Database package

Octave Forge

Official GNU/Octave Forge Database package supports only Postgres

• https://octave.sourceforge.io/database/index.html

3rd Party

On github/gitlab are several open source projects which supports different open source database solutions for GNU/Octave.

• sqlite
  • mex-sqlite3 – An extension for MATLAB® or GNU/octave to access sqlite3 databases
  • octave-sqlite - sqlite3 wrapper as an .oct file for GNU/Octave
  • [1] - MATLAB® native sqlite compatible extension for GNU/octave.
• redis
  • go-redis - mex file extension for GNU/Octave to access Redis
• MariaDB / MySQL
  • mex-mariadb - mex file extension for GNU/Octave to access MariaDB

Installation

This install guide covers the official (postgres) database package only.

Requires octave struct, libpq-dev, and liboctave-dev. In ubuntu/debian based systems this is handled with

apt install octave-struct libpq-dev liboctave-dev

And if you want postgres

apt install postgresql postgresql-client

Next octave command line:

>> pkg install -forge database

Can take a long time on low power devices. Packages are compiled. Monitor process with top.

Usage

Load it before any usage:

>> pkg load database

Connecting to a Database

The user running octave must have permissions to access the pg db, or you can pass the username and pass via pg_connect. Here is an example where the user has access to pg without passing credentials.

conn = pq_connect (setdbopts ("dbname", "mydatabase"));

Here, you are specifying a key-value pair. So you want to fill in a key (dbname), and that dbname is mydatabase.

Note: If you get an error similar to:

could not connect to server: No such file or directory
        Is the server running locally and accepting
        connections on Unix domain socket "/var/run/postgresql/.s.PGSQL.5432"?

Try connecting via the IP/port instead of the unix socket. e.g.

conn = pq_connect (setdbopts ("dbname", "testdatabase", "host", "localhost", "port", "5433", "user", "pguser", "password", "pguserpassword"))

Now, you are ready to read the db:

N = pq_exec_params (conn, "select * from Table1;")

Values are returned in a struct, e.g.:

 N =

  scalar structure containing the fields:

    data =
    {
      [1,1] = 3895
      [2,1] = 3942
      [3,1] = 3919
      [4,1] = 3866
      [5,1] = 3923
      [6,1] = 3969
      [1,2] = 1324612180367
      [2,2] = 1324612180369
      [3,2] = 1324612188073
      [4,2] = 1324612190313
      [5,2] = 1324612191841
      [6,2] = 1324612192922
    }
    columns =
    {
      [1,1] = value
      [1,2] = unixtime
    }
    types =

      1x2 struct array containing the fields:

        name
        is_array
        is_composite
        is_enum
        elements

Display specific elements e.g.:

display(N.data)

Convert to a format which can be plotted/graphed on an x,y axis:

p = cell2mat (N.data)

Graph:

plot (p(:, 2), p(:, 1))

Tips/Tricks

Cell2mat: Database Data Types Should be the Same

Note that you must have all database columns be the same type in order for the values to not get potentially changed when using cell2mat. In the example above, if you have the UnixTime column above be a bigint, and the Value column be an Int, the UnixTime will get truncated. Changing the Value column to a bigint will resolve this.

Built in Help Documentation

octave:1> database_doc()

Further Reading

• https://octave.sourceforge.io/database/index.html