grafana/public/app/features/explore/utils/queries.ts

import { DataQuery } from '@grafana/schema';
import { getNextRefIdChar } from 'app/core/utils/query';

/**
 * Makes sure all the queries have unique (and valid) refIds
 */
export function withUniqueRefIds(queries: DataQuery[]): DataQuery[] {
  const refIds = new Set<string>(queries.map((query) => query.refId).filter(Boolean));

  if (refIds.size === queries.length) {
    return queries;
  }

  refIds.clear();

  return queries.map((query) => {
    if (query.refId && !refIds.has(query.refId)) {
      refIds.add(query.refId);
      return query;
    }

    const refId = getNextRefIdChar(queries);
    refIds.add(refId);

    const newQuery = {
      ...query,
      refId,
    };

    return newQuery;
  });
}