How to handle Grafana "All" option with QuestDB without expanding all variable values?

Question

I'm using Grafana with QuestDB and have a multi-value variable element with "All" option enabled. When "All" is selected, Grafana expands all values in the WHERE clause:

-- Current behavior when "All" is selected:
AND element IN ('value1', 'value2', 'value3', ... 'value1000')  -- Performance issue

This causes very long queries and performance problems with large datasets.

I want to skip the filter entirely or use a more efficient approach when "All" is selected, instead of listing every value. I've tried: Complex conditional logic checking for magic values, but it feels hacky:

AND (
    ${element} = '_ALL_GRAFANA_MAGIC_'
    AND element IS NOT NULL AND element <> '' OR
    (
        ${element:sqlstring} != '_ALL_GRAFANA_MAGIC_' 
        AND element IN ('${element}') 
    )
)

What's the best practice to handle Grafana's "All" option with QuestDB queries efficiently?

William F. Jameson · Accepted Answer · 2025-08-14 14:12:24Z

1

The cleanest approach is to use Grafana's built-in variable behavior:

SELECT * FROM your_table
WHERE 
  $__timeFilter(timestamp)
  AND (
    '$element' = '__all_values__' 
    OR element IN ($element)
  )

When "All" is selected, Grafana sets the variable to __all_values__, so the first condition becomes true and the IN clause is ignored due to SQL's short-circuit evaluation.

answered Aug 14 at 14:12

William F. Jameson

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