Budibase/budibase · error · BadRequestError

Column "${oldColumn.name}" is a one-to-many column but "${ne

Error message

Column "${oldColumn.name}" is a one-to-many column but "${newColumn.name}" is not a single user column

What it means

The target column type must match the cardinality of the old relationship. A ONE_TO_MANY relationship can only be migrated to a single user column (BB_REFERENCE_SINGLE). getColumnMigrator throws this BadRequestError when a one-to-many relationship is paired with a multi-user BB_REFERENCE target.

Source

Thrown at packages/server/src/sdk/workspace/tables/migration.ts:138

  if (newColumn.subtype !== BBReferenceFieldSubType.USER) {
    throw new BadRequestError(`Column "${newColumn.name}" is not a user column`)
  }

  if (!isRelationshipField(oldColumn)) {
    throw new BadRequestError(
      `Column "${oldColumn.name}" is not a user relationship`
    )
  }

  if (oldColumn.tableId !== InternalTable.USER_METADATA) {
    throw new BadRequestError(
      `Column "${oldColumn.name}" is not a user relationship`
    )
  }

  if (oldColumn.relationshipType === RelationshipType.ONE_TO_MANY) {
    if (newColumn.type !== FieldType.BB_REFERENCE_SINGLE) {
      throw new BadRequestError(
        `Column "${oldColumn.name}" is a one-to-many column but "${newColumn.name}" is not a single user column`
      )
    }
    return new SingleUserColumnMigrator(table, oldColumn, newColumn)
  }
  if (
    oldColumn.relationshipType === RelationshipType.MANY_TO_MANY ||
    oldColumn.relationshipType === RelationshipType.MANY_TO_ONE
  ) {
    if (newColumn.type !== FieldType.BB_REFERENCE) {
      throw new BadRequestError(
        `Column "${oldColumn.name}" is a ${oldColumn.relationshipType} column but "${newColumn.name}" is not a multi user column`
      )
    }

    return new MultiUserColumnMigrator(table, oldColumn, newColumn)
  }

View on GitHub (pinned to a81a902e9a)

Solutions

Use FieldType.BB_REFERENCE_SINGLE as the target for ONE_TO_MANY relationships
Derive the target type from cardinality: ONE_TO_MANY -> BB_REFERENCE_SINGLE, otherwise BB_REFERENCE
Use migrate() (not getColumnMigrator) which picks the correct type automatically

Example fix

// before
const newColumn = { name: "owner", type: FieldType.BB_REFERENCE, subtype: BBReferenceFieldSubType.USER }
// after
const newColumn = { name: "owner", type: FieldType.BB_REFERENCE_SINGLE, subtype: BBReferenceFieldSubType.USER }

Defensive patterns

Strategy: validation

Validate before calling

if (oldColumn.relationshipType === RelationshipType.ONE_TO_MANY &&
    newColumn.type !== FieldType.BB_REFERENCE_SINGLE) {
  throw new Error("ONE_TO_MANY must migrate to a single user column")
}

Prevention

Map relationshipType to target type: ONE_TO_MANY -> BB_REFERENCE_SINGLE
Let migrate() derive the target type from cardinality automatically

When it happens

Trigger: Invoking the migrator with oldColumn.relationshipType === RelationshipType.ONE_TO_MANY and newColumn.type === FieldType.BB_REFERENCE (multi) instead of BB_REFERENCE_SINGLE.

Common situations: Constructing migration payloads in bulk with a fixed target type without inspecting each relationship's cardinality.

Related errors

AI-assisted analysis of Budibase/budibase@a81a902e9a (2026-08-29). Data as JSON: /api/errors/81cb589f2e17145e. Report an issue: GitHub.