Graph Databases
We have first cited the graph data model in the Introduction to Big Data note. Until now, we have explored many aspects of relational data bases, but now we are changing the data model completely. The main reason driving this discussion are the limitations of classical relational databases: queries like traversal of a high number of relationships, reverse traversal requiring also indexing foreign keys (need double index! Index only work in one direction for relationship traversal, i.e. if you need both direction you should build an index both for the forward key and backward key), looking for patterns in the relationships, are especially expensive when using normal databases. We have improved over the problem of joining with relational database using Document Stores with three data structure, but these cannot have cycles. We call index-free adjacency: we use physical memory pointers to store the graph. ...