Читать книгу Official Google Cloud Certified Professional Data Engineer Study Guide - Dan Sullivan - Страница 54

Know the four stages of the data lifecycle: ingest, storage, process and analyze, and explore and visualize. Ingestion is the process of bringing application data, streaming data, and batch data into the cloud. The storage stage focuses on persisting data to an appropriate storage system. Processing and analyzing is about transforming data into a form suitable for analysis. Exploring and visualizing focuses on testing hypotheses and drawing insights from data.

Understand the characteristics of streaming data. Streaming data is a set of data that is sent in small messages that are transmitted continuously from the data source. Streaming data may be telemetry data, which is data generated at regular intervals, and event data, which is data generated in response to a particular event. Stream ingestion services need to deal with potentially late and missing data. Streaming data is often ingested using Cloud Pub/Sub.

Understand the characteristics of batch data. Batch data is ingested in bulk, typically in files. Examples of batch data ingestion include uploading files of data exported from one application to be processed by another. Both batch and streaming data can be transformed and processed using Cloud Dataflow.

Know the technical factors to consider when choosing a data store. These factors include the volume and velocity of data, the type of structure of the data, access control requirements, and data access patterns.

Know the three levels of structure of data. These levels are structured, semi-structured, and unstructured. Structured data has a fixed schema, such as a relational database table. Semi-structured data has a schema that can vary; the schema is stored with data. Unstructured data does not have a structure used to determine how to store data.

Know which Google Cloud storage services are used with the different structure types. Structured data is stored in Cloud SQL and Cloud Spanner if it is used with a transaction processing system; BigQuery is used for analytical applications of structured data. Semi-structured data is stored in Cloud Datastore if data access requires full indexing; otherwise, it can be stored in Bigtable. Unstructured data is stored in Cloud Storage.

Know the difference between relational and NoSQL databases. Relational databases are used for structured data whereas NoSQL databases are used for semi-structured data. The four types of NoSQL databases are key-value, document, wide-column, and graph databases.