问题
I know that neo4j stores data structured in graphs rather than in tables. In RDBMS we will be having schemas of the tables but in neo4j we will not be having the tables. Only nodes, relations and properties are defined. So is there any concept of metadata in neo4j. Like is there any information stored about nodes, relationships in the database? If yes, how and what it stores in the metadata? Also where can we find the metadata related information in the graph database (location)
Thanks,
回答1:
Neo4J doesn't directly store metadata in the way that you're looking for. The NeoProfiler tool was written precisely for this purpose. You can run it on a Neo4J database, and it will pull out as much information on labels, indexes, constraints, properties, nodes, and relationships as it can. The way that this works isn't too far off of the queries that @ulkas suggests in the other answer here, the output is just much better.
More broadly, in an RDBMS the schema information you pull out substantially constrains the database. The schema there is like a set of rules; you can't insert data unless it conforms to that schema. In Neo4J, because it's so flexible, even if there was a schema it would just be documentation of what's there, it would not be a set of constraints on what you can put in. At any time, you can insert new data that has nothing to do with the present schema (except that you can't violate things like uniqueness constraints).
If you want to see an equivalent schema for your database in neo4j, check out neoprofiler linked above. A few people out there have written about "metagraphs" - that is, they talk about representing a neo4j schema as a graph itself, where for example a node refers to a label. Relationships from that "label node" then go out to other kinds of label nodes, specifying what sorts of relationships can exist between nodes. For example, nodes labeled "Employee" may frequently have "works_for" relationships to nodes of label "Company".
回答2:
no, direct metadata are not present. the maximum you can do is to query all the structure types and have a small inside what kind of graph could be stored in the db.
START r=rel(*)
RETURN type(r), count(*)
START n=node(*)
RETURN labels(n), count(*)
the specific database files are stored in the folder data/graph.db but besides some index and key files they are binary and not easy to read.
来源：https://stackoverflow.com/questions/24931059/metadata-in-neo4j-graph-database