hasura/graphql-engine · error · BooleanExpressionIssue::MultidimensionalArrayComparableFieldNotSupported

the type of the comparable field '{field_name}' on the boole

Error message

the type of the comparable field '{field_name}' on the boolean expresssion '{boolean_expression_type_name}' is a multidimensional array type: {field_type}. Multidimensional arrays are not supported in boolean expressions

What it means

A comparable field's type resolves to a multidimensional array (array of arrays). Multidimensional arrays cannot be expressed in boolean expression filters, so resolution fails outright.

Source

Thrown at v3/crates/metadata-resolve/src/stages/boolean_expressions/types.rs:67

        name: FieldName,
    },
    #[error(
        "the comparable relationship '{name}' is defined more than once in the boolean expression type '{type_name}'"
    )]
    DuplicateComparableRelationshipFound {
        type_name: Qualified<CustomTypeName>,
        name: RelationshipName,
    },
    #[error(
        "the boolean expression '{type_name}' has a GraphQL field name conflict between the '{name}' {name_source_1} and the '{name}' {name_source_2}. One of these will need to be renamed."
    )]
    GraphqlFieldNameConflict {
        type_name: Qualified<CustomTypeName>,
        name: String,
        name_source_1: FieldNameSource,
        name_source_2: FieldNameSource,
    },
    #[error(
        "the type of the comparable field '{field_name}' on the boolean expresssion '{boolean_expression_type_name}' is a multidimensional array type: {field_type}. Multidimensional arrays are not supported in boolean expressions"
    )]
    MultidimensionalArrayComparableFieldNotSupported {
        boolean_expression_type_name: Qualified<CustomTypeName>,
        field_name: FieldName,
        field_type: QualifiedTypeReference,
    },
    #[error(
        "the target model '{target_model_name}' of the relationship '{relationship_name}' does not have a boolean expression type defined"
    )]
    ComparableRelationshipToModelWithoutBooleanExpressionType {
        target_model_name: Qualified<ModelName>,
        relationship_name: RelationshipName,
    },
    #[error("the boolean expression type with name {type_name} is defined more than once")]
    DuplicateBooleanExpressionType {
        type_name: Qualified<CustomTypeName>,
    },

View on GitHub (pinned to 724551b9ae)

Solutions

Remove the multidimensional field from comparable fields
Change the field's type to a flat scalar array or JSON if the shape is not semantically 2D
If the underlying column is genuinely 2D, expose it via a non-comparable field only

Example fix

// before
matrix: [[Float]]
  comparable: true
// after
matrix: [[Float]]
  comparable: false

Defensive patterns

Strategy: validation

Validate before calling

fn array_depth(mut t: &QualifiedType) -> usize {
    let mut d = 0;
    while let QualifiedType::Array(inner) = t { d += 1; t = inner; }
    d
}
for f in &be_type.comparable_fields {
    assert!(array_depth(&f.field_type.underlying) < 2,
        "{} is multidimensional; not allowed in boolean expressions", f.name);
}

Type guard

fn is_multidimensional(t: &QualifiedTypeReference) -> bool {
    matches!(t.underlying(), QualifiedType::Array(inner)
        if matches!(**inner, QualifiedType::Array(_)))
}

Try / catch

if let BooleanExpressionIssue::MultidimensionalArrayComparableFieldNotSupported { field_name, field_type, .. } = &issue {
    log::error!("{field_name} ({field_type}) is multidimensional; mark it non-comparable");
}

Prevention

Never mark 2D-array columns as comparable
Flatten or JSON-typing genuinely nested data
Run resolve checks in CI after schema changes

When it happens

Trigger: Declaring a comparable field whose QualifiedTypeReference is a nested array type, e.g. `[[Int]]`, in a boolean expression type.

Common situations: Postgres columns typed as multi-dimensional arrays or nested JSON arrays mapped to nested array types in metadata; schema changes introducing `[][]` types into a type with an existing boolean expression.

Related errors

AI-assisted analysis of hasura/graphql-engine@724551b9ae (2026-08-28). Data as JSON: /api/errors/7428997f6e72936e. Report an issue: GitHub.