Using PostgreSQL in Grafana

Grafana ships with a built-in PostgreSQL data source plugin that allows you to query and visualize data from a PostgreSQL compatible database.

Adding the data source

  1. Open the side menu by clicking the Grafana icon in the top header.
  2. In the side menu under the Dashboards link you should find a link named Data Sources.
  3. Click the + Add data source button in the top header.
  4. Select PostgreSQL from the Type dropdown.

Database User Permissions (Important!)

The database user you specify when you add the data source should only be granted SELECT permissions on the specified database & tables you want to query. Grafana does not validate that the query is safe. The query could include any SQL statement. For example, statements like DELETE FROM user; and DROP TABLE user; would be executed. To protect against this we Highly recommmend you create a specific postgresql user with restricted permissions.

Example:

 CREATE USER grafanareader WITH PASSWORD 'password';
 GRANT USAGE ON SCHEMA schema TO grafanareader;
 GRANT SELECT ON schema.table TO grafanareader;

Make sure the user does not get any unwanted privileges from the public role.

Macros

To simplify syntax and to allow for dynamic parts, like date range filters, the query can contain macros.

Macro exampleDescription
$__time(dateColumn)Will be replaced by an expression to rename the column to time. For example, dateColumn as time
$__timeSec(dateColumn)Will be replaced by an expression to rename the column to time and converting the value to unix timestamp. For example, extract(epoch from dateColumn) as time
$__timeFilter(dateColumn)Will be replaced by a time range filter using the specified column name. For example, dateColumn > to_timestamp(1494410783) AND dateColumn < to_timestamp(1494497183)
$__timeFrom()Will be replaced by the start of the currently active time selection. For example, to_timestamp(1494410783)
$__timeTo()Will be replaced by the end of the currently active time selection. For example, to_timestamp(1494497183)
$__timeGroup(dateColumn,‘5m’)Will be replaced by an expression usable in GROUP BY clause. For example, (extract(epoch from “dateColumn”)/extract(epoch from ‘5m’::interval))::int
$__unixEpochFilter(dateColumn)Will be replaced by a time range filter using the specified column name with times represented as unix timestamp. For example, dateColumn > 1494410783 AND dateColumn < 1494497183
$__unixEpochFrom()Will be replaced by the start of the currently active time selection as unix timestamp. For example, 1494410783
$__unixEpochTo()Will be replaced by the end of the currently active time selection as unix timestamp. For example, 1494497183

We plan to add many more macros. If you have suggestions for what macros you would like to see, please open an issue in our GitHub repo.

The query editor has a link named Generated SQL that shows up after a query as been executed, while in panel edit mode. Click on it and it will expand and show the raw interpolated SQL string that was executed.

Table queries

If the Format as query option is set to Table then you can basically do any type of SQL query. The table panel will automatically show the results of whatever columns & rows your query returns.

Query editor with example query:

The query:

SELECT
  title as "Title",
  "user".login as "Created By",
  dashboard.created as "Created On"
FROM dashboard
INNER JOIN "user" on "user".id = dashboard.created_by
WHERE $__timeFilter(dashboard.created)

You can control the name of the Table panel columns by using regular as SQL column selection syntax.

The resulting table panel:

Time series queries

If you set Format as to Time series, for use in Graph panel for example, then the query must return a column named time that returns either a sql datetime or any numeric datatype representing unix epoch in seconds. Any column except time and metric is treated as a value column. You may return a column named metric that is used as metric name for the value column.

Example with metric column

SELECT
  min(time_date_time) as time,
  min(value_double),
  'min' as metric
FROM test_data
WHERE $__timeFilter(time_date_time)
GROUP BY metric1, (extract(epoch from time_date_time)/extract(epoch from $__interval::interval))::int
ORDER BY time asc

Example with multiple columns:

SELECT
  min(time_date_time) as time,
  min(value_double) as min_value,
  max(value_double) as max_value
FROM test_data
WHERE $__timeFilter(time_date_time)
GROUP BY metric1, (extract(epoch from time_date_time)/extract(epoch from $__interval::interval))::int
ORDER BY time asc

Templating

Instead of hard-coding things like server, application and sensor name in you metric queries you can use variables in their place. Variables are shown as dropdown select boxes at the top of the dashboard. These dropdowns makes it easy to change the data being displayed in your dashboard.

Checkout the Templating documentation for an introduction to the templating feature and the different types of template variables.

Query Variable

If you add a template variable of the type Query, you can write a PostgreSQL query that can return things like measurement names, key names or key values that are shown as a dropdown select box.

For example, you can have a variable that contains all values for the hostname column in a table if you specify a query like this in the templating variable Query setting.

SELECT hostname FROM host

A query can return multiple columns and Grafana will automatically create a list from them. For example, the query below will return a list with values from hostname and hostname2.

SELECT host.hostname, other_host.hostname2 FROM host JOIN other_host ON host.city = other_host.city

Another option is a query that can create a key/value variable. The query should return two columns that are named __text and __value. The __text column value should be unique (if it is not unique then the first value is used). The options in the dropdown will have a text and value that allows you to have a friendly name as text and an id as the value. An example query with hostname as the text and id as the value:

SELECT hostname AS __text, id AS __value FROM host

You can also create nested variables. For example if you had another variable named region. Then you could have the hosts variable only show hosts from the current selected region with a query like this (if region is a multi-value variable then use the IN comparison operator rather than = to match against multiple values):

SELECT hostname FROM host  WHERE region IN($region)

Using Variables in Queries

Template variables are quoted automatically so if it is a string value do not wrap them in quotes in where clauses. If the variable is a multi-value variable then use the IN comparison operator rather than = to match against multiple values.

There are two syntaxes:

$<varname> Example with a template variable named hostname:

SELECT
  atimestamp as time,
  aint as value
FROM table
WHERE $__timeFilter(atimestamp) and hostname in($hostname)
ORDER BY atimestamp ASC

[[varname]] Example with a template variable named hostname:

SELECT
  atimestamp as time,
  aint as value
FROM table
WHERE $__timeFilter(atimestamp) and hostname in([[hostname]])
ORDER BY atimestamp ASC

Alerting

Time series queries should work in alerting conditions. Table formatted queries is not yet supported in alert rule conditions.