kestra-io/kestra · error · PebbleException

Could not perform greater than comparison

Error message

Could not perform greater than comparison

What it means

Thrown by the custom GreaterThanExpression Pebble node when the '>' comparison fails. Like its '>=' counterpart, it first attempts string comparison, then delegates to OperatorUtils.gt. If the numeric comparison throws because the operands are incomparable types, the error is wrapped with this message.

Solutions

1. Verify both sides of '>' resolve to mutually comparable types (both strings or both numbers).
2. Use a null-coalescing default: '{{ (outputs.task.value ?? 0) > threshold }}'.
3. Cast or parse the operand to a known numeric type before comparing.

Example fix

{# before #}
{% if outputs.task.value > limit %}

{# after #}
{% if (outputs.task.value ?? 0) > (limit ?? 0) %}

{# Default both sides to a numeric value before using > #}
{% set left = (vars.value ?? 0) %}
{% set right = (vars.limit ?? 0) %}
{% if left > right %}...{% endif %}

{# Guard against null or complex types before comparing #}
{% set safe_val = outputs.task.value ?? 0 %}
{% if safe_val is not null and safe_val is not iterable %}
  {{ safe_val > 0 }}
{% endif %}

When it happens

Trigger: Using '>' between non-comparable types in a Pebble expression: '{{ mymap > 0 }}', '{{ null > 1 }}', '{{ somelist > 5 }}'. Also when one operand resolves to a boolean or complex type at runtime.

Common situations: Conditionals in flow templates that compare dynamically-typed outputs. A task output whose type varies between runs (sometimes a number, sometimes an object). Comparing dates represented as strings without first converting them to date types — note string comparison does work but lexicographic ordering may give unexpected results.

Related errors

• Could not perform greater than or equals comparison
• Could not perform less than comparisonPebb
• Could not perform less than or equals comparison
• Cannot concat with
• 'chunk' filter argument 'size' must be a number. Actual…

AI-assisted analysis of kestra-io/kestra@823fada927 (2026-08-14). Data as JSON: /api/errors/5dd7694c008ac0d1. Report an issue: GitHub.

Appendix: source

Thrown at core/src/main/java/io/kestra/core/runners/pebble/expression/GreaterThanExpression.java:24

import io.pebbletemplates.pebble.template.PebbleTemplateImpl;
import io.pebbletemplates.pebble.utils.OperatorUtils;

public class GreaterThanExpression extends BinaryExpression<Boolean> {
    @Override
    public Boolean evaluate(PebbleTemplateImpl self, EvaluationContextImpl context) {
        Object left = this.getLeftExpression().evaluate(self, context);
        Object right = this.getRightExpression().evaluate(self, context);

        // add support for string comparison
        if (left instanceof String sLeft && right instanceof String sRight) {
            return sLeft.compareTo(sRight) > 0;
        }

        // default implementation from io.pebbletemplates.pebble.node.expression.GreaterThanExpression
        try {
            return OperatorUtils.gt(left, right);
        } catch (Exception ex) {
            throw new PebbleException(
                ex, "Could not perform greater than comparison", this.getLineNumber(), self
                    .getName()
            );
        }
    }
}

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