hasura/graphql-engine · error · AggregateBooleanExpressionError

the comparable relationship '{relationship_name}' for the op

Error message

the comparable relationship '{relationship_name}' for the operand type '{operand_type}' targets a command. This is not supported

What it means

Comparable relationships used for aggregation must target a model, not a command. If the resolved relationship target is a command, the resolver cannot build nested aggregate boolean expressions over it and throws this error.

Source

Thrown at v3/crates/metadata-resolve/src/stages/aggregate_boolean_expressions/types.rs:303

        boolean_expression_operand_type: QualifiedTypeName,
    },

    #[error(
        "the relationship '{relationship_name}' is defined more than once in the comparable relationships"
    )]
    DuplicateComparableRelationshipsFound {
        relationship_name: open_dds::relationships::RelationshipName,
    },

    #[error(
        "the comparable relationship '{relationship_name}' was not found for the operand type '{operand_type}'"
    )]
    ComparableRelationshipNotFound {
        operand_type: Qualified<CustomTypeName>,
        relationship_name: RelationshipName,
    },

    #[error(
        "the comparable relationship '{relationship_name}' for the operand type '{operand_type}' targets a command. This is not supported"
    )]
    ComparableRelationshipCommandTargetNotSupported {
        operand_type: Qualified<CustomTypeName>,
        relationship_name: RelationshipName,
    },

    #[error(
        "the comparable relationship '{relationship_name}' for the operand type '{operand_type}' is an array relationship. This is not supported"
    )]
    ComparableArrayRelationshipNotSupported {
        operand_type: Qualified<CustomTypeName>,
        relationship_name: RelationshipName,
    },

    #[error(
        "the comparable relationship '{relationship_name}' for the operand type '{operand_type}' targets a model than cannot be found: '{target_model_name}'"
    )]

View on GitHub (pinned to 724551b9ae)

Solutions

1. Remove the command-targeting relationship from comparableRelationships
2. If aggregation support is needed, create a model-based relationship targeting the same underlying data and use that instead
3. Restructure the command as a model if it must support aggregate boolean expressions

Example fix

# before
relationships:
  - name: topPosts
    target: { command: { name: TopPosts } }
comparableRelationships:
  - relationshipName: topPosts

# after
comparableRelationships:
  - relationshipName: posts   # relationship targeting a model

for r in &comparable_relationships {
    let target = operand_type.relationships[&r.relationship_name].target();
    assert!(target.is_model(), "command-targeting relationship cannot be comparable");
}

When it happens

Trigger: Declaring a relationship whose target is a command as a comparable relationship in an aggregate boolean expression type's metadata.

Common situations: Using command-based relationships (e.g. relationships backed by a custom query/command) and assuming they support aggregation filters; migrating from model targets to command targets without removing them from comparable relationships.

Related errors

• the type of the comparable field '{field_name}' ({field_type
• the boolean expression type ({boolean_expression_type}) used
• the comparable relationship '{relationship_name}' for the op
• Condition {condition_hash} not found
• could not find a scalar-operanded boolean expression type na

AI-assisted analysis of hasura/graphql-engine@724551b9ae (2026-08-28). Data as JSON: /api/errors/42175f4dbbf39fdb. Report an issue: GitHub.