Databases Flashcards
What is RDF4J?
Eclipse RDF4J (formerly OpenRDF Sesame) is an open-source framework for storing, querying, and analyzing RDF data.
In SQL relational database terms, RDF data can also be considered a table with three columns – the subject column, the predicate column, and the object column.
What does RDF4J contain?
It contains implementations of an in-memory triplestore and an on-disk triplestore, along with two separate Servlet packages that can be used to manage and provide access to these triplestores, on a permanent server.
What languages does RDF4J support?
RDF4J supports two query languages: SPARQL and SeRQL.
What is SPARQL?
An RDF query language—that is, a semantic query language for databases—able to retrieve and manipulate data stored in Resource Description Framework (RDF) format.
What does SPARQL allow?
SPARQL allows for a query to consist of triple patterns, conjunctions, disjunctions, and optional patterns against what can loosely be called “key-value” data or, more specifically, data that follow the RDF specification of the W3C. Thus, the entire database is a set of “subject-predicate-object” triples. This is analogous to some NoSQL databases’ usage of the term “document-key-value”, such as MongoDB.
What is Amazon Neptune?
A fast, reliable, fully-managed graph database service that makes it easy to build and run applications that work with highly connected datasets.
The core of Neptune is a purpose-built, high-performance graph database engine optimized for storing billions of relationships and querying the graph with milliseconds latency.
What are use cases for Neptune?
For graph use cases such as recommendation engines, fraud detection, knowledge graphs, drug discovery, and network security.
What languages does Neptune support?
Amazon Neptune supports both the open source Apache TinkerPop Gremlin graph traversal language and the W3C standard Resource Description Framework’s (RDF) SPARQL query language.
Is Neptune ACID compliant?
Yes, Neptune is ACID compliant with immediate consistency.
Can I encrypt an existing decrypted Neptune database?
Currently, encrypting an existing unencrypted Neptune instance is not supported. To use Amazon Neptune encryption for an existing unencrypted database, create a new DB Instance with encryption enabled and migrate your data into it.
Does RDS support Oracle RAC?
No
What is UPSERT?
For Redshift, an UPSERT function allows us to either insert as a new record or update if a record of the same key already exists. Redshift can do this using a merge operation with a staging table.
How does RDS handle updates?
For RDS, certain OS updates are marked as Required. If you defer a required update, you receive a notice from Amazon RDS indicating when the update will be performed. Other updates are marked as Available, and these you can defer indefinitely. You can also apply the maintenance items immediately or schedule the maintenance for your next maintenance window.
How do you disable RDS backups?
Read Replicas require backups for managing read replica logs and thus you cannot set the retention period to 0. You must first remove the read replicas and then you can disable backups.
What is one way to save costs regarding Redshift backups?
There is no additional charge for backup storage up to 100% of your provisioned storage for an active data warehouse cluster. If you reduce to a 1-day retention period it can save costs.
