Using PostgreSQL in Grafana

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

    Min time interval

    A lower limit for the and $__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. It’s important to note that this value needs to be formatted as a number followed by a valid time identifier, e.g. 1m (1 minute) or 30s (30 seconds). The following time identifiers are supported:

    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 recommend you create a specific PostgreSQL user with restricted permissions.

    Example:

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

    Query Editor

    [PostgreSQL - 图2

    ]()

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

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

    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) like 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 datatype (char,varchar,text). If you want to use a column with a different datatype as metric column you may enter the column name with a cast: ip::text. You may also enter arbitrary SQL expressions in the metric column field that evaluate to a text datatype like 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 may write arbitrary expressions instead of a column name like column1 * column2 / column3.

    The available functions in the query editor depend on the PostgreSQL version you selected when configuring the datasource. If you use aggregate functions you need to group your resultset. The editor will automatically add a GROUP BY time if you add an aggregate function.

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

    The above will generate the following PostgreSQL SELECT clause:

    1. avg(tx_bytes) OVER (ORDER BY "time" ROWS 5 PRECEDING) AS "tx_bytes"

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

    Filter data (WHERE)

    To add a filter click the plus icon to the right of the WHERE condition. You can remove filters by clicking on the filter and selecting Remove. A filter for the current selected timerange is automatically added to new queries.

    If you add any grouping, all selected columns need to 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

    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 would like 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 clicking the hamburger icon and selecting Switch editor mode or by clicking Edit SQL below the query.

    If you use the raw query editor, be sure your query at minimum has ORDER BY time and a filter on the returned time range.

    Macros

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

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

    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:

    PostgreSQL - 图4

    The query:

    2.   "user".login as "Created By",
    3.   dashboard.created as "Created On"
    4. FROM dashboard
    5. INNER JOIN "user" on "user".id = dashboard.created_by
    6. 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. Any column except time and metric are treated as a value column. You may 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 then this column is used as prefix for the series name (only available in Grafana 5.3+).

    Resultsets of time series queries need to be sorted by time.

    Example with metric column:

    1. SELECT
    2.   $__timeGroup("time_date_time",'5m'),
    3.   min("value_double"),
    4.   'min' as metric
    5. FROM test_data
    6. WHERE $__timeFilter("time_date_time")
    7. GROUP BY time
    8. ORDER BY time

    Example using the fill parameter in the $__timeGroup macro to convert null values to be zero instead:

    1. SELECT
    2.   $__timeGroup("createdAt",'5m',0),
    3.   sum(value) as value,
    4.   measurement
    5. FROM test_data
    6. WHERE
    7.   $__timeFilter("createdAt")
    8. GROUP BY time, measurement
    9. ORDER BY time

    Example with multiple columns:

    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.

    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.

    1. 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.

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

    To use time range dependent macros like $_timeFilter(column) in your query the refresh mode of the template variable needs to be set to _On Time Range Change.

    1. 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 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 as the text and id as the value:

      You can also create nested variables. Using a variable named region, 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):

      From Grafana 4.3.0 to 4.6.0, template variables are always quoted automatically. If your template variables are strings, do not wrap them in quotes in where clauses.

      From Grafana 4.7.0, template variable values are only quoted when the template variable is a multi-value.

      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:

      1. SELECT
      2.   atimestamp as time,
      3.   aint as value
      4. FROM table
      5. WHERE $__timeFilter(atimestamp) and hostname in($hostname)
      6. ORDER BY atimestamp ASC

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

      1. SELECT
      2.   atimestamp as time,
      3.   aint as value
      4. FROM table
      5. WHERE $__timeFilter(atimestamp) and hostname in([[hostname]])
      6. ORDER BY atimestamp ASC

      Disabling Quoting for Multi-value Variables

      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 disable quoting, use the csv formatting option for variables:

      ${servers:csv}

      Read more about variable formatting options in the Variables documentation.

      allow you to overlay rich event information on top of graphs. You add annotation queries via the Dashboard menu / Annotations view.

      Example query using time column with epoch values:

      1. SELECT
      2.   epoch_time as time,
      3.   metric1 as text,
      4.   concat_ws(', ', metric1::text, metric2::text) as tags
      5. FROM
      6.   public.test_data
      7. WHERE
      8.   $__unixEpochFilter(epoch_time)

      Example query using time column of native sql date/time data type:

      1. SELECT
      2.   native_date_time as time,
      3.   metric1 as text,
      4.   concat_ws(', ', metric1::text, metric2::text) as tags
      5. FROM
      6.   public.test_data
      7.   $__timeFilter(native_date_time)

      Alerting

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

      Configure the Datasource with Provisioning

      Here are some provisioning examples for this datasource.