthTokens.basic("user", "password"));
while (true) 
 try (Session session = driver.session(AccessMode.READ)) 
 for (int i = 1; i <= 100; i++) 
 session.run("Match (n:Number) where n.value=$value return ID(n)", parameters("value", i)).single().get(0).asInt();
 
 
 Thread.sleep(500);

Uploader:

Driver driver = GraphDatabase.driver("bolt://db_address:7687", AuthTokens.basic("user", "password"));
while (true) 
 try (Session session = driver.session(AccessMode.WRITE)) 
 try (Transaction tx = session.beginTransaction()) 
 tx.run("MATCH (n) DELETE n");
 for (int i = 1; i <= 100; i++) 
 tx.run("CREATE (n:Number value: $value) return ID(n)", parameters("value", i)).single().get(0).asInt();
 
 tx.success();
 
 
 Thread.sleep(500);

After few cycles I get error in the reader process:
Cannot retrieve a single record, because this result is empty.

At start the database contains the requested data.
Based on the description of "write transaction" and the code above the empty result seems strange.

Did I miss something with the transaction handling with neo4j?

You need to call tx.success() to commit the transaction.

PS: not sure why the database is cleared on every upload run