Picking random element, with weights

Whenever I'm doing some testing I need sample data. Easiest way to do it is to generate data using some random/generate_series queries.

But what if I need specific frequencies?

For example, I need to generate 10,000,000 rows, where there will be 10% of ‘a', 20% of ‘b', and the rest will be split equally between ‘c' and ‘d'?

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Starting with Pg – where/how can I set configuration parameters?

Previously I wrote about locating config files.

The thing is – postgresql.conf is not the only place you can set your configuration in.

In here, I'll describe all the places that can be used, why do we even have more than one place, and finally – how to find out where given value comes from.

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Starting with Pg – where is the config?

Over the years I saw some people find themselves in position where they have to start dealing with PostgreSQL with minimal, or none, prior exposure. This leads to problems with seemingly easy tasks – how to change config? How to find stuff in logs?

So I decided to write some blogposts to be able to point such people to pre-made tutorials.

And I start today, with information on how to find PostgreSQL config files.

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How to install and configure PostgreSQL Debian/Ubuntu – for developer use – part 2

In previous post I showed how I'd install PostgreSQL for developer.

But that's not all. Now we need to add some configuration. What, how, where?

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How to install and configure PostgreSQL Debian/Ubuntu – for developer use – part 1

Recently I spent some time thinking about what can be improved when it comes to helping new users start using PostgreSQL.

One thing that almost immediately jumped to my mind is – how to install PostgreSQL? The task is theoretically simple. But there are always some caveats – which packages to use, what to configure in the beginning, where to find config files and logs.

With that in mind I decided to write a howto based on my ideas on what is right. These do not necessarily mean that these are the best for everybody, but I think this is a good start for anyone wanting to start their adventure with PostgreSQL.

Final note of warning – this post is for installing and setting PostgreSQL on developer workstation. As in: server where user can do anything, and we don't really care about security. Please do not configure production servers using this howto.

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How to run short ALTER TABLE without long locking concurrent queries

Recently I've seen case like:

  1. application had to add column to table.
  2. application ran ALTER TABLE ADD COLUMN (without default!)
  3. everything stopped for many MINUTES

Why? How to avoid the problem?

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