Motivation

There is a hobby I always want to develop but never gets into practice: watch lecture videos while I eat. The reason because lecture videos are mostly not fun especially when the content of the video is entirely new to you. However, this semester I want to actually start developing this habbit partly because I'm missing system side of computer science. I miss the database knowledge I have picked up in the past three years and I don't want to lose the touch in this field. So, I think why not start to watch database lecture videoes for fun when I eat? That leads to this post.

This post is a log of cool points I like when I watch CMU Database Group Database Systems lecture video.

Log

--- 09/07/2017 UPDATE ---

• There are bunch of data models besides relational model: relational, key/value, graph, document, column-family, array/matrix, hierarchical, network

• Thanks to Prof.Andy Pavlo, I finally understand the difference between relational algebra and relational calculus in terms of their purpose:

  When we talk about using data manipulation language (DML) to store and retrieve information from a database, there are two categories: procedural and non-procedural, which corresponds to relational algebra and relational calculus respectively. For procedural language, the query specifies the (high-level) strategy the DBMS should use to find the desired result. For non-procedural lanaguages, the query specifies only what data is wanted and not how to find it. In fact, SQL is derived from relational calculus. In other words, relational calculus is used when we try to come up with a different query language to replace SQL.

• The fundamental operators in relational algebra need to be implemented in the database system in order to manipulate tuples: \(\sigma \text{(select)}, \pi \text{(projection)}, \cup \text{(union)}, \cap \text{(intersection)}, - \text{(difference)}, \times \text{(product)}, \bowtie \text{(join)}\).

--- 11/14/2018 UPDATE ---

• Lock vs. Latch in database context:

  • Lock is a high-level primitive on a logical component of a database: a lock on a database, a lock on a table, a lock on a record
  • Latch is the lock from OS perspective (a low-level primitive that works on the data structure): a latch on the page table, a latch on a index page