RustProof Labs: blogging for education (logo)

From Idea to Database: Define, Design, Repeat

By Ryan Lambert -- Published September 07, 2018

The database is one of the most critical components of most software projects. Planning for your database project should not be taken lightly. Failure rates in IT projects are unfortunately high; much of that problem is due to a lack of proper planning and design. Most of the database anti-patterns I previously wrote about can be avoided by understanding the system you need to build and designing it appropriately.

This post uses the PiWS project to illustrate the Define and Design approach I use throughout the initial development phases of any new database project. Most projects go through multiple iterations of define and design.

This post is part of the series PostgreSQL: From Idea to Database. This series uses the PiWS project for our example project, to read more about the PiWS, see my introductory post.

Project management, not optional

Anyone who has worked on a project with more than one person to design and build anything has heard this: "I forgot to tell you..." followed by some various change requirements.

Continue Reading

Gotcha restoring XML data from pg_dump

By Ryan Lambert -- Published August 25, 2018

Recently, I ran into a problem when moving a database from a production PostGIS-enabled PostgreSQL database to a local development virtual machine. This database includes a table many QGIS users may have encountered: public.layer_styles. The public.layer_styles table is used by QGIS software to allow saving the styling used for PostGIS spatial layers. Style information is stored in XML format in a column named styleqml that includes a document type declaration (<!DOCTYPE>).

XML data with <!DOCTYPE> is at the core of this problem. If your PostGIS databases uses the public.layer_styles table, the workaround and other considerations will be helpful.

The bug: Invalid pg_dump file w/ XML

The problem encountered is filed under bug #15342. I like how Tom Lane summarized the issue:

"There are two problems here: pg_dump neglects to force a safe value of xmloption for the restore step, plus there doesn't seem to be a safe value for it to force :-(."

The rest of this post explores the factors involved with this problem.

Who does this affect?

If you have a PostGIS database with QGIS users storing style information in the public.layer_styles table, you are affected. More specifically, this affects PostgreSQL databases with columns using the XML data type storing XML data that includes <!DOCTYPE> blocks. These databases will experience headaches when restoring dump files saved using the pg_dump or pg_dumpall utilities.

The Check for XML columns section below provides a query to help determine if your databases are affected.

Continue Reading

PostgreSQL Crash Course

By Ryan Lambert -- Published July 30, 2018

PostgreSQL is a powerful, open-source relational database (RMDS). It is the database of choice here at RustProof Labs, I wrote previously why I chose PostgreSQL over MySQL. This post provides a 10-mile view of how PostgreSQL is structured, tools to use, and other important concepts. The goal is to provide a broad view of PostgreSQL with resources to more detail on each topic, without getting caught up in too much technical jargon.

This post is part of the series PostgreSQL: From Idea to Database.

Installing PostgreSQL

PostgreSQL will run on most any modern hardware and operating systems. PostgreSQL has installation guides for a large number of operating systems, supporting most Linux/Unix, Mac, and Windows. As for hardware, it will run on nearly anything modern, including a Raspberry Pi (ARM processor). See the PostgreSQL supported platforms for more details.

I have ran PostgreSQL on Linux servers of all sizes, from tiny to powerful. I previously wrote about load testing PostgreSQL that gives more detail about some of the systems it can run on and what type of performance to expect.

PostgreSQL Structure

Every RDMS has its own way to organize the elements required for a reliable database system. PostgreSQL has the following hierarchy to organize the required elements.

Cluster > Database > Schema > Table > Data

Data is stored as rows, contained in tables, within a schema, within a database, within a cluster. The PostgreSQL Concepts page provides a nice explanation of this overall structure.

Continue Reading

Security is a feature. Choose it!

By Ryan Lambert -- Published July 11, 2018

Nearly every modern organization, large or small, has a significant amount of IT infrastructure reliant on 3rd parties. For the purpose of this post, 3rd parties includes anything you think of as "the cloud" (e.g. not my servers) or any service that you don't fully control on your hardware. Web hosting, email, social media, and file storage are all examples of services commonly outsourced.

I wrote previously about the responsibilities associated with managing data securely. A solid cybersecurity posture should require evaluating 3rd parties for proper security practices. This post provides a loose framework for evaluating a 3rd party's overall cybersecurity posture. This evaluation can then be used in your ongoing decision making to pick new vendors and reevaluate existing vendors. This post does not go in depth to any specific technology or vendor specific details, instead I intend to focus more on the culture of security.

Security as a feature

Security as a feature in this model has 3 overarching components:

  • Preparation
  • Problem solving
  • Learn from mistakes

The quality of cybersecurity is an aggregate of these three components. An organization with good security practices is well prepared, knows how to react when something goes wrong, and they learn from their mistakes.

Plan for the worst, hope for the best.

The reality is, until more organizations make cybersecurity a higher priority, the never-ending stream of data breaches will continue.

Continue Reading

PostGIS: Tame your spatial data (Part 1)

By Ryan Lambert -- Published July 06, 2018

The goal of this post is to examine and fix one common headache when using spatial data: its size. Spatial data (commonly called "GIS data") can become painfully slow because spatial data gets big in a hurry. I discussed this concept before by reducing the OSM roads layer to provide low-overhead thematic layers. This post uses the same basic philosophy to reduce another common bottleneck with polygon layers covering large areas, such as the US county boundaries.

This post goes into detail about using PostGIS to simplify large polygon objects, the effects this has on storage, performance and the accuracy of spatial analysis when using simplified geometries. The solution provided is not suitable for all data and/or use cases, particularly if a high level of accuracy and precision is required.

One of the main reasons why PostgreSQL became my personal favorite RDMS was its PostGIS extension, providing the most robust spatial database in the world.

This post is an advanced topic of the series PostgreSQL: From Idea to Database.

A numeric example

This post assumes basic knowledge of SQL syntax, PostgreSQL and PostGIS.

To begin this conversation, let's examine a bit about what we already know about storing numbers. Let's start with Pi (π). Pi is a mathematical constant, roughly represented as 3.14159, though the decimals go on and on into infinity. The following example shows how to create a table with a single row storing two different representations of Pi. The first column, pi_long, stores 31 decimals of Pi. The pi_short column stores only two decimal places.

DROP TABLE IF EXISTS cool_numbers;
CREATE TEMP TABLE cool_numbers AS 
SELECT 3.1415926535897932384626433832795::NUMERIC(32,31) AS pi_long,
    3.14::NUMERIC(3,2) AS pi_short;

As you may expect, storing a number with more digits takes more disk space than storing a number with fewer digits. This is called precision. The following query uses the pg_column_size() function to illustrate that the number with more decimal spaces takes up more disk space.

Continue Reading

<-- Older Posts          Newer Posts -->