Neo4J embeddings on a read-only neo4j instance

[SimonSuewerUHH]

Good afternoon, nice team.

I am trying to use neo4j as an embedding store. However, I want to do this in a read-only context. This means that the embeddings are all set beforehand and the application is then only run in read mode in production.

In fact, we first set all indexes and constraints so that we pass the createSchema functions.

I wonder if it is possible to read embeddings only, or if this is not intended. If this is not currently possible, I would suggest introducing an optional readMode which, when set, would prevent corresponding write operations from being executed with optional logging.

Error itself.

Caused by: org.neo4j.driver.exceptions.ClientException: No write operations are allowed on this database. The database is in read-only mode on this Neo4j instance.
	at org.neo4j.driver.internal.util.Futures.blockingGet(Futures.java:63)
	at org.neo4j.driver.internal.InternalResult.blockingGet(InternalResult.java:116)
	at org.neo4j.driver.internal.InternalResult.consume(InternalResult.java:95)
	at dev.langchain4j.community.store.embedding.neo4j.Neo4jEmbeddingStore.lambda$bulk$3(Neo4jEmbeddingStore.java:596)
	at org.neo4j.driver.internal.InternalSession.lambda$execute$4(InternalSession.java:161)
	at org.neo4j.driver.internal.InternalSession.lambda$transaction$5(InternalSession.java:178)
	at org.neo4j.driver.internal.retry.ExponentialBackoffRetryLogic.retry(ExponentialBackoffRetryLogic.java:114)
	at org.neo4j.driver.internal.InternalSession.transaction(InternalSession.java:175)
	at org.neo4j.driver.internal.InternalSession.execute(InternalSession.java:160)
	at org.neo4j.driver.internal.InternalSession.executeWrite(InternalSession.java:132)
	at org.neo4j.driver.Session.executeWrite(Session.java:169)
	at dev.langchain4j.community.store.embedding.neo4j.Neo4jEmbeddingStore.lambda$bulk$4(Neo4jEmbeddingStore.java:596)

I hope you can help me with this.

Many thanks and best regards,
Simon

[geoand]

Hello,

Maybe I am missing something, but if you don't ingest anything in the application, then the application will simply be reading from Neo4J and will never write anything.

cc @jmartisk

[jmartisk]

I guess the stack trace is missing some parts, it's not clear what triggered the write. Is it trying to create an index? A unique constraint? Both of these should be detected if they already exist (and you have set the label, id-property and index-name properties of the embedding store).

[SimonSuewerUHH]

Hi, thank you for your reply. The write can be seen in the first screenshot. The bulk is executed at each "embeddingModel.embed(query).content();"
Although I'm not sure if the langchain4j repo might be a better place for this thread.

[jmartisk]

I don't understand, I guess I would need to see the actual code. embeddingModel.embed(query).content(); only works with an embedding model, which can be anything and is not tied to Neo4j at all. Mere computation of an embedding does not store anything into the database, it's just computing the vector.

The only place in https://github.com/langchain4j/langchain4j-community/blob/main/embedding-stores/langchain4j-community-neo4j/src/main/java/dev/langchain4j/community/store/embedding/neo4j/Neo4jEmbeddingStore.java where the bulk method is called is the addAll method, which, as its name implies, adds embeddings into a database, which obviously requires write access, so it seems you are calling addAll somewhere. But without seeing the code or a reproducer (or at least the full stack trace), I'm just guessing.

Sure, if you prefer filing it in https://github.com/langchain4j/langchain4j-community, there you will find people who know the Neo4j embedding store better :)