memgraph | source graph database , built for real-time streaming data

While Memgraph is not an RDF store, it is capable of handling this kind of data with the labeled property graph model (LPG). LPG is represented by a set of nodes, relationships, properties (key-value attributes) and labels. RDF statements can be directly treated as nodes, relationships and properties of the graph, which are explored using the Cypher query language. Therefore, both RDF and LPG allow the creation of a knowledge graph.

While running, Memgraph generates several different files in its data directory. This is the location where Memgraph saves all permanent data. The default data directory is /var/lib/memgraph.

If you want to trigger creating a snapshot of the current database state, run the following query in mgconsole or Memgraph Lab:

You can achieve this behavior using labels. For example, you can add the label GraphOne to each node of the first graph, the label GraphTwo to each node of the second graph, and so on. Nodes can have multiple labels, so you can still keep the original labels and the new ones that tell you which graph a specific node belongs to. You can use the same technique to save multilayer networks.

Aside from this method, the only other option is to fire up a new instance.

If you are worried about lots of metadata, the label will not use up a lot of memory, so not much overhead is added. Additional security can be implemented by requiring the use of these labels in each query. For example, if you are connecting with GQLAlchemy, you check each query to see if it contains an appropriate label (GraphOne, GraphTwo, etc.) and throw an error if it's not included.

You should check the Memgraph logs, where you'll probably find the reason why the process was aborted.

Since you said that you're using Memgraph with Docker, there are two options:

1. If you run Memgraph with Docker using the volume for logs, that is with -v mg_log:/var/log/memgraph, then mg_log folder usually can be found at \\wsl$\docker-desktop-data\version-pack-data\community\docker\volumes\ (Windows) or /var/lib/docker/volumes/ (Linux and macOS).

2. If you run Memgraph without using the volume for logs, then you need to enter the Docker container. In order to do that, first you have to find out the container ID by running docker ps. Then you have to copy the container ID and run docker exec -it bash. For example, if container ID is 83d76fe4df5a, then you run docker exec -it 83d76fe4df5a bash. Next, you need find the folder where logs are located. You can do that by running cd /var/log/memgraph. To read the logs, run cat .log, that is, if you have log file memgraph_2022-03-02.log located inside the log folder, then run cat memgraph_2022-03-02.log.

Hopefully, when you read the logs, you'll be able to fix your problem.

Basic authentication is supported in the non-enterprise version. You should be able to create a password-protected user with the following query:

You can try running the FREE MEMORY query which tries to free unused memory chunks in different parts of the storage.

You can export your graph by using Memgraph Lab. If using the memgraph/memgraph-platform Docker image, you should be able to access Memgraph Lab locally in your browser at http://localhost:3000/ .

While on the Overview tab, search for the option Export database in the upper right corner.

It will download the graph.cypherl file

Memgraph uses two mechanisms to ensure data durability:

• write-ahead logs (WAL) and
• periodic snapshots.

Snapshots are taken periodically during the entire runtime of Memgraph. When a snapshot is triggered, the whole data storage is written to the disk. Write-ahead logs save all database modifications that happened to a file. When running Memgraph with Docker, both of these mechanisms rely on the user to create volumes that will store this data when starting Memgraph.

There are two fields to specify for each volume. The first is the name of the volume, and it's unique on a given host machine. In your case, that would be mg_lib, mg_log, and mg_etc. The second field is the path where the file or directory is mounted in the container. In the case of Memgraph, that would be:

• /var/lib/memgraph (this is where the durability related files are saved)
• /var/log/memgraph (logs)
• /etc/memgraph (configuration settings)

Given these paths, the command to run Memgraph with Docker is:

Yep, in the case of this error, the code should retry the query. I think an equivalent issue can happen in Neo4j, but since Memgraph is more optimistic about locking, sometimes the error might happen more often. In general, the correct approach is to have error handling for this case implemented.