Connect to a PostgreSQL data source

You can use the PostgreSQL data source to query and visualize data from your Amazon Aurora PostgreSQL databases.

Adding the data source

Data source options

Min time interval

A lower limit for the $_interval $_interval_ms variables. Recommended to be set to write frequency, for example 1m if your data is written every minute. This option can also be overridden/configured in a dashboard panel under data source options. This value must be formatted as a number followed by a valid time identifier; for example, 1m (1 minute) or 30s (30 seconds). The following time identifiers are supported.

Database user permissions

The following example code shows creating a specifice PostgreSQL user with restricted permissions.

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

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

Query editor

You find the PostgreSQL query editor in the metrics tab in Graph or Singlestat panel’s edit mode. You enter edit mode by choosing the panel title, then edit.

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

Select table, time column, and metric column (FROM)

When you enter edit mode for the first time or add a new query, Grafana will try to prefill the query builder with the first table that has a timestamp column and a numeric column.

In the FROM field, Grafana will suggest tables that are in the search_path of the database user. To select a table or view not in your ,search_path you can manually enter a fully qualified name (schema.table) such as public.metrics.

The Time column field refers to the name of the column holding your time values. Selecting a value for the Metric column field is optional. If a value is selected, the Metric column field will be used as the series name.

The metric column suggestions will only contain columns with a text data type (char,varchar,text). To use a column with a different data type as metric column, you can enter the column name with a cast: ip::text. You can also enter arbitrary SQL expressions in the metric column field that evaluate to a text data type such as hostname || ' ' || container_name.

Columns, window, and aggregation functions (SELECT)

In the SELECT row, you can specify what columns and functions you want to use. In the column field, you can write arbitrary expressions instead of a column name such as column1 * column2 / column3.

The available functions in the query editor depend on the PostgreSQL version you selected when configuring the data source. If you use aggregate functions, you must group your result set. If you add an aggregate function, the editor will automatically add a GROUP BY time.

The editor tries to simplify and unify this part of the query.

You can add further value columns by choosing the plus button and selecting Column from the menu. Multiple value columns will be plotted as separate series in the graph panel.

Filtering data (WHERE)

To add a filter, choose the plus icon to the right of the WHERE condition. You can remove filters by choosing the filter and selecting Remove. A filter for the current selected time range is automatically added to new queries.

Group By

To group by time or any other columns choose the plus icon at the end of the GROUP BY row. The suggestion dropdown list will only show text columns of your currently selected table but you can manually enter any column. You can remove the group by choosing the item and then selecting Remove.

If you add any grouping, all selected columns must have an aggregate function applied. The query builder will automatically add aggregate functions to all columns without aggregate functions when you add groupings.

Gap filling

Amazon Managed Grafana can fill in missing values when you group by time. The time function accepts two arguments. The first argument is the time window that you want to group by, and the second argument is the value you want Grafana to fill missing items with.

Text editor mode (RAW)

You can switch to the raw query editor mode by choosing the hamburger icon and selecting Switch editor mode or by choosing Edit SQL below the query.

Macros

Macros can be used within a query to simplify syntax and allow for dynamic parts.

Table queries

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

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

Time series queries

If you set Format as to Time series, for use in a graph panel for example, the query must return a column named time that returns either a SQL datetime or any numeric data type representing Unix epoch. Any column except time and metric is treated as a value column. You can return a column named metric that is used as metric name for the value column. If you return multiple value columns and a column named metric, this column is used as prefix for the series name.

Result sets of time series queries must be sorted by time.

The following example code shows a metric column.

SELECT
  $__timeGroup("time_date_time",'5m'),
  min("value_double"),
  'min' as metric
FROM test_data
WHERE $__timeFilter("time_date_time")
GROUP BY time
ORDER BY time

The folowing code example shows using the fill parameter in the $__timeGroup macro to convert null values to be zero instead.

SELECT
  $__timeGroup("createdAt",'5m',0),
  sum(value) as value,
  measurement
FROM test_data
WHERE
  $__timeFilter("createdAt")
GROUP BY time, measurement
ORDER BY time

The following example code shows multiple columns.

SELECT
  $__timeGroup("time_date_time",'5m'),
  min("value_double") as "min_value",
  max("value_double") as "max_value"
FROM test_data
WHERE $__timeFilter("time_date_time")
GROUP BY time
ORDER BY time

Templating

Instead of hardcoding things such as server, application and sensor name in your metric queries you can use variables in their place. Variables are shown as dropdown select boxes at the top of the dashboard. You can use these dropdown boxes to change the data being displayed in your dashboard.

For more information about templating and template variables, see Templates.

Query variable

If you add a template variable of the type Query, you can write a PostgreSQL query that can return things such as 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 such as 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 following query 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

To use time range dependent macros such as $__timeFilter(column) in your query, the refresh mode of the template variable must be set to On Time Range Change.

SELECT event_name FROM event_log WHERE $__timeFilter(time_column)

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, the first value is used). The options in the dropdown list 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. Using a variable named region, you could have the hosts variable show only hosts from the current selected region. The following code example shows a query such as this (if region is a multi-value variable, use the IN comparison operator rather than = to match against multiple values).

SELECT hostname FROM host  WHERE region IN($region)

Using __searchFilter to filter results in Query Variable

Using __searchFilter in the query field will filter the query result based on what the user types in the dropdown select box. When nothing has been entered by the user, the default value for __searchFilter is %.

The following example shows how to use __searchFilter as part of the query field to enable searching for hostname while the user types in the dropdown select box.

SELECT hostname FROM my_host  WHERE hostname LIKE '$__searchFilter'

Using variables in queries

Template variable values are only quoted when the template variable is a multi-value.

If the variable is a multi-value variable, 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

Turning off quoting for multi-value variables

Amazon Managed Grafana automatically creates a quoted, comma-separated string for multi-value variables. For example: if server01 and server02 are selected then it will be formatted as: 'server01', 'server02'. To turn off quoting, use the csv formatting option for variables.

${servers:csv}

For more information about variable formatting options, see Templates and variables.

Annotations

Use annotations to overlay rich event information on top of graphs. You add annotation queries via the Dashboard menu / Annotations view. For more information, see Annotations.

The following example code shows a query using a time column with epoch values.

SELECT
  epoch_time as time,
  metric1 as text,
  concat_ws(', ', metric1::text, metric2::text) as tags
FROM
  public.test_data
WHERE
  $__unixEpochFilter(epoch_time)

The following example code shows a region query using time and timeend columns with epoch values.

SELECT
  epoch_time as time,
  epoch_time_end as timeend,
  metric1 as text,
  concat_ws(', ', metric1::text, metric2::text) as tags
FROM
  public.test_data
WHERE
  $__unixEpochFilter(epoch_time)

The following example code shows a query using a time column of native SQL date/time data type.

SELECT
  native_date_time as time,
  metric1 as text,
  concat_ws(', ', metric1::text, metric2::text) as tags
FROM
  public.test_data
WHERE
  $__timeFilter(native_date_time)

Alerting

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