July 2009
Beginner to intermediate
384 pages
12h 56m
English
Content preview from Beautiful Data
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Complex Queries
As web applications become more complex and interesting, they need to retrieve and combine information from the database in new and different ways. Next, we examine how to support those queries at a massive scale.
The Challenge
Our system is optimized for queries that touch one or just a few records. In particular, we can look up records by primary key; once we know Alice's username, it is straightforward to determine which partition contains her profile record and read it while loading her page. Also, our system can store data as hash-partitioned or range-partitioned tables. For range-partitioned tables, we can conduct range scans over ordered ranges of primary keys. For example, we might store Alice's friends list by having one record per connection, where the primary key of each connection is the pair of user IDs for Alice and the friend (Table 4-7).
Table 4-7. Friends table
User1 | User2 | … |
|---|---|---|
Alice | Bob | … |
Alice | Charles | … |
Alice | Dave | … |
… | ||
In a range-partitioned table, all of the records prefixed with "Alice" will be clustered, and a short-range scan will be able to pick them up.
Now imagine that we want to add another feature to our social network site. Users can post photos and then comment on one another's photos. Alice might comment on Bob's photo, Charles's photo, and Dave's photo. When we display a photo, we want to show the set of comments associated with that photo. We also want to show Alice the set of comments she has made on other people's photos. We specify the primary key of ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.