AIKIDO-2026-22244

TL;DR

The AshSql.AggregateQuery.add_single_aggs/5 function rebuilds the outer query when computing aggregates over a distinct query, reconstructing it from query.from.source alone. That reconstruction discards the Ecto.Query prefix metadata where Ash stores the tenant schema for schema-based multitenancy, so the rebuilt query reads from the repository's default public schema. With sequential primary keys, aggregate values and downstream joins can match rows belonging to the wrong tenant. The fix preserves the query prefix so aggregates run against the correct tenant schema.