Function validateQueryStructure

packages/db/src/query/compiler/index.ts:988–1032

* Validates the structure of a query and its subqueries. * Checks that subqueries don't reuse collection aliases from parent queries. * This must be called on the RAW query before optimization.

(
  query: QueryIR,
  parentCollectionAliases: Set<string> = new Set(),
)

 * This must be called on the RAW query before optimization.
 */
function validateQueryStructure(
  query: QueryIR,
  parentCollectionAliases: Set<string> = new Set(),
): void {
  // Collect direct collection aliases from this query level
  const currentLevelAliases = collectDirectCollectionAliases(query)

  // Check if any current alias conflicts with parent aliases
  for (const alias of currentLevelAliases) {
    if (parentCollectionAliases.has(alias)) {
      throw new DuplicateAliasInSubqueryError(
        alias,
        Array.from(parentCollectionAliases),
      )
    }
  }

  // Combine parent and current aliases for checking nested subqueries
  const combinedAliases = new Set([
    ...parentCollectionAliases,
    ...currentLevelAliases,
  ])

  // Recursively validate FROM subqueries
  if (query.from.type === `unionAll`) {
    for (const branch of query.from.queries) {
      validateQueryStructure(branch, combinedAliases)
    }
  } else {
    for (const source of getFromSources(query.from)) {
      if (source.type === `queryRef`) {
        validateQueryStructure(source.query, combinedAliases)
      }
    }
  }

  // Recursively validate JOIN subqueries
  if (query.join) {
    for (const joinClause of query.join) {
      if (joinClause.from.type === `queryRef`) {
        validateQueryStructure(joinClause.from.query, combinedAliases)
      }
    }
  }
}

/**
 * Processes the FROM clause, handling direct collection references and subqueries.