View source for Data set

{{DISPLAYTITLE:data_set_t}}
The '''data_set_t''' structure describes a value being passed around in ''collectd''. It serves a similar purpose as a ''schema'' in relational databases and describes the data contained in a [[value_list_t]] structure. The '''type''' field in the ''value list'' is used to refer to one specific ''data set''. The two terms, “data set” and “type”, are often used interchangeably in the documentation.

The following information is stored in this structure:

* A ''type'' (a name), by which this struct is uniquely identified.
* One of more [[data source]]s, where each data source contains:
** The name of the data source. If there is only one data source, this name is usually “value”.
** The type of the data source, i.&nbsp;e. one of <code>[[Counter|DS_TYPE_COUNTER]]</code>, <code>[[Gauge|DS_TYPE_GAUGE]]</code>, <code>[[Derive|DS_TYPE_DERIVE]]</code>, and <code>[[Absolute|DS_TYPE_ABSOLUTE]]</code>.
** A minimum and a maximum value, both of which may be ''NaN'' (not a number).

== Definition of the struct ==

The structure is defined in {{GitFile|src/plugin.h}} as follows:

<source lang="c">
 struct data_source_s
 {
   char   name[DATA_MAX_NAME_LEN];
   int    type;
   double min;
   double max;
 };
 typedef struct data_source_s data_source_t;
 
 struct data_set_s
 {
   char           type[DATA_MAX_NAME_LEN];
   int            ds_num;
   data_source_t *ds;
 };
 typedef struct data_set_s data_set_t;
</source>

== Definition of new types ==

Types are defined in a configuration file called ''types.db''. See the {{Manpage|types.db|5}} manual page for details.

== Look-up ==

The data set can be queried from the daemon using the <code>plugin_get_ds</code> function declared in {{GitFile|src/plugin.h}}. The ''type'' member of a [[value_list_t]] can be used for this.

[[Category:Development]]