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The Art of PostgreSQL

Introduction to Data Manipulation and Concurrency Control

Get an introduction to data manipulation and concurrency control.

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Tweets dataset

We used a dataset of 200,000 USA-geolocated Tweets with a very simple data model. The data model is a direct port of the Excel sheet format, allowing a straightforward loading process—we used the \copy command from the psql tool.

PostgreSQL
begin;
create table tweet
 (
   id         bigint primary key,
   date       date,
   hour       time,
   uname      text,
   nickname   text,
   bio        text,
   message    text,
   favs       bigint,
   rts        bigint,
   latitude   double precision,
   longitude  double precision,
   country    text,
   place      text,
   picture    text,
   followers  bigint,
   following  bigint,
   listed     bigint,
   lang       text,
   url        text
 );
\copy tweet from '/usercode/tweets.csv' with csv header delimiter ';'
commit;

Database model and normalization

The tweets.sql database model is all wrong per the normal forms introduced earlier:

  • There’s neither a unique constraint nor a primary key, so there is nothing preventing the insertion of duplicate entries, violating 1NF.

  • Some non-key attributes are not dependent on the key because we mix data from the Twitter account posting the message and the message itself, violating ...