How to calculate A * B mod N, where numbers are 64 bit integers

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:


Citus with multi-coordinator using Streaming Replication

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.



When should I do VACUUM FULL?

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