PostgreSQL and relational databases

As well as assignment 4…

Reflections on relational DBs• Reasons for using a relational database

• Data fits nicely on one server and is used locally• We need absolute correctness for our data – remember, once

there is any error at all, we cannot provide a quantitative description of just how bad it might be

• We have a pile of programmers who know and love SQL• We need our queries/updates to be carefully vetted and stored for

security on the server, with no other queries/updates running• Our data is highly and repetitively structured• We need to heavily optimize our queries for very high volume

repetition• Our database will be fairly stable structurally and there is

downtime that can be used to make schema and mass data updates

• We don’t want to use two different database technologies and we already know we need a relational database for at least part of our data

• We want a db technology that is widely used and trusted and that is well understood by the software community as a whole

• We don’t want to risk using a db technology that might change or go away the day after tomorrow

PostgreSQL vs. MySQL

• PostgreSQL is a generation newer• It has nice UDT capabilities• There are libraries of UDTs that can be imported and used

• Both PostgreSQL and MySQL• Full text search• XML data types• To some degree free

• MySQL• Never underestimate the value of a heavily understood piece of

software• Lots of stacks and development environments come configured to

work with it (but to a lesser extent, this is true of PostgreSQL, too).

• It is a “core” SQL database, in that we can move pretty much to any other server-based DBMS is we start with MySQL

Installing PostgreSQL http://bitnami.org/stacks

http://bitnami.org/stack/wapp http://bitnami.org/stack/mapp

PostgreSQL install, continued Go to: http://127.0.0.1/phppgadmin/

Using PostgreSQL

Using PostgreSQL, continued

Assignment 4: Overview• You will build an application using PostgreSQL and Cassandra• The application will consist of a handful of operations that you

will perform on each database – you can run your operations manually and have no app

• PostgreSQL will hold your schema based, tabular data• But only the most recent data

• Cassandra will hold your schema-variable data and will be comprehensive over time• The operations you run on the Cassandra table will make

use of timestamps

• This is due at the beginning of class on Feb. 25.

Assignment 4: Tables• There will be two tables in PostgreSQL

• The first holds customers who are buying items• Key for customer, customer name, item purchased for each

row (FK of primary key of second table)• Note that will only keep the most recent purchase in the

table.• The second will hold the items for purchase

• Key for item; price for item; an overview of the item, which contains two fields, an item description and the market where the item is sold (U.S., Colorado, or something like that).

• Note we only keep the most recent price for each item.• Cassandra will hold the buying history of each customer

• What items purchased• How many of each item• Price paid all of the instances of a given item – prices can

change over time

Assignment 4: Operations http://

www.postgresql.org/docs/9.0/static/sql.html You will need to:

create 2 tables in PostgreSQL create a table in Cassandra search the Cassandra table by customer and

return the total amount spent to date for a given customer

search the Cassandra table by customer and return the price paid for a given item and the date it was bought; note that an item can be bought more than once and at different prices

create rows for tables in PostgreSQL, making sure to always replace a previous tuple if the primary key is already in the table

UDTs in PostgreSQL For extra credit, put a Two important

operators: Create domain

Does not support the making of complex types You can create an alias for a built-in data type and

specify the rang You can also specify a default value and null/not null.

Create Type Does not support nulls or default values

Either of them can be used to create enumerated types

A composite type contains more than one field

Example Create statementsCREATE DOMAIN addresss VARCHAR(50) NOT NULL

CREATE DOMAIN age INT CHECK (VALUE > 0 AND VALUE < 120)

Note: you can add check constraints to a create domain specification, but not to a type definition

CREATE TYPE addresses AS ( city VARCHAR(10), street VARCHAR(40), zip INTEGER)

Example insertsINSERT INTO people VALUES (‘t1', ‘wash car‘);

INSERT INTO myhobbies VALUES (myid, (“raise chickens”, “eat chickens”));

Postgis Geographic extensions for PostgreSQL http://postgis.net/windows_downloads Download 32 bit for windows Provides

Basic 2d types: points, lines, polygons, etc. Spatial operators: area, distance, etc. Some 3d support

Lets us ask questions like: do these two places overlap?

GIS

Assignment 5… Use the GIS database…..

Questions on midterm• The two books and the posted slides are important• No code writing• Questions will be conceptual, but each will have a specific answer• No essays or subjective material• We will review for the midterm on March 6• Example questions

• 1. You are going to build an application to manage the movement of energy on a grid. Of the db systems we have discussed in class, which would you use and why?

• 2. What is polyglot persistence?• 3. When we say there is a tradeoff between correctness and

speed (or throughput), what do we mean?• 4. What is a database “migration”?• 5. What is the difference between a key-value db and a key-

document db?• 6. Take the following relational table and put it in 1st normal form

(I would give you the attributes of the table, the PK, the FDs and the MVDs).