Function computeSubscriptionOrderByHints

packages/db/src/query/live/utils.ts:396–422

(
  query: { orderBy?: OrderBy; limit?: number; offset?: number },
  alias: string,
)

 * be scoped to the given alias (e.g. cross-collection refs or aggregates).
 */
export function computeSubscriptionOrderByHints(
  query: { orderBy?: OrderBy; limit?: number; offset?: number },
  alias: string,
): { orderBy: OrderBy | undefined; limit: number | undefined } {
  const { orderBy, limit, offset } = query
  const effectiveLimit =
    limit !== undefined && offset !== undefined ? limit + offset : limit

  const normalizedOrderBy = orderBy
    ? normalizeOrderByPaths(orderBy, alias)
    : undefined

  // Only pass orderBy when it is scoped to this alias and uses simple refs,
  // to avoid leaking cross-collection paths into backend-specific compilers.
  const canPassOrderBy =
    normalizedOrderBy?.every((clause) => {
      const exp = clause.expression
      if (exp.type !== `ref`) return false
      const path = exp.path
      return Array.isArray(path) && path.length === 1
    }) ?? false

  return {
    orderBy: canPassOrderBy ? normalizedOrderBy : undefined,
    limit: canPassOrderBy ? effectiveLimit : undefined,
  }
}

/**
 * Compute the cursor for loading the next batch of ordered data.