I made a program to calculate ‘A * B mod N’, where A, B and N are 64 bit integers.

Main problem is to avoid overflow when calculate ‘A * B’.

I searched a while and finally decided to use the interleaved modular multiplication method, which is used in the feild of electric circuit design.

I found some bugs when I tested corner cases, so I have to fix them [2018.9.2]. I think I’ve fixed them [2018.9.3]. I’ve just improved it! [2018.9.5]

The program is shown below:

In the standard setup of Citus, it has one coordinator, so it is the single point of failure and the bottle neck of the system.

To solve these disadvantages, I built a multi-coordinator using Streaming Replication, which is the built-in replication feature of PostgreSQL.

There is unfortunately no best practice when you should execute “VACUUM FULL”. The extension pg_freespacemap however gives you suggestion.

At the end of 2014, I was shocked at the progress of blind deblurring algorithm, so I studied the recent researches in this field.

I read many papers and made a system based on this paper: “Blind deconvolution using alternating maximum a posteriori estimation with heavy-tailed priors”.

I always use my customized statistics views shown below because the original ones provide only minimum information.

I show my tools in this post.

Many people around the world admire the Uber’s article “Why Uber Engineering Switched from Postgres to MySQL”, but I think this article contains many mistakes.

So, I’m going to provide correct information regarding to PostgreSQL and MySQL.

In this post, I explain the replication of both databases.

I made a CentOS vagrant box which contains GNOME desktop environment, so I will show how to use and to make it.

I found an interesting quiz about PLpgSQL.

Five years ago, I was interested in Postgres-XC , currenty called Postgres-X2, and made a multi-GTM (global transaction manager) system for it.

Though I had forgotten this work for a long time, I found its executable files from my old PC a month ago (unfortunately the source code of them was lost). They perfectly run, so I provide a Vagrant box to run my old program on your PC.

I’ll demonstrate how to relocate a tablespace directory without the reconstruction of databases.