Database package: Difference between revisions
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** [https://github.com/rmartinjak/mex-sqlite3 mex-sqlite3] – An extension for MATLAB® or GNU/octave to access sqlite3 databases | ** [https://github.com/rmartinjak/mex-sqlite3 mex-sqlite3] – An extension for MATLAB® or GNU/octave to access sqlite3 databases | ||
** [https://github.com/Andy1978/octave-sqlite octave-sqlite] - sqlite3 wrapper as an .oct file for GNU/Octave | ** [https://github.com/Andy1978/octave-sqlite octave-sqlite] - sqlite3 wrapper as an .oct file for GNU/Octave | ||
** [https://gnu-octave.github.io/octave-sqlite/ sqlite] - MATLAB® native sqlite compatible extension for GNU/octave. | |||
* '''redis''' | * '''redis''' | ||
** [https://gitlab.com/markuman/go-redis go-redis] - mex file extension for GNU/Octave to access Redis | ** [https://gitlab.com/markuman/go-redis go-redis] - mex file extension for GNU/Octave to access Redis | ||
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==Installation== | ==Installation== | ||
Requires octave struct. In ubuntu/debian based systems this is handled with | <small>This install guide covers the official (postgres) database package only.</small> | ||
apt install octave-struct | |||
Requires octave struct, libpq-dev, and liboctave-dev. In ubuntu/debian based systems this is handled with | |||
apt install | apt install octave-struct libpq-dev liboctave-dev | ||
And if you want postgres | |||
apt install postgresql postgresql-client | |||
Next octave command line: | Next octave command line: | ||
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>> pkg install -forge database | >> pkg install -forge database | ||
Packages are compiled. Monitor process with top. | Can take a long time on low power devices. Packages are compiled. Monitor process with top. | ||
==Usage== | ==Usage== | ||
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===Connecting to a 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: | |||
<pre>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"? | |||
</pre> | |||
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.: | |||
<pre> | |||
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 | |||
</pre> | |||
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== | ==Further Reading== |